•  

    Click HERE to join our forum and participate in the discussions.

     

no power under load


LeBronCo

Member
Joined
Jan 10, 2021
Messages
156
Reaction score
19
Points
18
Location
North County San Diego
Vehicle Year
1987 and 1986
Vehicle
Ford Bronco II
Suspension Style
4wd
My credo
Life is more fun if you own a Ford Bronco II
87 2.9. Checked all sensors, spark, fuel. Found rust in tank so replaced tank, sending unit, both pumps and filters. Checked injectors; ok there. Here's what is happening. It starts, idles and revs fine. Pulls away in first gear ok. Second, plus/minus ok. Third gear with a little incline and it feels like its plugged up. Will not pull. It feels like it fires unevenly almost like it's only running on 4-5 cylinders. Forget fourth gear. WTH?
 


Uncle Gump

Moderator
Forum Moderator
Joined
Mar 4, 2020
Messages
539
Reaction score
205
Points
43
Location
Ottawa IL
Vehicle Year
1986
Vehicle
Bronco II
Suspension Style
4wd
Is this the same truck you've been working on for a couple months?

Have you checked for restricted exhaust?
 

LeBronCo

Member
Joined
Jan 10, 2021
Messages
156
Reaction score
19
Points
18
Location
North County San Diego
Vehicle Year
1987 and 1986
Vehicle
Ford Bronco II
Suspension Style
4wd
My credo
Life is more fun if you own a Ford Bronco II
Yes it is. I had to wait for parts. I initially ordered the tank, etc. from LMC. I called after 2 weeks and then I was informed the tank was on back order so I went to Rock Auto and had everything in 4 days. I was thinking a bad cat. I watched a video on YouTube where a dirty MAFS was the problem. The tricky that about this one was the MAFS was giving off a good reading. I'll check both and see if either one help.
 

Uncle Gump

Moderator
Forum Moderator
Joined
Mar 4, 2020
Messages
539
Reaction score
205
Points
43
Location
Ottawa IL
Vehicle Year
1986
Vehicle
Bronco II
Suspension Style
4wd
Well good luck...

A plugged cat is fairly easy to diagnose... google testing for restricted exhaust with vacuum gauge.
 

LeBronCo

Member
Joined
Jan 10, 2021
Messages
156
Reaction score
19
Points
18
Location
North County San Diego
Vehicle Year
1987 and 1986
Vehicle
Ford Bronco II
Suspension Style
4wd
My credo
Life is more fun if you own a Ford Bronco II
Had the Cat checked out and it was OK. Now the B2 is at Corey Holmes' shop in Vista Ca.
 

LeBronCo

Member
Joined
Jan 10, 2021
Messages
156
Reaction score
19
Points
18
Location
North County San Diego
Vehicle Year
1987 and 1986
Vehicle
Ford Bronco II
Suspension Style
4wd
My credo
Life is more fun if you own a Ford Bronco II
Seems like this little gremlin has found a great hiding spot. All that I've done so far: new tank, sending unit, pumps, filters, map sensor, coolant temp sensor, ACT sensor, new distributor, TPS, wires, plugs (gapped & timed), O2 sensor, muffler, back pressure tested, fuel pressure tested (standstill & running), ran a few cans of Seafoam through it. What's still going on: Starts fine, idles/revs fine. 1st gear it pulls ok, second gear pulls ok, 3rd gear it starts to struggle making power, same with 4th. Downhill it runs batshit crazy. Any kind of grade not happening. I'm beginning to wonder if the spark is not advancing. Maybe the weights are getting hung up. How can a motor start up quick, idle/rev smooth and not operate under load?
 

JerryC

Active member
Joined
Apr 10, 2014
Messages
721
Reaction score
98
Points
28
Vehicle Year
1988
Vehicle
Ford
How can a motor start up quick, idle/rev smooth and not operate under load?
Aside from what you listed;
vacuum leak, low compression, worn cam lobes come quickly to mind.
off the wall, retarded cam timing via a loose timing chain.
 

