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IDFK What's going on with my 2.9l. Starts and runs fine when cold, when warm it jerks and starts with misfire... sometimes.


McWillies

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I've had this issue for a while now, but I'm now getting around to digging into it. The problem is weird because it's not definite, but it is only under certain conditions... very specific conditions.

When the engine's cold, it starts up great. Start going down the road and all is well. Get on the highway and a few minutes in, once the engine is warmed up, I'll get a weird "jerk" around the speed it usually shifts into OD. To give an example; I'm going down the highway and then have to slow down to 55 or 60. When I go to speed back up, the truck sorta sputters/jerks. Almost like if it dies for half a second, comes back alive, dies again, so on and so forth. I can either give it more gas and it will power through (issues disappear at WOT) or I can manually shift it into 3rd (go from OD to D). When I'm in 3rd it doesn't happen at all at the same speeds. Continuing the story, I get off the highway and stop at the red light. While I'm sitting at the red light, it's trying to die on me and won't idle for shit, so I have to hold it at a higher RPM (I don't know what RPM because my tach doesn't work, but my foot is barely on the pedal, probably a few hundred over normal idle). The light turns green, I start to take off and the truck is sputtering and jerking, but only if I hold the RPMs at a normal rate and keep it constant (as you normally do when accelerating). If I give it some beans (more like a single bean, it's a 2.9 after all), the issues disappear.
Now let's talk about the starting with a misfire. I have a good example to share. I did some front end work on it recently after a wreck and needed to make it to an appointment at the alignment shop. I had to go down the highway to get there. The same issues I talked about before were happening (dies down at light, yada yada). Keep in mind it was hot as hell out, 90 degrees and sunny. Alignment tech jumps in and starts the truck and it does fine. Gets it on the rack and starts doing his thing (where I go they don't use the electronic stuff for alignments). Since they don't use the computers they make adjustments to get it close, take it for a drive to see how it feels, and come back to make more adjustments. First time he started it up to test drive, everything went fine. He drove it around for a minute, came back and made some adjustments. Second time, it wouldn't start. I could hear him cranking it and the first two or three times, it fired off, but it was really rough and died seconds later. Kept trying and after the fifth or sixth try it would just crank. Like I said before, I've been having these issues for a while so I know the little tricks to get it running. He opened up the door to the waiting room and told me it wouldn't start. I walked out there and told him to feather the gas pedal while it's cranking. Started up with a mean misfire, but he gave it some gas and it cleared up. Took it on the test drive, came back and did his thing, and from then on it started fine (I think he took it on two more test drives). When he was done and I went to leave, it started fine and I drove off.

Now to get to what I've done so far:
A couple months ago I replaced the MAP sensor, thinking that might be the issue. No dice.

The other day I had it in the shop to do the front brakes and decided to investigate this issue again. I remembered about two weeks ago, I got a CEL for a few minutes when it was happening, then it disappeared. Did a KOEO test to check for codes. All clear on hard faults with an 11, but I got a 41 from the continuous memory. Looked it up and that appears to be the O2 sensor. Ran to the parts store, got a new one, and threw it in. The old one had a Ford logo on it, not Motorcraft, so I can only imagine it was the same one as from the factory. Yesterday I drove it home (hour and a half mostly 60mph+). Same issue as far as the jerking when in OD, but it didn't seem to wanna die on me when I was stopped at a light after getting off the highway and when I stopped at the gas station and shut the truck off for a minute, it started back up fine. I also noticed that if I kept the speed about 69-70mph on the speedo (more like 72-73, tires are bigger than stock), it doesn't jerk when in OD.
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From what I've been able to interpret, it seems the jerking happens when I'm in a specific RPM range and the engine is warm, and it's just a coincidence that it always starts on the highway (any driving I do around town at low speeds is for a short amount of time).

I've read the TFI module can cause issues similar to this. When I was doing the O2 sensor I looked at the wires and they seemed fine. Felt around the back of the distributor and the TFI didn't feel melted or deformed.
 


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This is probably going to get ugly before it gets better.
Have you checked the basics? plugs, wires, distributor cap, rotor, air filter? Checked for vacuum leaks?

Cold to hot running. Fuel, cold engines require more fuel. If the amount of fuel isn't reduced as the engine temp rises, it won';t run properly. Sensors to check, ECT and ACT.

O2 sensor, did you look at the wiring harness connector? Mine was super crusty, to the point I probably did not need a new O2 sensor when I replaced it and just needed to clean the connector.

