1994 Mercury Tracer



February, 11, 2007 AT 9:25 PM

118,000 miles.

When the car is in park or neutral the idle on my 1994 tracer lopes from about 500 rpm to 1200 rpm. If the car is in drive or reverse, the car idles a little rough at about 1000 rpm but it does not lope. It only lopes without a load.

The car was tuned up before I bought it and we checked and gapped the platinum plugs (0.054). Wires are ok.

I changed all loose and damaged vacuum hoses (most hoses were leaking or brittle), new pcv valve and installed a new temp sender for the temp guage. The ECT was not changed.

The EGR valve and EGR vacuum circuit passed all tests.

I have a Scantrol with a Ford cartridge. The KOEO tests (fast and slow) came back ok, ie. Returned a 111 code. The systems monitored while the car is running are within specs, ECT, EGR, IAC. MAP, O2.

I get a 412 and 411 code when I run a KOER fast and slow test. I got the sensor test specs from a Mitchel manual and the Idle air control solenoid passed all non-pcm related voltage, resistance and short tests. I was looking for the 60 pin connector for the PCM, but I am afraid it is behind the instrument cluster. I did not get to the throttle position sensor.

Is the 60 pin cable for the pcm behind the instrument cluster? My basic problem is where to go from here? One other note, I can stop the loping by holding down on the pedal slightly. I can put just a light amount of pressure on the accelerator to boost the idle up to about 850rpm and the loping will stop. Seems like the TPS is a problem, but would it give a IAC fault? What circuit causes the rpm to increase in drive that would override the TPS at idle?


Egr Valve


5 Answers



February, 12, 2007 AT 7:48 AM

Predetermined load in the PCm sets the in gear idle, like when you turn on the A/C, the PCM knows what is necessary to keep the engine from stalling.I would lean more toward the IAC system just because it is an idle only problem. TPS could have a bad spot in it, but more likely the IAC is having a problem



February, 12, 2007 AT 10:34 AM

Since the rpm's are coming up on a load, ie in drive, and the iac tests ok as far as resistance and no shorts is it more than likely a problem with the IAC plunger or the IAC to PCM communications? Any way to test the plunger operation in the IAC?

I should be getting a breakout box this week off fleabay. Will work on my truck, so the 20-30 bucks should be worth it, so I will test the PCM to IAC.

The voltages varied on the TP when I monitored the datastream, so I don't think it is the problem. The idle would smooth out as more air entered as the throttle opened.

Where is the 60 pin connector on this car? Can't find a reference to the location anywhere.



February, 12, 2007 AT 4:11 PM

Wouldnt be the first time a part tested ok, but wasnt



February, 25, 2007 AT 11:06 AM

Be sure to check and make sure that you dont have a vacum leak. Ran into this several times before when I wasted time changing a good iac



February, 26, 2007 AT 7:08 AM

You need to clean the butterfly valve in your throttle body to be sure this isn't causing a problem.

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