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  #1  
Old 12-02-2010, 08:45 PM
mossyoakranger99
 
Join Date: Nov 2010
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Default runs good cold and on idle but bad when its warm

i have a 87 ranger 2.9 that i have done alot of work too. after all my work i still dont have it running 100 percent. when the engine is cold it runs fine, it idles fine all the time but as soon as the engine warms up it starts surging and running rough until you give it wide open throttle or idle... any insight for me... i am getting tired of chasing dead ends with this old ass computer system...thanks
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  #2  
Old 12-05-2010, 07:18 PM
Psycho Pete
 
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Default Re: runs good cold and on idle but bad when its warm

Pull trouble codes from the computer to see if it can get you a hint as to what the problem may be. I would suspect ECT or o2 sensor, but would definitely run a KOER test when the engine was warm.
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  #3  
Old 12-06-2010, 10:59 AM
mossyoakranger99
 
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Default Re: runs good cold and on idle but bad when its warm

ya i put an o2 in it cause it was bad... the last things i am leaning towards is the computer or ignition control module
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Old 12-07-2010, 06:35 AM
Psycho Pete
 
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Default Re: runs good cold and on idle but bad when its warm

Run a KOER test for sure before replacing anything.

I know it's going to take a lot of patience, but read thru this: http://www.corral.net/tech/maintenance/eecivtest.html
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  #5  
Old 12-07-2010, 07:27 AM
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Default Re: runs good cold and on idle but bad when its warm

On a cold engine, the systems is running in "open loop" mode, which means most of the emissions control system sensors are being ignored by the computers. It us using preset values for everything. Once a certain temperature is reached, it goes into closed loop and begins using all its sensors to manage fuel and spark. So if it runs find without sensors but runs like crap with the sensors, I would bank on a sensor problem. Also, since it runs properly at idle, you can rule out of most of the usual culprits like IAC, TB, and MAF. Those things cause problems at idle.
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  #6  
Old 12-07-2010, 07:03 PM
mossyoakranger99
 
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Default Re: runs good cold and on idle but bad when its warm

that makes sense... how about the fact that after it gets warm and starts its problem i can shut the engine off while going down the road and start it back up the problem will go away for a few minutes or longer at times then go back to running like crap... what is resetting turning the engine on and off real quick?
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  #7  
Old 12-07-2010, 07:31 PM
Psycho Pete
 
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Default Re: runs good cold and on idle but bad when its warm

I don't know for sure what sensor is causing the issue, but a KOER test when engine is warm and checking stored memory codes will probably yield a hint.
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1987 Ford Ranger Short Bed 5.0L/T-5 Project
1988 Ford Ranger Long Bed Parts Truck
1993 Ford Tempo 2.3L OHV HSC Auto - D/D Stock.
1999 Honda Accord VTEC Auto
2002 Dodge Caravan - 3.3L Auto

Last edited by Psychopete; 12-07-2010 at 09:13 PM.
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  #8  
Old 08-11-2011, 06:28 PM
Liking the Ford Ranger Forum
 
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Default Re: runs good cold and on idle but bad when its warm

Tony. Take a look at my post 1986 missing and bucking--solved???
It might be worn throttle cable links, this causes the throttle plate to wiggle with the engine vacuum and the TPS sends bad signals to the PCM(computer).

Good luck.

gil
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