Electrical, almost sounds like a bad ICM/TFI and maybe it is. Or bad coil. They get hot and start messing up.

Really off the wall, I had a loose connection at my fuel pump. It ran fine for bit then starting messing up and finally the fuel pump didn't run. if it sat for an hour or two it would start right back up.

Do you have a vacuum gauge? It will give you some clues about the engine.

I'd put a fuel pressure gauge on it to see if you have the correct pressure. You might even have an injector leaking down and during hot start that's too much fuel.

If you can find a shop with an Sun scope like they used before ODB-II and an old timer that knows how to use it they could probably figure this out fast. Problem is that ODB-II has turned 99% of mechanics into Technicians that mostly follow what the computer tells them to do.

Good Luck.
 

McWillies

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This is probably going to get ugly before it gets better.
Have you checked the basics? plugs, wires, distributor cap, rotor, air filter? Checked for vacuum leaks?

Cold to hot running. Fuel, cold engines require more fuel. If the amount of fuel isn't reduced as the engine temp rises, it won';t run properly. Sensors to check, ECT and ACT.

O2 sensor, did you look at the wiring harness connector? Mine was super crusty, to the point I probably did not need a new O2 sensor when I replaced it and just needed to clean the connector.

Electrical, almost sounds like a bad ICM/TFI and maybe it is. Or bad coil. They get hot and start messing up.

Really off the wall, I had a loose connection at my fuel pump. It ran fine for bit then starting messing up and finally the fuel pump didn't run. if it sat for an hour or two it would start right back up.

Do you have a vacuum gauge? It will give you some clues about the engine.

I'd put a fuel pressure gauge on it to see if you have the correct pressure. You might even have an injector leaking down and during hot start that's too much fuel.

If you can find a shop with an Sun scope like they used before ODB-II and an old timer that knows how to use it they could probably figure this out fast. Problem is that ODB-II has turned 99% of mechanics into Technicians that mostly follow what the computer tells them to do.

Good Luck.
Hey Jerry, I was hoping you'd stumble across this thread. You seem to be a walking encyclopedia for RBVs.

Wires, cap, and rotor were all replaced not too long ago. I checked the wires and none were loose or burnt through. It's been a couple years since I looked at the air filter, when I replaced it. I haven't done a smoke test or anything for vacuum but I've checked all the lines and they're in good shape and tight around the vacuum ports.

What resistance should I see on the ECT and ACT? Voltage when running?

For the O2 sensor, how were you able to look at the connector? To get to the connector I had to reach one hand through the wheel well and one following the trans dipstick. Couldn't see a thing.

Coil was replaced a few months ago. Not for anything specific, I just do too much preventative maintenance. Recently I crimped some new terminals onto the wires and replaced the plastic connector. The connector was broken and the truck would die when I wiggled one wire, but that's fixed.

When you mentioned the injector leaking a little light bulb went off in my head. If I start the truck up and drive around town until it gets up to operating temp, then stop at the store for 30 minutes or so, when I come back it starts up rough and there's a "burning" smell. I'm thinking it's an injector getting stuck open, what do you think? Doesn't happen if I kill it for just a couple minutes (gas station, etc etc) and I figure that's because the injector doesn't have enough time to leak enough fuel.

I don't have a vacuum or fuel pressure gauge, but there's plenty of auto part stores that'll rent them out. Do you know if any of them rent timing lights as well? I've looked online and I can't seem to find one that rents them. I'll bite the bullet and buy one if I have to, it's a good diagnostics tool to have.

You sure are right about modern technicians. If the computer doesn't show it, it can't be the problem. I'm all for technology and computers, but they're supplemental to people. Just because the computer doesn't show an error for something doesn't mean it isn't a problem, it means the computer doesn't have a sensor for it or the sensor isn't working.

Just an update:
I've drove it around some and the new O2 sensor definitely seems to have done something. The highway problem disappeared for almost an entire 1 hr 30 min trip, until right near the end, of course. But the jerking wasn't nearly as bad as before when it did happen. I'm gonna keep an eye on that for now.

I'm gonna do a KOER test when I get the time. Classes start back up tomorrow following spring break and it's almost the end of the semester, so that means final exams!
 

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Hey Jerry, I was hoping you'd stumble across this thread. You seem to be a walking encyclopedia for RBVs.
I'm not that smart, it's that my BII needed a lot of work. :) When i was young I had a street racer and worked on others cars as well.

