I have a problem with my car running very rich in open loop mode, it smells like raw fuel. There is a lot of hesitation (definitely due to misfiring as a result of fouling plugs), but after 1-3 minuts of running, when it switches to close loop everything clears, it runs smooth from idle to redline, a little rich though. My A/F ratio gauge in open loop shows almost right voltage oscillations, in close loop it shows lean. It wasn't running that rich before on exactly same tune. Something is not right. It's amazing, but it runs better in rain. New TPS, O2's, MAP. I know, that it can be a lot of things, but please, let me know what do you think about it, I am out of ideas. Thank you!

Car is '97, lt4, shorties (no leak sounds), OBDII. EGR and AIR still in place.

 

Amazing? They all run better in the rain.

 

The "cold start" A/F ratio is highly dependant on the coolant temp sensor reading. Check the coolant temp sensor readings with a scanner to make sure they make sense. I've seen black smoke pour out of a car with a faulty CTS.

Your comment about the "oscillations" in open loop is puzzling. It should start cold at 450mV, and then gradually drop to 00X mV's, indicating the sensors are heated up and reading the air from the AIR pump. Shouldn't "oscillate".

 

Thank you, Injuneer. I'll check CTS, it's probably degrading somehow. A/F ratio meter in open loop stays almost steady, I am not sure what causes slight oscillations. O2's probably are not going to provide correct readings anymore, they should be ruined from rich mixture, and it will be a good idea to replace them together with plugs.