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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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Age
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Location
Louisiana
Vehicle Year
1989
Vehicle
Ford Bronco II
Engine Size
2.9l
Suspension Style
4wd
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.
Appreciate the information sir. Not sure if you recognized, but I'm the one that asked if you put 19lb injectors or stock ones back in. I saw your response as well, noted. I'll look at my injectors and see what kind of shape they're in. Got the heads off today and there's no gunk at all built up around the bases of the injectors, look clean. I'm aware of the bolt on the TB. I've read it should be adjusted so that the TPS reads around 0.9 volts, but other places I've seen between 0.7 and 0.9 volts. I'll fool around with that later on. My lower intake plenum gasket looked to be in good shape, so I figure the upper gaskets were the the ones leaking.
 


McWillies

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Messages
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Reaction score
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Age
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Location
Louisiana
Vehicle Year
1989
Vehicle
Ford Bronco II
Engine Size
2.9l
Suspension Style
4wd
Worked from about 10 this morning until 5 this evening. Here's the update.

Started off by running to NAPA and picking up a fuel line disconnect tool and a T55 socket (thought I'd need it, but the bolts were regular hex).

Made it back and started pulling stuff apart. Got the driver's side valve cover pulled off. Found something pretty interesting... I have a new style head on the driver's side and an old style on the passenger's side. No doubt someone's had this top end apart at some point, but I didn't think I'd find two different heads.

Moved on to pulling the lower plenum. First I went ahead and disconnected the fuel lines. Then I looked at the distributor for a bit trying to decided if I really had to pull it. Decided to try without pulling it and, surprise, I couldn't get the two rear-most bolts out all the way with it in. Pulled all except the #1 plug wire, unbolted the hold-down bracket, then pulled it out. Pulled the plenum bolts, reverse torque sequence, then pulled and laid them out. Plenum came out without a problem... Check out the crocs, a working man's shoe.

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Moved on to pulling the passenger side head. Loosened up a couple bolts for the alternator bracket and pulled that off. Loosened up the rocker arm shaft bolts then went a couple turns at a time on each one until there wasn't any more pressure on the shaft. Zipped them off with the impact driver and laid them out. Lifted the rocker arm and shaft assembly off of the head and sat it down with the bolts, then I pulled the push rods out one at a time and laid them down the same way. Unbolted the exhaust manifold at the y-pipe and slipped the hose that goes to the hair box off. Pulled the spark plugs and unbolted the transmission dipstick tube. Bout time to remove the head. Reverse torque sequence broke each bolt loose, went around a few times in that sequence and loosened each bolt up by a couple turns by hand, then I used the impact to get the front 6 fully loosened and the rear 2 I finished by hand (impact wouldn't fit). Pulled each bolt and laid it out. Time to pull the head. Couple taps with a rubber mallet and it broke loose. Pulled it off and immediately noticed coolant in all 3 cylinders.


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Wiped the surface off real quick and couldn't see any cracks. Valves look good to my untrained eye. When I pulled the spark plugs cylinders 1 and 2 looked lean and 3 looked on the richer side, matches up with the exhaust valves to my untrained eyes.

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Moving on to the other side. Couple bolts holding a bracket for the power steering to the head. Got those out and undid the ground wire attached to the back of the head. Oh yeah, the oil dipstick tube. It was attached to the power steering mounting bracket, unbolted that and pulled it out. Followed the same steps as on the passenger side head. Only different was the manifold bolts at the y-pipe. Had to fight with them and then finally decided to use way too many extensions, a breaker bar, and a cheater pipe to twist the heads off. I'll dig them out later on. Got the head pulled off and there was coolant in cylinder 6, other two were dry. In the picture it looks like #5 had some coolant, but that's just some oil that dripped down.

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Glanced over the head and didn't see any cracks. Cylinder 6 intake valve looks rough, similar to but worse than cylinder 3. Interesting.

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Forgot to snap a picture of the top side. Have a few questions, but I can't attach any more images to this post, so I'll do another with a full view of everything laid out and some pictures of the numbers stamped onto the heads. Sorry about some weird formatting, but I'm too tired to fix it.
 

McWillies

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Joined
Aug 30, 2017
Messages
24
Reaction score
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Age
21
Location
Louisiana
Vehicle Year
1989
Vehicle
Ford Bronco II
Engine Size
2.9l
Suspension Style
4wd
After I got both heads pulled, I got curious to see if the newer style one was stamped 86TM or 89TM. Looking at it, it's stamped 86, same as the other, older style one.

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Looked around a bit more and found just "89" stamped on the new style one and just "85" stamped on the old style. Are these model years by chance?

New Style:
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Old Style:
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Anybody have a newer style head they'd be willing to sell and ship out ASAP?

Here's a picture of everything that I pulled off::

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And the block sitting in there topless. I have some cleaning to do:

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