Wires, cap, and rotor were all replaced not too long ago. I checked the wires and none were loose or burnt through. It's been a couple years since I looked at the air filter, when I replaced it. I haven't done a smoke test or anything for vacuum but I've checked all the lines and they're in good shape and tight around the vacuum ports.
You should check the plugs to see how they look, running rich? all or some? Look for a trace line along the porcelain that would spark going to ground instead of into the cylinder.
You know how to do the wire arcing test? Get out in the dark and lift hood and look for electrical arcs.
I found a vacuum leak at the grommet for the brake booster, you never know.
What resistance should I see on the ECT and ACT? Voltage when running?

For the O2 sensor, how were you able to look at the connector? To get to the connector I had to reach one hand through the wheel well and one following the trans dipstick. Couldn't see a thing.
I replaced the ACT after I cleaned it and the truck improved a little, I didn't test it.
The ECT I did test it but I don't remember the values, I found them on the net.
The O2 sensor wire harness I reached by going through the bottom, my BII has had an engine swap and the harness could be in a place that wasn't put there by the factory.

I'm gonna do a KOER test when I get the time. Classes start back up tomorrow following spring break and it's almost the end of the semester, so that means final exams!
You've probably seen me write this a few times on the boards, check your grounds. Electronics need a common ground or their readings are off. You should have at least a ground going to the frame, and engine from the battery and a ground from the engine to the firewall. I think some BII/Rangers had one from the battery to the core support, it wouldn't hurt to add one if you don't.

Good luck on the exams!
 

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Finally had a chance to investigate.

Pulled the IAC off, cleaned it, put it back on with a new gasket. Tested it with a multimeter and I had 12.3 ohms, which is within spec (7-13 ohms) from what I understand. Tested for continuity between each pin to the housing (individually) to make sure there wasn't a short, came back fine. Had at least 12V going to it (can't remember exactly, 12 and change). Cold starting the engine with the IAC unplugged, it idles at 1700RPM. Cold with IAC plugged in, idles at 3000RPM. If I unplug the IAC while the engine is running, idle drops down to 1700RPM. Plug it back in and spikes and settles at 3000RPM. Once engine is warm, IAC being plugged in or not doesn't change anything, and it sits between 1500 and 2000 RPM at idle.

Tested the TPS, had 5.13V on the 5V reference. Adjusted the screw so that it was at 0.98V at "closed" position, between the signal and ground pins. Moved the throttle by hand and the voltage increased steadily as I did that. WOT showed 4.63V. If I loosened it up all the way, so that there wasn't even tension on the spring, it still idled high.

Found out distributor was loose when I was making sure the TFI connector was fully seated. Checked the hold down bolt and loosened it all the way up by hand... shocker. Pulled it out and it was bent slightly. Threads on it looked fine. Picked up a new bolt and managed to get it in. For anybody having issues getting to it, I used a tiny 1/4" drive "breaker bar" with a narrow head. Tiny 1/4" ratchet had too large of a head and it was pissing me off. Stubby wrench could've gotten it too. Bolt head is 13mm or 1/2". 1/2" I found some sockets fit and some didn't, 13mm is my bet. Tightened it until I could just turn the distributor. Pulled the spout connector then hooked up a timing light and set it at 10 degrees, then tightened it up all the way. Checked timing again just to make sure and it was still on 10 degrees. Put the spout connector back in and checked timing and it seemed to be jumping back and forth by a few degrees. Is this normal?

I checked all my vacuum lines again and they all look good and aren't leaking as best as I can tell. Sprayed them and the idle didn't change, gripped my hand around each port to make sure it was sealed, no changes anywhere.

Oh yeah, almost forgot... Pulled the cluster and one of the resistors on the tachometer board didn't have any solder on it. Soldered it up and now it seems to be working. What does a 2.9l/A4LD redline at in 3rd, when kickdown is activated so it's out of OD and dropped down to 3rd? (fully WOT lol).

Before anybody says it, no, it's not just my tachometer not working right that's tricking me into thinking I have a high idle. Did a KOER test and got codes 41 and 13. The code 41 I expected because my passenger side donut between the manifold and y-pipe is leaking (upstream of the O2). Looked it up and the 13 appears to be a high idle (who'da thunk it), possibly from a failing IAC. Not saying the tach isn't off, but at least I know I'm not totally crazy.

