a REAL screw up!!

[HYspd]

OK...
got a 95 Contour in today...
2.5 AT...

customer complaint..

1, sometimes it runs horrible and stalls ALOT, won't take any throttle
2, other times runs great but stalls if you step on the brake pedal
3, occasionally blows huge ugly dark gray clouds that smell unbelievably bad from the tailpipe.
4, low coolant light on for no reason

all have been verified (witnessed) by me...

i tried a Snap On MT2500 on it and the PCM acts like it's posessed..

it won't complete self tests, won;t give the same results twice if it decides to complete more than one test in any given hour..when it runs like crap, the serial data looks reasonable, except that the plugs are coal black even though it show are the O2's ARE swapping high lows fairly quickly, and it's only running on three cylinders of the six total and it switches which cylinders will run at random in a fairly rapid cycle UNTIL the brake pedal is pressed then the O2's go straightline the front at about .2V and the rear at .495V...when it runs well, serial data will fail to communicate within 30 seconds with 0 seconds being the norm.. if at anytime in a self test i press the "N" button to back out of the test it kills the engine as will pressing the brake pedal...seems to run ok"ish" with the MAF unplugged.....

any hints clues ideas hopes prayers or religous artifacts that might help?



unplug the MAF and yank out the MIL bulb?

[AltecZX2]

If the PCM wont self test, replace it Ive had them die on me. Work from there.

[Jason43]

2. Sounds like a vacuum leak around the brake booster. That could possibly be the cause of #1 as well.
4. The coolant level sensors are very picky. Add a little more coolant and it should go out.