Running Rich - Why?

[95 Laser GT Ver]

The motor has been throwing codes 173 & 137 (rich bank 1 & 2). Here's what I have done so far;

changed the O2 sensors
changed plugs today (plugs were black on both banks except for the very tip of the plug) but light still comes on.
run balance test on scanner, OK
swapped ECU

All of this has resulted in no change. Here's where I am now;

No long term fuel trim numbers for either side after 30 miles of driving and 15 to 20 minutes of idling
bank 2 O2 sensor only shows reaction between .86 and .95
bank 1 O2 sensor shows normal reaction .24 to .85
Cleaned MAF wire
Idle speed runs up and down constantly between 825 and 1,000 rpm
CEL can come and go. Driving for 15 minutes at various speeds, no light. Sometimes the light will come on immediately. When the light comes on, sometimes it will stay on for an extended period. Other times it can turn off within a couple minutes. I can't relate this to any type of vibration or bump in the road.

Any suggestions on where to go from here? How can I check the injectors while in the car? (But all plugs were black from soot.) Can the fuel pressure be too low? It's showing about 33lbs vacuum off. After I turn the motor off, I can watch the pressure pulse slightly as it falls to zero in about 10 minutes.
Could it be the MAF?

HELP!!!

 

[HISSIN50]

Couple lame thoughts:

I would want to ensure the O2 wiring on that one bank is ok (ohm it out if you disire). Resistance in the wiring can screw up the switching amplitude, though it usually is evenly diminished before and after stoich.

Have you ohmed out the ECT and ACT's? That can lead to a rich condition.

That FP is a little low. You should see 38-39 PSI at simulated WOT and 30-33 with the vac line attached at idle.

Good luck.

 

[mo_dingo]

The O2 sensors are telling you that the engine is running rich during closed loop operation. Obviously the O2's are doing their job b/c all of the plugs were toast.

Have you checked your cap/rotor contacts???? Spark plug wires???

THe maf/ect/iat are not your problem.

I don't know what to tell you. I don't see how the O2's would allow the engine to run rich. It should keep cutting fuel and keep cutting fuel until it's stoich.

Do you have a computer tuner that's forcing a static a/f ratio in CL? Or is the comp stock w/ no tune? Chip????

Try disconnecting the battery, reconnect later and go for a test drive (20 minutes at least). See if the MIL come back on.

The comp may be able to adjust itself if it starts from scratch; that's my guess anyway.
Scott

 

[95 Laser GT Ver]

The O2 sensors are telling you that the engine is running rich during closed loop operation. Obviously the O2's are doing their job b/c all of the plugs were toast.

Have you checked your cap/rotor contacts???? Spark plug wires???

THe maf/ect/iat are not your problem.

I don't know what to tell you. I don't see how the O2's would allow the engine to run rich. It should keep cutting fuel and keep cutting fuel until it's stoich.

Do you have a computer tuner that's forcing a static a/f ratio in CL? Or is the comp stock w/ no tune? Chip????

Try disconnecting the battery, reconnect later and go for a test drive (20 minutes at least). See if the MIL come back on.

The comp may be able to adjust itself if it starts from scratch; that's my guess anyway.
Scott

Cap, rotor, and wires are all new. The tune with an Autologic chip is looking for the normal values for the sensors.

Why aren't the long term fuel trims being established?

 

[iluv95stangs]

Maybe check and see if fuel is coming from the vaccum line on the fuel pressure regualtor. I have seen this more than once where the diapragm tears in the regulator and sucks fuel in the vaccum line into the intake causing lower fuel pressure and rich condition. Just a thought.

 

[95 Laser GT Ver]

Thanks for the idea but I checked that and it looks dry.

any other ideas? This is driving me crazy.