Now bear with me... I'ma take a shot in the dark. Cruising down the highway at 65mph, my RPM jumped from about 3500 to 3900, then back to 3500 and then to 3900, so on and so forth (I could audibly hear the engine RPM changing, not just the tach jumping around). Finally it stayed steady on 3900 and held there. From what I understand there's a vacuum modulator on the A4LD. How possible is it that the vac line is leaking or the modulator has failed, and it's causing a high idle as well as this issue?
Cruising at 60mph on the speedo, it held steady at 3100 RPM on the tach. Tires are 235/75r15 so the speedo is a couple MPH low. Some basic calculations tell me that in 3rd gear (1:1), with 3.73 rear end, at 3100 RPM, I should be somewheres around 70mph (this is only relevant if my trans was actually in 3rd gear, idk if it was).

I forgot to check the ACT and ECT sensors, but the upper rad hose started getting hot after idling for a bit, so the thermostat opened. I know neither of those sensors have anything to do with the thermostat opening, just figured it was worth mentioning.

Somebody please try to make sense of some of this mumbo jumbo.

Edit: Forgot to mention one thing. If I take my foot completely off the accelerator at about 23-24mph it doesn't slow down. Holds that MPH and an RPM of about 1900 ("idle").

Edit Edit: Took it for a little test drive/pizza run and it's now idling a hair under 1500RPM at all times. It had been sitting for a week or so previously and earlier today I drove it an hour and a half. Next time I cold start I'll see how she acts.

I keep remembering things: I also checked the vacuum line going to the FPR (suspected it might be acting up). It was dry, no sign of fuel.
 
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First fix the exhaust leak and check the vacuum line to the modulator.
Get a hand held vacuum pump and pull a vacuum on the modulator line to check it.
Always fix what you know is broken first.

"Edit: Forgot to mention one thing. If I take my foot completely off the accelerator at about 23-24mph it doesn't slow down. Holds that MPH and an RPM of about 1900 ("idle")." Is this while in gear? This might be a modulator or kickdown issue. Also could be a sticky throttle, everything from the pedal to the TB.
 

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I'll check the vac line and hopefully take care of the exhaust leak this weekend.

I talked to a mechanic at the local Ford dealership that I've dealt with in the past; he's not a "diagnostics technician" like many dealership workers nowadays, he knows a thing or two. He recommended I replace the IAC, so I ordered one at the NAPA and I'll get it swapped out this weekend. Was leaning towards replacing it and him recommending I do just pushed me over the edge. It's a bad habit, especially for a college student, but it bothers me to put old parts back on.

I've been thinking alot about how the IAC system works and was reading up a little bit and I was hoping you could clear some things up for me. Just my curiosity going wild per usual.
Anyways, on to the questions. I understand how an intake system works; the intake valve opens while the piston moves downwards, and the vacuum in the chamber causes air to be sucked in through the intake port, yada yada. So, in an intake system that uses an IAC, is air always flowing into the IAC, but only makes its way past and into the intake manifold when the ECM tells it to open the valve? I'm pretty sure the two smaller ports on the bottom of the TB are where the IAC pulls in air... So if the butterfly on the TB is closed off, then the air is naturally sucked through those two ports and into the IAC?
Now let's pretend the IAC valve is stuck open (or isn't sealing properly when it's supposed to be closed). The engine will suck air in through the throttle body as it opens, the same as it usually does, but there will be "excess" air being sucked in through the IAC, correct? Almost as if it were dual throttle bodies, but one was small and one was big... and of course the small one is stuck open.
Just a couple more questions about how the ECM controls the IAC. Is it used at all times when the engine is idling? Specifically I'm asking if at all coolant temperatures the IAC is used to control idle. Seems like I remember seeing that the IAC is no longer used when the coolant reaches a certain temperature, but maybe I'm remembering wrong. Last question. Does the ECM adjust idle RPM (through the IAC) based on coolant temperature? For example, the engine is cold and started up. The ECM sees the low coolant temperature and opens the IAC some amount (is this amount based on real-time or predetermined values?) to allow more air in and raise the idle to help the engine warm up quicker.

Now, as for the questions you asked. Yeah, trans is in drive. I'm thinking it might be the modulator or kickdown. Could be a TB issue as well, but it seemed smooth when I was opening and closing it while testing the TPS the other day. Didn't look gunked up or anything either.

Thanks for the help Jerry, I'll be checking back in.
 

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I don't know specifically how/when the ECM controls the IAC.

This is all theory out of my old brain...
Generally, cold engines use more fuel and then the ECM leans out the mix as it warms up. ECM reads ECT for engine temp.
By letting more air in through IAC the ECM could raise the idle speed without movement of the TB. Good thing as the TB is manual on the BII instead of fly by wire. So cold engine, IAC opens and the ECM sends more fuel and you get the normal high cold idle. As the engine warms up the ECM starts closing the IAC to lower the idle and reduces fueling.

