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How to- 2.9 idle adjustment

rusty ol ranger

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So i had a surgeing, kinda low idle i was blaming on the charging system. I still think that might be an issue but i happen to run across this...
20200322_105519.jpg


I know the 2.9 is famous for its shitty idle, but i did this procedure and inital results are amazing. It idles about as good as my 97 460. Ill update this post as i drive it more...but wow what a difference.

Could a mod sticky or put this in the FAQ?
 


Shran

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Done. Great information, I will have to try this on my '87. I initially thought it had a vacuum leak, and it did, but fixing that and resealing everything from the lower intake up only dropped my idle RPM from 1200 to about 1000...I am sure someone has messed with it and it needs to be reset.
 

rusty ol ranger

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Done. Great information, I will have to try this on my '87. I initially thought it had a vacuum leak, and it did, but fixing that and resealing everything from the lower intake up only dropped my idle RPM from 1200 to about 1000...I am sure someone has messed with it and it needs to be reset.
I need to get a laser tach and get it real dialed in....i think it might be just a smidge high yet...but way better then it was...idled way low and loped like a drag cam. Its pry in the 800rpm range right now...but with my POS exhaust its hard to tell...it might be right on.
 

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Thats good info to keep. What type reference manual is it in? None of mine have it. I stumbled on this when i did the top end on my 87 three years back and the idle hasn't changed at all. I remember 2000 rpm for 2 minuets and it died as soon as i took my foot off the pedal, off by 2 turns in. Thanks Dirty
 

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So i had a surgeing, kinda low idle i was blaming on the charging system. I still think that might be an issue but i happen to run across this...
View attachment 68165

I know the 2.9 is famous for its shitty idle, but i did this procedure and inital results are amazing. It idles about as good as my 97 460. Ill update this post as i drive it more...but wow what a difference.

Could a mod sticky or put this in the FAQ?
I read a few threads talking about 2.9 crappy idle. Mine idles fine but she shakes like a gogo dancer. She don’t miss just shakes. Smooths out some when she warms up. I’ve been attributing it to a 30 year old motor mount. If I stick a pry bar under the mount and across the tire and sit on it the shake stops. What are you referencing when you talk about crappy idle.
 

rusty ol ranger

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A legend to the old man, a hero to the child...
I read a few threads talking about 2.9 crappy idle. Mine idles fine but she shakes like a gogo dancer. She don’t miss just shakes. Smooths out some when she warms up. I’ve been attributing it to a 30 year old motor mount. If I stick a pry bar under the mount and across the tire and sit on it the shake stops. What are you referencing when you talk about crappy idle.
Shakeing, tremoring, things like that. Ive never had a 2.9 idle what i would call smooth, really none of the early EFI fords ive had did. Once they got up into the early to mid 90s they seemed to kinda get them figured out
 

rusty ol ranger

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Thats good info to keep. What type reference manual is it in? None of mine have it. I stumbled on this when i did the top end on my 87 three years back and the idle hasn't changed at all. I remember 2000 rpm for 2 minuets and it died as soon as i took my foot off the pedal, off by 2 turns in. Thanks Dirty
Im not sure. I found it on google
 

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What type reference manual is it in?
Ford 1987 Engine/Emissions Diagnosis Shop Manual. If you have the breakout box, this shop manual is a must have.
 

Skooby

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I'm curious if this works on the later models as well? 91-92? And if so how do you reconcile for the TPS voltage being high or low after adjusting the idle this way?
 

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I'm curious if this works on the later models as well? 91-92? And if so how do you reconcile for the TPS voltage being high or low after adjusting the idle this way?
Should work on any 2.9.

You would adjust the TPS position to fix the voltage if it is out of spec. IIRC it just needs to be around 0.75-1v at closed throttle. In theory adjusting the idle speed down using this procedure would decrease the TPS voltage anyway when you dial the stop screw back.
 

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My issue is a low idle and if I use the stop screw to raise the idle it going to push the TPS voltage over 1V and mess with the computers parameters....i also found this on another site that breaks it out a bit more by the years
Screenshot_20221020-121919_Acrobat for Samsung.jpg
 

rusty ol ranger

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A legend to the old man, a hero to the child...
I
My issue is a low idle and if I use the stop screw to raise the idle it going to push the TPS voltage over 1V and mess with the computers parameters....i also found this on another site that breaks it out a bit more by the yearsView attachment 84084
I would verify that your IAC and TPS is properly functioning before attempting to manually adjust the idle.

I had a low idle on mine that was the result of me screwing with the screw before, this procedure helped me get it set properly after the IAC and TPS didnt help.
 

Shran

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My issue is a low idle and if I use the stop screw to raise the idle it going to push the TPS voltage over 1V and mess with the computers parameters....i also found this on another site that breaks it out a bit more by the years
If that is the case you might have to hog out the screw holes on the TPS so that it has more adjustment room and then turn it accordingly.

Dang, '87 2.9 is supposed to idle at 650RPM +/-... might have to mess with mine a little more... it stays around 800 after doing the original procedure in this thread.
 

Skooby

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My under hood sticker is a hundred r0m higher than this chart shows too....
If that is the case you might have to hog out the screw holes on the TPS so that it has more adjustment room and then turn it accordingly.

Dang, '87 2.9 is supposed to idle at 650RPM +/-... might have to mess with mine a little more... it stays around 800 after doing the original procedure in this thread.
 

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