I recently had a set of Edelbrock TES headers, NGK TR55 plugs and a new O2 sensor installed on my 95 Z28. Now the car is running rich (I can tell by fuel economy gone way down and smell). HOw can I tell what is causing this? Best to bring it to a GM dealer and have them scan it? Thanx.

 

2 things I can think of. What brand O2's are you using? Do you have the ability to check fuel pressure? I would check the fuel pressure particularly after the car is shut off. If it goes down in a short period of time this could mean a fuel injector is leaking and causing the rich condition.

Also check the vac line to the fuel pressure regulator and see if it's wet. If it is wet, replace the frp, it's leaking fuel into the vac line and ultimately into the intake.

 

Is it tuned?????????

 

I dont see anything in his sig that would require pcm tuning. I agree with checking the fuel pressure and fuel reg(both easy to do). Also as was mentioned....if you didnt use the GM O2 sensors you could run into some problems....seems to be hit and miss with othe brands. Also make sure you have no exhaust leaks which would allow the O2s to see extra air in the exhaust system and cause the pcm to dump more fuel.