So lets speculate on your hot running issue, engine hot, stuck IAC is like a vacuum leak. ECM can compensate sort of by adding more fuel or maybe not depending on other factors (exhaust leak, possible second vacuum leak) and may over/under compensate and cause poor running.

I may be completely wrong on all of that... and to complicate it the ACT, O2, TPS and MAP sensors also are in play.
 

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This is all theory out of my old brain...
Old brains are usually the most helpful in my experience, at least when it comes to cars :icon-thumby:

Yesterday I stepped outta the apartment to get some fresh air... I guess it was fresh, maybe I breathed in a trillion COVID-19 germs. Anyways, took ole Betsy down the road and jumped on interstate for a few miles just to stretch her legs some. IAC is plugged in (contemplated leaving it unplugged after it was holding my RPM at 3k, but decided against it) and my idle was steady just under 1500 RPM. Engine was cold, hadn't been started in about three days. After driving to the next exit, turning around, and driving back, the idle RPMs were still at just under 1500. Stopped at the gas station and went in to get a drink, came out and she started up fine, with the same 1500 RPM idle of course. She usually does start up fine if sitting hot for just a few minutes. It's when it's been about 20 minutes or more that she likes to complain (heat soak issue or leaking injector, like you pointed out before). Hmm.... interesting. From my many years of experience..... reading online forums and documentation :icon-rofl:, I'm leaning towards a possible ECT not telling the ECM that the engine is warmed up, so it can drop the idle. But, wouldn't a bad ECT sensor come up on a KOER test? I know alot of the old timers don't like to trust the computer diagnostics, especially the ODB1 considering it's limitations. I understand why though, like I said, they have limitations and aren't always accurate.

I plan on picking up a gauge to test fuel pressure and look for a leaking injector. Question: Can I use a plain fluid pressure gauge or does it have to be a "fuel pressure tester gauge" diddlybob? I can pick up something like this for cheaper, and if it'll work just as good, I'm more than happy to walk around with an extra bill in my wallet.

Also gonna pick up a one-wire coolant temp sender for the dash gauge. I know it's an idiot gauge, but it gives me at least some feedback. Ever since the truck sat for a month after the wreck, the gauge jumps around like a squirrel in the tree tops. I know there are two separate sensors for the ECM and dash gauge, just want to get the one for the gauge replaced so I can have an idea of my coolant temp.
 

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No idea if the ECT trips the money light or not. You could just pull the connection and see.
A fuel pressure gauge will handle fuel, meaning fuel will not damage it. One thing I didn't know until I bought a fuel pressure gauge is that there is fuel rated teflon tape, it's yellow not white.
 

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Got a good bit done this weekend.

Pulled the old IAC off and bolted up the new one. Not much change in the idle, which I can't say I'm surprised about. Started checking for vacuum leaks again and, this time, instead of just checking the lines, I listened. Could hear a pretty big leak on the passenger side. Felt around the PCV valve, IAC, TPS sensor, and TB. Pulled the PCV valve to make sure it was all fine, was in good condition. Decided to go ahead and pull off the throttle body, as I was pretty sure that's where the leak was coming from. And if not the TB, then the manifold itself, but I looked all around the base of the manifold and it didn't look like the gasket was blown out anywhere. Checked the bolts and they were all tight. Got the throttle body off and there was the normal sludge on it, but there seemed to be an oil/fuel type mixture in the intake. Smelled like fuel but looked and felt like thin oil. The gasket looked to be in good shape, so I was trying to be careful with it. After finally getting it unstuck from the TB, I pulled it off and there was that same fluid puddled up in between the TB and gasket (in the little "v" groove deals). The gasket looked over-sized. The hole for the throttle opening was about an 1/8" too big all the way around. I went ahead and cleaned off the throttle body then moved to the manifold/y-pipe situation. Was gonna have to wait until Saturday before I could run to the store. Fought with the manifold for a bit and decided to call it a night. Almost forgot, I also checked the vacuum modulator on the trans and the line was in good shape all the way to the manifold.

Got up the next morning and went to O'Reilly's. Picked up a donut gasket (more on this later) and a roll of gasket material. Got back and cut out a new TB and TPS sensor gasket. Tightened up the TPS. Made sure the mating surfaces were nice and clean and bolted up the TB. Got two of the vac lines on the bottom connected, then realized I couldn't get the one that goes to the PS of the manifold on because it was too short and didn't have enough flex. Loosened up the TB again and slipped the hose on, then tightened it up for good. One thing checked off the list.

