4.0 hi idle
Thread Starter
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Cargo Master
Joined: Feb 2002
Posts: 2,414
Likes: 22
From: Tucson USA
4.0 hi idle
No not the regular type like from a bad IAC. I recently pulled the plenum and had the injectors checked and cleaned. Put all back together and when cold idles as it used to, but when woarm will develope a high idle by about 4-500rpm. I suspected a vacumm leak but it would idle down for one of those right?
Cant be bad IAC as mine is disconnected. I cleaned the plenum and the TB while I had it apart so all should be good there. Just wondering if the MAF needs to be checked, I R&Rd several years ago. Thoughts on this.
I have not tried any codes, milage has not really changed but it is aggrevating to now how this situation.
94 4.0 2wd SC.
Thanks Hank
Cant be bad IAC as mine is disconnected. I cleaned the plenum and the TB while I had it apart so all should be good there. Just wondering if the MAF needs to be checked, I R&Rd several years ago. Thoughts on this.
I have not tried any codes, milage has not really changed but it is aggrevating to now how this situation.
94 4.0 2wd SC.
Thanks Hank
Moderator
Joined: Jan 2004
Posts: 13,851
Likes: 111
From: SW Va
Yup, scan the computer for trouble codes & post ALL the code numbers found.
WHY, do you have the IAC disconnected??? This will confuse the computer on what to do about idle speed.
You might check the PCV valve & it's hoses & connections, if it hasn't been serviced lately.
With it changing after warming up, it sure sounds like a gasket problem, was it there before the UIM was removed for the injector work???
Did you remove the B- battery cable before the manafold/injector work, to wipe the computers memory????
If not, you need to, as the computer will be confused, as it needs to relearn it's cold & warm idle strategy with the IAC connected & to begin to build new fuel trim tables after the repair, otherwise it'll be trying to run the engine on the old fuel trim tables it has learned before the repair work.
Any mods to the air intake, or other engine mods, or items disconnected???
A bunch to thoughts for pondering. Let us know how it goes.
WHY, do you have the IAC disconnected??? This will confuse the computer on what to do about idle speed.
You might check the PCV valve & it's hoses & connections, if it hasn't been serviced lately.
With it changing after warming up, it sure sounds like a gasket problem, was it there before the UIM was removed for the injector work???
Did you remove the B- battery cable before the manafold/injector work, to wipe the computers memory????
If not, you need to, as the computer will be confused, as it needs to relearn it's cold & warm idle strategy with the IAC connected & to begin to build new fuel trim tables after the repair, otherwise it'll be trying to run the engine on the old fuel trim tables it has learned before the repair work.
Any mods to the air intake, or other engine mods, or items disconnected???
A bunch to thoughts for pondering. Let us know how it goes.
Thread Starter
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Cargo Master
Joined: Feb 2002
Posts: 2,414
Likes: 22
From: Tucson USA
pawpaw, new pcv valve, yes on the battery, there is a short in the wiring harness someplace for the IAC, it has been disconnected for several years, has a free flow air filter, been there for several years also.
This is a new problem, because it only does it after its warm is the confuser. Its obd 1 so I need to take it in but all the stores have gotten rid of their obd 1 code takers!
This is a new problem, because it only does it after its warm is the confuser. Its obd 1 so I need to take it in but all the stores have gotten rid of their obd 1 code takers!
Moderator
Joined: Jan 2004
Posts: 13,851
Likes: 111
From: SW Va
Good find, fix & feedback on the PCV hose.
Now take the time to continue on & fix the IAC wiring problem to get it back online to help the computer properly control idle speed on those cold starts & to properly idle up the engine when the AC kicks on.
BTW, if your using a oiled foam, or cotton gauze air filter, you'll need to keep an eye on the MAF cleanliness & if dirty & it's PID to the computer is corrupt, pull & clean it with a plastic safe non residual cleaner, like CRC MAF Sensor Spray Cleaner.
Now take the time to continue on & fix the IAC wiring problem to get it back online to help the computer properly control idle speed on those cold starts & to properly idle up the engine when the AC kicks on.
BTW, if your using a oiled foam, or cotton gauze air filter, you'll need to keep an eye on the MAF cleanliness & if dirty & it's PID to the computer is corrupt, pull & clean it with a plastic safe non residual cleaner, like CRC MAF Sensor Spray Cleaner.