LeBronCo

Member
Joined
Jan 10, 2021
Messages
156
Reaction score
19
Points
18
Location
North County San Diego
Vehicle Year
1987 and 1986
Vehicle
Ford Bronco II
Suspension Style
4wd
My credo
Life is more fun if you own a Ford Bronco II
Checked for vacuum leaks and compression is at 185 +/- all around. I guess next is timing chain? Only 130k on the motor.
 

tw205

Active member
U.S. Military - Veteran
Joined
Jan 23, 2011
Messages
332
Reaction score
124
Points
43
Location
Bronson michigan
Vehicle Year
1985
Vehicle
Ford
Suspension Style
4wd
Timing? I see you have a new distributor.
 

JerryC

Active member
Joined
Apr 10, 2014
Messages
721
Reaction score
98
Points
28
Vehicle Year
1988
Vehicle
Ford
Did you put a vacuum gauge on it?
Here's a crazy one, did you check the air intake for obstructions? Rat nest, etc... Sounds crazy but my wife's mustang had a small paper bag and empty cigarette pack in the air box. That could have been a gold ole american auto worker but it may have gotten sucked in there, I don't know for sure.
 

LeBronCo

Member
Joined
Jan 10, 2021
Messages
156
Reaction score
19
Points
18
Location
North County San Diego
Vehicle Year
1987 and 1986
Vehicle
Ford Bronco II
Suspension Style
4wd
My credo
Life is more fun if you own a Ford Bronco II
Haha, That's pretty funny Jerry. I have checked all that stuff. 'two more things I'm doing on my own before I give it over to the "experts". One is I'm making a bypass pipe for the Cat. Just taking 'em out and putting this piece in their place. Second is replacing the EGR. These are both relatively cheap and should improve performance. If they don't solve the problem, then I may have a bigger one, like maybe a bad motor. Hard to believe with only 130K on it.
 

JerryC

Active member
Joined
Apr 10, 2014
Messages
721
Reaction score
98
Points
28
Vehicle Year
1988
Vehicle
Ford
Haha, That's pretty funny Jerry. I have checked all that stuff. 'two more things I'm doing on my own before I give it over to the "experts". One is I'm making a bypass pipe for the Cat. Just taking 'em out and putting this piece in their place. Second is replacing the EGR. These are both relatively cheap and should improve performance. If they don't solve the problem, then I may have a bigger one, like maybe a bad motor. Hard to believe with only 130K on it.
I think I remember you bought it used, if yes then you just never know how it was treated.
Even so Ford used to build their engines with rubber valve stem seals and nylon covered time chain gears., Both of those deteriorate at 80-100K, if the oil isn't changed regular and early they come apart sooner.
The valve seals clog the oil pump pickup the timing chain usually comes apart in bigger chunks.
If the pump gets clogged you lose pressure and flow and you get wear on the bearings and potentially cam lobes, pushrods , rockers that rob power.
I'm not sure the BII engines had those, but my neighbor with 90's era Ranger had his oil pump clog with one or both of them.

IF... you had a nylon covered timing set when the nylon falls off you get slack in the set. You can get a quick idea by looking at distributor rotor. Move the engine until the rotor moves and stop and note the timing pointer on the balancer, then move it back the other way until the rotor moves again and recheck the balancer. You can then use that distance to get an idea how muck slack is in the chain. I don't know what is normal for a 2.9 but somebody here will know.
 

LeBronCo

Member
Joined
Jan 10, 2021
Messages
156
Reaction score
19
Points
18
Location
North County San Diego
Vehicle Year
1987 and 1986
Vehicle
Ford Bronco II
Suspension Style
4wd
My credo
Life is more fun if you own a Ford Bronco II
The truck is a 9.5/10 on the exterior and interior. Amazingly well preserved for its age. So I'm assuming they took good care of it. It's a two owner B2 with me as the second owner. If the timing chain nylon components are worn wouldn't I hear some kind of racket from its location? Did I mention it's getting piss poor gas mileage; 8-10mpg.
 

JerryC

Active member
Joined
Apr 10, 2014
Messages
721
Reaction score
98
Points
28
Vehicle Year
1988
Vehicle
Ford
Mine was not that nice but it had just over 100K. But a couple of bad owners and...
One day I'm looking the motor and see a knock sensor but I don't see the wiring harness. I looked around quick but nope.
Then I saw some other telltales, ground wire loose, hoses routed oddly, etc..
Aha, they stopped putting knock sensors in at 87, I have an 88. Junkyard motor...

For the timing chain, it might make that much noise, not as much as tapping lifters and clicking injectors and engine fan.
 

LeBronCo

Member
Joined
Jan 10, 2021
Messages
156
Reaction score
19
Points
18
Location
North County San Diego
Vehicle Year
1987 and 1986
Vehicle
Ford Bronco II
Suspension Style
4wd
My credo
Life is more fun if you own a Ford Bronco II
JerryC,
A little backstory. I live in North County San Diego. This all started while driving south on the 15 Fwy. Just as I was about to exit on Gopher Cyn. the truck seemed to just power down like I took my foot off the gas and dropped speed from 55 to 35mph. When I turned onto Gopher Cyn. there is a slight grade and I could barely make it up to 30mph; had to stay in 2nd. the whole way. Since then I've been methodically going through the checklist and replacing what seems at best questionable. One item I forgot to list in my 3/16 post. I replaced the ECM also. Question about a faulty timing chain. If it were bad would the motor still be able to rev smoothly at standstill or would it only affect the motor under load? Why am I also getting such poor gas mileage. Ya know I think I had an easier time figuring out my teenage daughter than this bugger. LOL!
 

JerryC

Active member
Joined
Apr 10, 2014
Messages
721
Reaction score
98
Points
28
Vehicle Year
1988
Vehicle
Ford
That's a mess. The problem with these old vehicles is that good diagnostic tools are hard to find, and that leads to the parts cannon being fired.
Now with with cheap crap parts being made you are really suspect on getting good parts. This leads to the false sense of security in that new=good.
If you don't watch South Main auto on Youtube, you should. He's a good teacher of diagnosing problems and drives the above points home.
Worst comes to worst you might tow it to his place, others have.

As for cam timing, getting the cam timing wrong will lose power, that much power? I don't know. A couple of degrees on small block Ford could lose you 20-40HP easy.
on 2.9L I don't know.

Crap MPG is from no power. You push the pedal down the TB opens and the ECM sends fuel to match the TB position. That's how it is supposed to work, but the question is is it working that way?

So we are way down into the weeds on this and I think it is likely one of your original steps was a mis-step with a bad part replacing a good part, but which one or two or three?
 

Uncle Gump

Moderator
Forum Moderator
Joined
Mar 4, 2020
Messages
539
Reaction score
205
Points
43
Location
Ottawa IL
Vehicle Year
1986
Vehicle
Bronco II
Suspension Style
4wd
Did you ever drop the exhaust and drive it?
 

custombolt

Member
Joined
Jan 29, 2022
Messages
45
Reaction score
14
Points
8
Vehicle Year
1989
Vehicle
Bronco II XLT
Check the distributor clamp bolt to make sure it is tight. Next is to warm the engine up & check the timing at a 750-ish rpm idle. You need about 18 degrees BTDC with the SPOUT PLUG in place which will result in about 10 degrees BTDC with the spout removed (final accurate setting). That clamp bolt can loosen up over time. Mine did at 97,000 miles. The difference in power will brighten your week.
 

Bronco 2 man

Active member
Joined
May 31, 2022
Messages
152
Reaction score
32
Points
28
Location
Boiling springs lakes nc
Vehicle Year
85
Vehicle
Bronco 2
Suspension Style
4wd
Not to familiar with the 2.9, but kinda sounds like a timing issue. Curious if auto or manual transmission?
 

LeBronCo

Member
Joined
Jan 10, 2021
Messages
156
Reaction score
19
Points
18
Location
North County San Diego
Vehicle Year
1987 and 1986
Vehicle
Ford Bronco II
Suspension Style
4wd
My credo
Life is more fun if you own a Ford Bronco II
B2 man it's a manual. No Unc, I haven't dropped the exhaust yet. But I did find a guy locally who has all the diagnostic equipment and experience with the 2.9. I'm on the calendar for 6/16. Once he gets things figured out, I post the results.
 

Top