Moved on to the exhaust again, after a few hours on one of the flange bolts, I finally managed to twist it off, leaving half the bolt in the exhaust manifold. Mostly expected that to happen. Couldn't get a drill in there so I looked for other options. Made four small rectangular mounts, two to go on top of the manifold, and two to go on the flange on the pipe, and was gonna clamp everything together with that. Ended up finding out about the split-flange mounts and opted for that.

Was gonna have to wait until Sunday before I could go pick one up, so I started pulling my door panel off to look at my window regulator/motor, had some issues with it going up. Was getting pissed off and decided to call it. Was about 6PM and I hadn't eaten anything since breakfast.

Now today, Sunday. Woke up and went to AutoZone and picked up a 2-1/4" split-flange. Didn't think the bolts would be long enough, so I picked up some 3/8 x 3-1/2" bolts and nuts to match from Tractor Supply. Made it back and used a recip saw to cut the other manifold bolt and free everything up. I had already tried getting it loose and it just wasn't happening. The other one was already broke off in the mount and I wasn't using those holes anyways, so no need in fighting it. Got it off and started trying to pry the y-pipe back enough to get the donut in there. Right about that time my grandpa walked out to the shop, so I asked him to help. Got a breaker bar to pry with and a cheater pipe for extra persuasion. He pryed it back enough for me to get the donut in... but it didn't fit. Pulled it back out and started thinking. He asked me a few times if there even needed to be a donut there, and I'll be honest, I don't really know. Looked at the driver's side and it doesn't have one... But I also found out, after doing the passenger side, that driver's side leaks too. Go figure. It wasn't leaking before, but I figure there's added pressure on that side since the passenger side is sealed up. So, I ask you the same question: Does there need to be a donut gasket in between the y-pipe and the manifold? The manifold has a nice inward bevel and the pipe is beveled outwards. I ended up grinding down the donut gasket to give it more of a bevel and got it to fit as best as I could. Another hour of fighting to get the bolts, nuts, and washers on and it was tightened up. Before I messed with anything, the passenger side was completely loose and the exhaust piped moved all over the place, so it was basically an open manifold on the passenger side. I didn't try to move the driver's side around, but I'm willing to be it's the same thing.

Towards the bottom of the first post in this thread is a picture of a guy's y-pipe and manifold bolted together, with no donut gasket. Do you have gaskets there?

I had also replaced the single-wire ECT sensor and it didn't fix my gauge, so I pulled the gauge out of the cluster to check things out. It seemed fine, but I don't really know what to look for to be honest. Cleaned off the long "pins" with a wire brush and threw it back in. Still doesn't work, pinned at H when warm now lol. Also pulled the tach out to check my soldering. I don't know if I was smoking crack when I soldered it or what, but I think Helen Keller could've done it better. Got the old solder off and melted some new solder onto it. Happy with it now. Got everything put back together and started it up. Idle was high at around 2100 RPM, but it hadn't been started since Friday. Let it warm up for a few minutes and the idle dropped down some, to about 1900 RPM. Was filling the shop up with fumes so I shut it off. Still had the door panel apart from before, so I checked and couldn't find anything wrong with the window system, other than it would "skip." Looked at some pictures a few minutes ago and I'm thinking the teeth came off the gear that's on the motor. I can hear it coming on when I push the button, just doesn't moved the window. Got it warmed up and drove it some. Idles about 1200 RPM now and runs alright, but I'm still not sure about the cruising RPM, hasn't changed much. Idk. Gonna keep driving it this week and see if the computer calculates in all the new information.

Oh yeah, before I picked up all the tools and cleaned up, I threw a timing light on it just to make sure it was all good from last weekend. Dead on where I set had set it... that's good.
 

JerryC

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That's a ton of work you got done.
I don't know about the exhaust, paid a shop to mine.
I did have the gasket between the lower and upper intake fail, I had it at the shop for something and it went bad. The showed it to me and it was hard and brittle, just died of old age. Might check that.
The temp gauge, are there two parts for the sender? One for gauge and one for idiot light? Might be you have the wrong one. When I got my BII the oil pressure sender wire was hanging loose. Hooked it up and the oil light lit, "oh shoot" moment there. Previous owner installed the wrong sending unit.
 

McWillies

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It is possible the intake manifold gasket failed, but best I can tell there aren't any leaks coming from it. Be honest with you, I really don't wanna pull the manifold off unless it's my last option. I'm fairly comfortable pulling off stuff that I know I can still make work if a bolt breaks off or something like that happens, but pulling the manifold is that next leap into the rabbit hole. One bolt breaks off and now I have no choice but to dig it out, then I dig that damn thing out and be guaranteed I'll mess up the cast iron threads... I'll spray around the mount and see if the engine revs up.... and if it does I might pretend I didn't hear anything :icon-rofl:

As for the exhaust, I found this diagram that shows the y-pipe and flange connection, and it doesn't show a donut in between there. On the flanges that do need a donut, it shows one, so I figure it would show one here as well if it was needed.



On the temp gauge: There's two sensors. The two-wire sensor which, from what I understand, the ECM pulls data. Then a one-wire sensor/switch/sender/doomahicky that's connected directly to the cluster. I replaced the one-wire sensor with a new one. It grounds through the engine block with the threads, then has the signal wire. Didn't use any teflon tape for this reason. I think I'm just gonna pick up a cheap gauge at the auto parts store or order one from online. I've been resisting just because I like the stock look of having all my gauges in the cluster, but eventually I have to bite the bullet if I want gauges that give me accurate information. I can mount it on the little plate just under the light switch, to the left of the steering column. Won't be intrusive but I'll still be able to see what my engine is doing.
 

alwaysFlOoReD

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I'm pretty sure the exhaust manifold has an integrated donut.
 

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I wouldn't pull the manifold, I'd spray around the mating surface with brake cleaner and see if the idle changes.
Did you put a vacuum gauge on it?
 

McWillies

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I'm pretty sure the exhaust manifold has an integrated donut.
Sorry, but what do you mean by integrated? As in the manifold and y-pipe seal themselves, and a donut gasket isn't necessary? That would make sense.

Did you put a vacuum gauge on it?
Didn't have a chance to this time, but I'll try to remember for the next time, which'll hopefully be this weekend. I can definitely tell a difference after doing the work on it. Every time I come to a stop I think the truck died on me, but it's because of how much quieter it is and the lower idle... Also much smoother idle than before.
 

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Welp... Blew a hole in the radiator, engine overheated, and now I'm fairly sure I have a blown head gasket. Put a new radiator, cap, and thermostat in and it won't stop bubbling. Tried all the known tricks for bleeding and none have worked. With the cap off there's bubbles in the rad and with the cap on there's bubbles in the overflow. Rev the engine up a bit and there's more bubbles. Taking it for a drive, it doesn't overheat or smoke, but it pushes coolant into the overflow and by the time I make it back and park the truck and leave it idling, the overflow is bubbling like crazy. Left it idling for an hour and a half yesterday while I sat there, checking it every 30 seconds or so, and it bubbled the entire time. I'm thinking exhaust gas is blowing through the head gasket, but not much coolant, if any, is making its way into the chamber. Oil looks perfect and there's no smoke from the tailpipe. Weirdest thing to me is that it doesn't overheat. Letting it idle for an hour and a half, the temp gauge rose, thermostat opened and temp dropped, then rose up to 12 o'clock and held steady the entire time. Same situation when I took it for a 20 minute test drive this morning, held steady the entire time. I'm gonna pick up one of those kits to test the coolant for exhaust gases and see how that turns out. Sorta hope it does lead to a bad head gasket because then I'll at least know, instead of where I am right now.

Jerry, if you're putting two and two together... I guess my coolant temp gauge wasn't bad after all. Never saw any other signs of overheating whatsoever. Put a new thermostat in with the radiator because the old one wasn't opening when I tried bleeding the system at first. Tested the old one in boiling water and it didn't budge, so it was stuck closed. I figure it has been for a while now and I just assumed the gauge was being wonky because I didn't see anything else that would make me think it was overheating. Major mistake on my part. I've learned in the past that assumptions are a dangerous game, but I didn't listen to those lessons this time.

Oh well. If I confirm it's a head gasket, I'll be pulling the upper and lower intake, valve covers, exhaust manifolds, and heads off. Use new gaskets on everything I pull off and have the heads machined, lapped, and tanked. Depending on how the time frame treats me, I'm hoping I'll be able to clean up the valve covers and paint them. Maybe have time to fight with dropping the oil pan so I can re-gasket that and fix part of my oil leaking issue.

Last thing I'm really hoping is that the overheating didn't hurt the trans. The trans cooler is tied into the radiator, so a hot engine more than likely means a hot trans. Can't lie, I'm a bit bummed, but also looking forward to it. I think most of the people here can relate to how satisfying it can be to pull apart an engine and put it back together knowing it's in better shape than ever.

Looking on the bright side, I'll rebuild the injectors while I have them out. Also, still hear a major vacuum leak on the passenger side near the intake manifold, so hopefully that'll be solved when I put it back on with new gaskets.

Just wanted to say as well, I know this'll be an involved process, but I've done all the work on that damn truck so far and I'm not ready to let a shop have all the real fun. Definitely gonna be a big undertaking for me, but I can't learn unless I do it :icon-thumby:
 

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Not much for me to say, except bummer.
I "think:" the trans will be ok, change the fluid obviously.

If it was me, and if I could, I think I'd do a full rebuild. Or at least a hone, re-ring, oil pump and pickup and bearings.
I think I read somewhere the 2.9's cams wear over time, might be wrong. But given that the lifters like to make noise, a new cam and lifters too.
But if money and time are limited the top end rebuild will get you going again.
 

McWillies

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I get where you're coming from, but I have to cut it off somewhere or I'll end up spending too long and too much money. Had some things to take care of this morning so I didn't get started on the teardown until about 3 o'clock. Before that I spent an hour or so printing out schematics and guides so I didn't have to mess around with looking online and waste time.

Once I got started things went really smooth. Got the alternator pulled off and a/c compressor unbolted and out of the way in about 30 minutes or so. Then I spent some time just looking around and thinking. Disconnected all the vacuum lines and electrical connectors holding in the upper intake. Loosened up all 6 mounting bolts, then I unplugged the TPS (did this on purpose of course... we all know the TPS has to stay plugged in until the manifold bolts come out :icon-twisted:). Got the little mounting plate at the rear of the manifold, for the trans vacuum line and a/c hose, unbolted too. Pulled the manifold and there was fluid pooled around the intake ports and on the gaskets. Same stuff that was in the throttle body, no surprise there. I'm not completely sure what it is. Too brown to be fuel and too thin to be oil. Maybe excessive blow-by or could even be from worn out seals on the valve stems. Anyways, moving on. Started to disconnect the fuel lines on the driver's side (to the FPR and one to the rail I think, I forget), but didn't have a disconnect tool, just went on to something else instead of fighting with it. Goofed around with the electrical connectors on the injectors and got all of them disconnected. Labeled each connector with its corresponding cylinder so I know where they go. Moved on to the passenger side valve cover because it's more of a PITA to get to and I like to get the more annoying stuff done first. Got it off and got to peek inside the engine for the first time. Looks really clean to me. No gunk built up in the head and all the push rods looked straight. No loose rockers or anything else out of the ordinary. Whoever had the covers off last definitely wasn't shy with the red RTV. I didn't get any good pictures of the guts but I'll be sure to tomorrow for my reference and to post here.

That's as far as I got today. Got 3 hours of sleep last night because I stayed up late looking at parts and researching, then woke up early because I was excited to work on it. Was a solid three and a half hours but half of it was spent walking back and forth to and from the tool box. Now I have it mostly figured out as far as what I need and such. Pisses me off that there's SAE and metric sizes scattered throughout. Personally I have more to work with on the SAE side, but please just pick one and use it consistently.

Tomorrow I'll run to NAPA and get a fuel line disconnect tool and hopefully they'll have a T55 Torx socket so I can actually pull the heads.
 

Cees Klumper

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Having read this thread, and having only very limited experience working on my own '90 Bronco II, some thoughts:
  • I also rebuilt my injectors with new seals but that did not help anything; then got 6 rebuilt injectors for $59 delivered (ebay, company called CS performance as I recall) and that did make a huge positive difference in how the engine runs
  • vacuum leaks can cause major issues on this motor, so you are right to eliminate those
  • there is a procedure for calibrating the intake butterfly stop bolt to achieve proper idle. Many, me included, mistake that bolt for the way to adjust idle, and mess up the whole idle regulating system (which should be controlled by the IAC and ECM). I found it here somewhere in a post, can't find it now but it was something like, get engine to operating temp, unplug IAC, adjust the stop bolt, keep idle at 2,000 rpm for 2 minutes, plug IAC back in and idle should be at around 750 or so rpm, if not repeat adjustment procedure. Best look it up as I probably don't remember accurately
  • intake manifold gaskets can leak causing issues. You will be replacing those, which could rule out one more cause for your issues
Good luck, you will for sure get there. After I fixed a couple of issues after getting my B2 last October, it's running really sweet and strong now. Properly tuned, these engines are good powerplants.
 

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