My car is running rich. I have installed pacesetter LT headers with 2.5 custom x pipe with TR55 plugs and JEGS 8.5mm wires. I have a mail order tune for all of my mods from PCMforless and this problem just started with in the last couple weeks. I have no codes and the O2 sensors are still the same ones I had with the stock exhaust(probably not a good idea) but at the time I didn't have the money for new ones. It is rich enough to burn your eyes when it idiling.

Here are my questions.

1. Why would cause my rich problem if the tune supports my mods?

2. Why would it not throw any codes?

 

Obd 1 doesn't throw codes for just everything like an Obd 2 car will. The best thing to do is get a scanner hooked up to it to monitor o2 switching and all other sensors.

 

If the headers are coated it might have ruined the O2's.

 

Anything that screws up the O2 sensor readings can cause it to run rich:
-misfires
-exhaust leaks before the O2 sensors
-sensors contaminated either internally or externally
-faulty harness extensions

Doesn't really have much to do with the "tune", since the PCM is hard coded to produce a 14.7:1 A/F ratio in closed loop. If its not producing those results, there a good chance the feedback from the O2 sensor is throwing it off.

 

I have ran the car with a scanner on it with the sensors showing that they were working good. Also the headers are not coated. I am starting to think I may have bad injector. As soon as i get a chance I need to check the injectors to see if one is sticking open. Good ole trial and error.

 

How can you tell by looking at a data log that the O2 sensors are "working good"? If the O2 sensor voltage is actually lower that its supposed to be for a given O2 content, the PCM will add fuel to that bank of the engine, until the O2 sensor voltage returns to where it should be. It will look "good", but it will be running rich. A faulty extension could be throwing the voltage off. Since you have a scanner, what do the long term fuel corrections looks like at idle (Cell 16)?

If you have a leaky injector, the fuel pressure will drop rapidly when you shut the engine off. Have you checked that?

 

Lesson learned thanks Injuneer....I don't have a scanner but have access to one. Is there an O2 sensor extension for when i buy a set of AcDelco O2 sensors due to the LT headers?

 

I used a stethoscope to listen to the injectors so I was able to confirm they were working. Not sure if you had one sticking that the sound would be different but at least if one stopped working it would sound different.

 

Could transmission fluid spilling over the header and 02 contaminate the sensor?
The cooler lines connect to the tranny immediately above the O2 on my LTs.

 

Yes. I had a sensor destroyed by leaking power steering fluid on my wife's Grand Cherokee.

 

Did you ever resolve the issue?
Was it occurring only once the car was in closed loop or all the time?

 

Yes i did. I put new O2s and new extensions on the car and it cleaned it up alot