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Duratec Surging Idle

G

greasemonkey1489

Hard-core CEG'er
Joined
Apr 14, 2008
Messages
1,568
Location
Bloomington/Normal, IL
I recently put a used motor in my 1995 Contour SE 2.5L. The main wiring harness was frayed and I was able to find a brand new one on ebay. I have the MTX-75 tranny however the liquidator failed to mention that the harness was for an automatic. I studied wiring schematics and decided that the harness should work fine. I was able to splice in a park neutral safety switch for the MTX. The engine starts and runs but it surges at idle. If the idle steadies, it idles around 2500rpms. Then it will surge and gradually increase in idle speed - nearing 3500. I hooked up diagnostic equipment and it gave codes for the MAF, TPS, IAT sensor, and the Water temp sensor. The exhaust smells very lean too. Has anyone had any issues like this? The only sensor on the new harness is the MAF and the pins to the ECU match on both auto and MTX harnesses
 
My 95 SE had a hanging idle and at times would even increase when the clutch was disengaged.
However, that was only when driven.
In park it idled fine and when reved it always returned to idle.
It may be the egr valve or idle air valve.
They may need to be cleaned.
Or it may be in the wiring, computer wise.
I saw the harness on Ebay and asked him to verify atx or mtx.
He did note atx when he relisted.
I also called my buddy at Ford to verify the application.
He said it would not be wise to modify a atx for use in a mtx.
Too many issues.
Good luck.
 
My UIM has been completely cleaned out and the EGR has been tested, so I don't beleive that it could be an issue. If I unplug the IAC valve while the car is idling, there is no change. I've checked for vacuum leaks and still have found nothing. I might just go strip a 96 se harness from the bone yard for kicks. Does anyone have any other suggestions?
 
I tested the IAC and it tested within spec. I found that the IAC harness wire was shorted and I bypassed it, tested it and it is not shorted anymore. I ran the engine, it did not surge but held a steady idle at 3000rpms. Has anyone with a bad alternator had the idle increase on its own? The battery light stays on on the dash and when I test accross the battery terminals, it reads only 12v after the battery has been on a trickle charge but shouldn't it read closer to 14v when the engine is running?
 
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