O2 sensor question...I'm stumped!

[slimm]

I just put long tube headers on my '96 Z28 and sent the PCM to delete the rear O2's along with EGR. I got the PCM about 2 weeks ago and installed it, running the Bosch O2 front sensors. The car was feeling really heavy with no power, so I decided to buy new A/C Delco O2 sensors and installed them over the weekend.

I drove the car all day yesterady (Sunday) with no problem, the car was running smooth with a lot of power. Now the SES light came on this morning, and the codes that are coming up are P0133 and P0153 (both sensors). Any ideas what this could be? I drove the car with the Bosch O2's with no SES light, but now this! I took the car to the muffler shop today to confirm that they were plugged up (and not disconnected) but there seemed to be nothing wrong. The car is running cool, and the O2 sensors I took off this weekend don't smell like antifreeze, so don't think I have a leak that could mess up the sensors.

Do I have bad sensors? Bad extensions? WTF????????

[FANTA-Z]

If your headers were coated it is a known fact that the coating will kill O2 sensors within the first 2 weeks.

[slimm]

I've actually had these headers for over 2 months now. I replaced the initial O2 sensors with Bosch sensors. I just got the PCM tuned 2 wks ago. I'm hoping that 2 months was more than enough time to clear up the coating.

[slimm]

Actually had the headers since March, so about 5 months.

[FANTA-Z]

Yeah that should be plenty of time for the headers to have burnt off.

[slimm]

Anything else I should be looking at?

You think the O2's could be bad? It's certainly a possibility, but they are brand new sealed in the box from the dealership. This car is starting to piss me off.

[FANTA-Z]

Yeah they def can be bad but sounds like something else might be going on if they keep going bad.

[Spartan7]

Look for an exhaust leak first. Then hook up a scanner and make sure the O2's are reading voltage correctly.

[Mikes 1994 Z28]

Sorry to high jack this thread but if you have the rear o2's deleted from the PCM do you have to leave the o2's plugged into the harness or can you simply remove them and leave the connector open.

[slimm]

You can remove them. I just had mine programmed out of the computer so I'm gonna' sell the 02 simulators.

[slimm]

Now back to my question...does anybody know what could be wrong?

I took it to muffler shop today and they couldn't find a leak.

[Randy L]

Slimm,
P0133 & P0153 indicate the O2's are experiencing SLOW RESPONSE. Ever since I installed my LT headers, ORY pipe and 3" Catback, I've been getting these codes. It doesn't affect my driveability or engine power at all, as far as I can tell. I am guessing that it's due to the fact that the exhaust is now flowing much faster past the O2's and it's not allowing them to read the the mixture fast enough. I have a code reader and simply delete them every now and then.

Does anyone else experience this?

[Spartan7]

Ok, I checked my factory manuals, and it says that when both those codes are set at the same time, it's a good indication of fuel contamination. It could be from the wrong type of RTV used, oil/coolant contamination, or even if you filled up with leaded fuel.

Either way, you are going to have to replace the O2s again. I would drain the tank and purge the lines first. Then change out the fuel filter, and fill up with some good gas.

Originally Posted by Randy L

Ever since I installed my LT headers, ORY pipe and 3" Catback, I've been getting these codes. It doesn't affect my driveability or engine power at all, as far as I can tell. I am guessing that it's due to the fact that the exhaust is now flowing much faster past the O2's and it's not allowing them to read the the mixture fast enough.

And no, it's probably because you're stuck in open loop. It will run like on cold start-up, just rich all the time.

[slimm]

Originally Posted by Spartan7

Ok, I checked my factory manuals, and it says that when both those codes are set at the same time, it's a good indication of fuel contamination. It could be from the wrong type of RTV used, oil/coolant contamination, or even if you filled up with leaded fuel.

Either way, you are going to have to replace the O2s again. I would drain the tank and purge the lines first. Then change out the fuel filter, and fill up with some good gas.



And no, it's probably because you're stuck in open loop. It will run like on cold start-up, just rich all the time.

Thanks for the info guys.

The thing is the SES light wasn't on when I was running the BOSCH sensors. I changed out the sensors again (back to the BOSCH) and reset the codes and drove it half-day yesterday and all day today and the SES light hasn't come on. It seems it only came on with the new A/C DELCO sensors. I thought these were much better for the car than the BOSCH from Autozone.

[slimm]

And yes, the car is running a bit "sluggish" still. I just can't figure it out.