Terry Burger

iTrader: (4)

My car is running rough and missing (won't idle without 1/4 gas). It used to run fine, so I think the PCM progam is OK.

I connected autotap and all the sensors looked ok (swapped the O2 sensors
just to be safe). I also swapped the plugs, and noticed they all had a lot of carbon on them (as if the car was running consitantly too rich). For kicks I put a MAFT on the car and leaned it way out, but it didn't solve the problem. I'm wondering if its possible my crank or cam position sensors are bad? How would I verify that using autotap?

Also, how can I test the coils?


Thanks,
Terry

patSS/00

iTrader: (6)

A maft won't really affect the a/f for part-throttle, it will just cause the fuel trims to change. Maybe air is getting into the exhaust (AIR valves/pipes?) causing the o2 sensors to read too lean?

Team ZR-1

If the sensors were bad or out of sync there would be DTC error codes, so would there be error codes for ill running engine so what codes were there ?
if none, maybe someone turned off codes for them such as misfires via a tune.
If there were coil problems again then there should be misfire codes for the cylinders having the problems.

jimmyblue

iTrader: (11)

I would definitely pull codes first and then go log current
misfires looking for single-cylinder vs all-cylinder problems.
That will kind of tell you where to go next (plugs/wires/
injectors/coils vs "global" sensors etc.

Terry Burger

iTrader: (4)

The PCM has all codes disabled, unfortunatly. Can you ohm out the coils like in other cars? When I pulled the plugs, they all had a heavy black soot (and none were wet), so I suspect its running rich. In autotap there was a "air fuel ratio" readout, that was holding a steady 11.5:1 - 12:1 at idle (rich, but enough to make it run really poorly??)

Like I said I tried the maft, and also swapped mafs just for kicks, with no effect.

jimmyblue

iTrader: (11)

Measuring the resistance would only show you certain
classes of failure; I would be more worried about the
insulation breaking down, than burning wires open. The
insulation you would not see, necessarily, with a low
voltage ohmmeter.

If the commanded AFR at idle is that low then something
is pretty funny. You might check for abnormal ECT and IAT
readings, maybe it "thinks" it is still in cold start? Pull &
reseat the temperature sender connector (or see if chunks
come off along with the connector)? Not sure about ATAP,
whether this air fuel ratio is the commanded or some attempt
to guess by O2 voltage (but believe it is the commanded).
There should be a Fuel Air Multiplier PID which is the flip side
of the commanded AFR and this should be 1.0 for warm idle.
If it isn't then I would suspect some temp sensor malfunction
that prevents the car from entering closed loop and jacks the
mixture around. Don't know of any other mixture-bending
sensors but I suppose there might be some.