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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mossyoakranger99

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.

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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mossyoakranger99

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

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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(Formerly)
FireRanger
2003 Edge 4.0 4wd

How to: Aux light wiring, relays, & fuses
Info: 300+ intake threads here on FRF
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How To: NO HEAT Troubleshooting Guide

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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mossyoakranger99

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.

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