I'm on my 3rd O2 sensor on the left bank. Every couple of months I get a horrible idle and check engine light w/ a code 44 (lean). When I pulled the sensors they are completely fouled out. Covered in soot. I was wondering if you all had any ideas it could be??

I'm thinking maybe I have a leaky injector that is causing the sensor to get covered in soot, which causes it to read leaner and leaner over time to the point where it is over the acceptable limit.

I've datalogged the problem and it seems to be at low RPMs mainly idle. Accelerating the numbers for the O2 are all right but at idle when in closed loop they are way off.

Today I’m going to check the injectors and see how they look. I just wanted to see if you all had any other suggestions.
Thanks
Jeff

 

What do your BLM's read? If the left bank is living well above 128, I'd take a look at the injectors. How many miles on them?

 

Any chance that you have an exhaust leak on that side where the problem arises? Leaking fuel injectors typically would not cause this problem.

 

How about coolant contamination. That will kill an o2 sensor quickly. A leaky injector would be reflected in your fuel trims and set a rich code long before it got to the point of fuel fouling the sensor.

 

Thats possible but he would be losing coolant then. Also the sensors are covered in soot because, before the PCM goes in to back up mode, the PCM actually will attempt to correct for the lean condition by adding fuel when the engine isn't actually lean. This causes a rich condition which compounds itself if the PCM continues to correct for a lean condition that doesn't exist. This happens more than one may think, many times o2 sensors get asphyxiated. By this I mean that uknown to a lot of people o2 sensors needs a reference air sample to send a correct signal to the PCM. For it to do this it "breathes" through its wiring using the insulation as a breathing tube. Foul or plug this off and the sensor will report a lean condition. I have seen o2 voltage levels drop to .100mV causing the PCM to peg its correction trims and virtually fouls the plugs.

 

I'll bet the problem lies in a burnt harness on that side.

 

hey! not a bad idea! I noticed wisps of smoke coming from the pass. side and a burning wire smell... 2 weeks later, SES light, o2 sensor heater not working!

 

Thanks for all of the replies. I just got back from a long data logging session. Its funny the car acted up all night last night and then I tried to datalog it today and it drove fine for an hour before the problem started. After warming up the car develops a miss (not sure how else to describe it) at all RPMs but at idle it is really bad. The car shakes and sounds like it is going to die. It never died on me though. The O2 sensor on the left side starts reading a relatively constant number that steadily goes down. In other words the O2 stops fluctuating when the car starts acting funny. I'd be happy to send anyone the .uni file to take it look at if it would help.

If it was coolant contamination wouldn't it show up in the oil and wouldn't it kill the O2 permanently and not function at all. The car usually runs good till it's warmed up. Also wouldn't a burnt wiring harness be a permanent situation too??? Any suggestions???
Thanks

 

I pulled the injectors and they looked very good. I cleaned them with some cleaner and put them back in. The car ran fine for a few hours then the same problem. Would the coolant contamination show up in the oil???

 

Using any silicone sealant or spray any silicone any where? Silicone will kill O2 sensors quick.

 

At idle I would check the coil ,find a dark grage and check the sides of the coil see if it is going to ground.
I would also check the wiring harness for the coil.
What is the high and low reading on the o2 sensors.
should be 800 high and 54 low,left or right.
Is the trans shifting good at WOT?

 

No I haven't used any silicon. This has been going on for several months. The coil has a very good spark. It is new. Could a EGR valve getting stuck cause this problem??? I'm at a loss.

 

That sure is a coincidence. I would check the continuity of those wires. The fact 1. you smell / see some smoke
2. you get the code (SES light)
3. you find your O2 heater isn't working.
Get your Helms out to locate the 'Pins" where you can do this without doing more damage to the wires.

 

I agree, check the wiring to the O2... soot, especially black, makes me think rich condition, not lean.

Also, your injectors may look good, but could be toast. You need to remove the injectors, and turn on the key. If one is running, or oozing, then you know the source of the problem.

If it was coolant contamination, I would expect it to be whiter. Check your plugs on that side, too. If they are all fouled, they may need to be cleaned.

 

I pulled the rail and none of the injectors leaked as far as I could tell. Since the problem lies in the left bank, I switched the injectors from the right to the left and vice versa. Still got the code 44 (left O2 lean). I know the car is not lean the left exhaust pipe is black and the bottom of the car around the left pipe is black. Something is tricking the O2 to read leaner and leaner.

This is pretty much what happens...The car will run great for a hour or so then it develops into a slight rough idle...which developes into a miss at all RPMs and a extremely bad idle (the car shakes pretty good). And some black smoke from the left pipe (black). Data master shows the O2 working fine for that hr. Its high and low voltages are about right but then out of the blue it starts reading a constant voltage of about 220mV then drops. This is causing the injectors to be turned on for way too long. Thus my rich condition. Then after 30sec. of running the O2 below 200mV, Code 44 is thrown.

I'm fairly sure it is not directly related to engine temp because it only does it when the car had been running for a while. For instance, If I start having these problems and shut the car down for a couple of minutes and start it back up it will run fine for a little while.

I check the wiring on the O2. As far as I can see visually everything is OK. Is there any test I can do to the harness?

Thanks

 

So you only have the problem when the engine goes into closed loop?

What codes have you pulled? other than the 44

Remember when the car is rich out the tail pipe, it is lean at the motor.

 

probably completely off. but i like to mention it every time someone has a rough running car. clean the terminals on the water temp sensor on the front of the waterpump. takes 10 seconds to do but i thought id mention it cuz i had a rough running car for 3 months and that was the problem !

gluck!

 

I only have the problem in closed loop and 44 is the only one the PCM throws. It's crazy after a while of driving the car the o2 just starts reading a constant 200mV then drops. I pulled the plugs and they were extremely rich on the left side and fine on the right. I don't know what could cause the O2 to run fine for a while then start screwing up. Like I said before, the wiring looks fine but is there any way I could check it?? I will check the coolant temp sensor because I've had that problem before and it was very similar. Any thing else I can check??? I'm running out of ideas fast. Thanks.

 

when i hooked my car up to the scanner at a freinds shop the temperature read -200 or somethng odd like that. how about the ecu? maybe do a quick swap with someone and see if it helps? On my old heavily modded 300zx turbo i had serious issues one year when we went with a higher boost setup. but basically the car ran bad and i swapped a new ecu and it did fix the car 100%.

 

I really don't have access to an ECU. As a last resort, I'll go to the Corvette salvage and ask if they would let me try one. I just cleaned those water temp terminals and I'm going to take it out and datalog it again. If anyone wants to take a look at the datamaster file, I'll be happy to send it.