I bought a 91 G92 code Z28 over the weekend. There is a pretty strong gas smell coming from the car. Nothing is leaking it just smells like it's running rich. While under the car today to swap out a shaky starter motor I noticed a wire coming from the harness with a missing pigtail. It's a single wire coming from the harness above. I can't find an o2 sensor on the exhaust anywhere. (the exhuast is mostly aftermarket). I'm wondering if that wire is what used to be the connection for the o2 sensor...right near the starter where the right side of the Y pipe comes down. Does anybody know what this is? Could the lack of an o2 sensor be what is causing the gas smell from the exhaust? Why is my engine light not on? I know there is a bulb in the dash for the dummy light because it illuminates when you put the key to the on position. I'm dumbfounded.

 

Is it a single "purple" wire? If so, that's for the O2 sensor. Your car should have SES codes. Has the motor been replaced? People need as much information as you can give for a better diagnostic advice.

 

That wire is so filthy I can't tell what color it is. I'll have to try and clean it. But no, the motor has not been replaced. The car has all of it's original drive train. It's a 1991 305 TPI 5spd G92 code car (dual cats)

 

What is an "SES" code? And how do I pull them?

 

I know you said the check engine light does not come on, but it may have stored codes in it. SES (service engine soon) or some call it CES (check engine soon) https://www.thirdgen.org/service-eng...ht-error-codes I would like to suggest that you go to an auto parts store and purchase a repair manual also, they help you understand what's going on and how to find problems with your car.

 

I'm wondering if the prom chip was changed to keep it open loop? