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Bogging down at 3k rpm


vonD1025

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Hello,
So I’ve got a 1987 Eddie Bauer Bronco ii with a 88” 2.9l engine and swapped a manual transmission into it with the 4:10 gear ratio on there. I’m having issues bogging down a little bit every time I hit 3,000 rpm. I’ve been hesitant to take it on the highway since last time I lost all power.

Figured out it was something to do with my wiring coming loose on the control board. Since then I’ve replaced the air filter which I found a hole on the housing and threw some jb weld on to fix. Also replaced the Throttle position sensor and the fuel pump wasn’t done to long ago. As well I replaced the water pump. I’ve seen two leaks I know these are notorious for having and that’s the gaskets for the valve covers and the timing cover. Not sure if that would have anything to do with it.

Looking forward to getting this old girl up and running 100% and hopefully off road ready soon. Thanks for any feedback!

Nick v.
 

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dave84b2

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My dad had a 88 and we changed both fuel pumps, one in the tank and the other one is under the drivers door on the frame rail it is a canister with filter in it, it is the secondary pump, might want to check that..
 

vonD1025

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So yeah little update. I went out to start it up and start checking things out. It barely cranked up and ran like crap for a sec then died. If I try to turn it over now it seems like it’s getting no fuel(I assume) ..
 

LeBronCo

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Hello,
So I’ve got a 1987 Eddie Bauer Bronco ii with a 88” 2.9l engine and swapped a manual transmission into it with the 4:10 gear ratio on there. I’m having issues bogging down a little bit every time I hit 3,000 rpm. I’ve been hesitant to take it on the highway since last time I lost all power.

Figured out it was something to do with my wiring coming loose on the control board. Since then I’ve replaced the air filter which I found a hole on the housing and threw some jb weld on to fix. Also replaced the Throttle position sensor and the fuel pump wasn’t done to long ago. As well I replaced the water pump. I’ve seen two leaks I know these are notorious for having and that’s the gaskets for the valve covers and the timing cover. Not sure if that would have anything to do with it.

Looking forward to getting this old girl up and running 100% and hopefully off road ready soon. Thanks for any feedback!

Nick v.
Nick,
It sounds like a vacuum leak somewhere on the intake chain
 

JerryC

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So yeah little update. I went out to start it up and start checking things out. It barely cranked up and ran like crap for a sec then died. If I try to turn it over now it seems like it’s getting no fuel(I assume) ..
Check the fuel pressure with a gauge, don't assume. There is a test point on the fuel rail, driver side.
Do you hear the pumps run when you turn the key to "on"? They only come on for a couple of seconds.
Have you checked for spark?
 

vonD1025

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I replaced both pumps and it worked for a bit but then burnt out the high pressure pump. I figured out there are two fuel filters as well as pumps so I’m changing the filter I missed. Getting no pressure to the release valve.

Curious if anyone knows if the fuel pump is wired correctly?
 

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vonD1025

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Nick,
It sounds like a vacuum leak somewhere on the intake chain
I did have a huge whole in my air intake box that I had to epoxy back together. Then I ran into the fuel pump issues.
 

vonD1025

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Ok so after replacing the low pressure/sending unit, fuel reservoir, high pressure fuel pump, and fuel filter plus I dove in and did the spark plugs (gapping them at .044) it ran for about an hour. I parked it and took a shower real quick. Went back out to start it and the engine sputtered and died. It’s acting like it’s getting no fuel again or at least I think so.

I’m about at the end of my mechanical limits. Any help would be appreciated?!? Can’t wait to just go 4 wheelin guys haha. It will be worth it!
 

dave84b2

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4wd
I would check the fuel regulator, use something to depress the shrader valve on the fuel rail to see if there is fuel coming out be careful it may spray, you could also use a fuel pressure gauge and see what the pressure is, if all that is good then i would check the TFI module on the distributor, they have a tendency to go bad due to heat from the engine when it has no body lift, best investment is a chilton manual for the bronco ll especially for all the electronics on them..
 

dave84b2

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stock 2.8.. 231,257 miles still going strong!! rebuilt 2.8 bored .040 has 5,000 miles now 11/14/20
Suspension Style
4wd
One more to check the IAC valve, it is a idle control valve if this is working correctly it will on start up speed the engine up on first start then the engine once warm it will idle back down, it took the replace of the old choke caps on older models, but does the same thing.. also a carboned up egr will cause it to run ruff and hard start or no start, these are all symptoms of my dads old 1988 2.9 i had to mess with.. note your fuel pump inertia switch is located on passenger side normally under carpet pad at the beginning of it up under dash.. hope this helps you out
 

McWillies

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Sounds weird but try starting it again and keep it from stalling out with the gas pedal and see if the idle goes back to normal. If it just dies out then I'm probably wrong but if the idle clears up you might have coolant getting in a cylinder or two... or three. Also if all this has been on the same tank, might be bad gas.
 

JerryC

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I ended up burning out the high pressure fuel pump because of a bad inertia switch. Ended up jumping it with a wire.
How did it do that?
 

vonD1025

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It kept trying to pull gas to the high pressure when the inertia switch wasn’t letting it pull from the lower. Idk it squealed loud and yeah didn’t work after about an hour. So I replaced it and jumped that switch and it works perfect now
 

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