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Idle Problem


Twister

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So i have an 87 bronco ii, i replaced the heads about 2 months ago, it runs ok but has a weird idle problem. It will idle fine for the first 5 minutes, then bog down. After driving it some, when i come to a stop, the rpms go up, then drop, then go up then drop. It will eventually try to even itself out, but that only lasts about 5 minutes then its back to the up and down.

Another problem, which might relate to the idle problem, when i first start to go after starting the truck from cold, it will cut out and if i don't let off the gas it will die. It does it once or twice then goes away when it gets a bit warmed up.

Here is a vid of the problem (sorry for the quality, recorded it on my phone)

 


Twister

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Anyone? I cleaned the IAC, the truck shuts off when i unplug it, same with the map, so i believe they are working. I am going to test the fuel pressure tomorrow and maybe change the fuel filter.
 

shane96ranger

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Have you checked for vacuum leaks?

Sent while I should be doing something else
 

jkufen

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I have the same issue with mine. I am curious to know what the issue is so I can get mine fixed also. Someone told me it might be a plug fouling out but I havent isolated the issue yet.
 

Twister

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Have you checked for vacuum leaks?

Sent while I should be doing something else
How would i go about doing that?

Also got a new symptom today, don't know if it relates to the idle problem though. I was cruising at about 40-45, and the truck would loose some power and start making a soft and fast sputtering, the truck would almost die if i gave it more gas. I had to slow down and then re-accelerate to get it to stop. It did it twice within 15 minutes.:dunno:

Could this be a fuel pump issue, when i bought the truck the fuel pump was extremely loud, it gave out a loud humming noise. Lately it hasn't been making as much noise on start up like it use to.
 

armadillon

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Spray some type of combustible around the intake in bursts. Starter fluid works well. The idle will increase because the combustible will be sucked down into the intake. You can narrow it down by getting closer and closer to the leak.

I would try the vacuum rather than bothering with the fuel pump. Honestly if you were having pump issues it would probably occur at highway and other speeds, probably not just idle.
 

armadillon

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On my 89 5.0 Moosebox the fuel pump was incredibly loud. It was kinda nice, I always knew when it was working ;)
 

Twister

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Ill try that when i get home and will report back :icon_thumby:
 

Brownie Mobile

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ive noticed that the starter fluid spraying method doesnt work all the time, get a cigar and blow the smoke through your system watch where it comes out.
 

Twister

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Well i didn't find any leaks using the starter fluid method.

I also pulled the codes

I got

11 - System checks ok
22 (maybe) - MAP (vacuum) or BARO signal out of range
32 - EVP - (R) EGR not responding properly during test - EVP

EVR - (O, R, M) EVP signal is/was low - EVR

PFE - (R, M) PFE shows low pressure, EGR not seating or memory, not seating intermittently - PFE

63 - Throttle Position Sensor (TPS) signal too low TPS
 

armadillon

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Brownie, that's a new one! Also seems a hell of a lot more satisfying ;) Twister, I unfortunately don't know enough about code-deciphering to help you as well as I should. There's a few guys here who are masters. If I had to make an edumacated guess, sounds like EGR valve. Usually not a pain to replace.

Please, someone chime in and make me look smart. I know it's difficult.
 

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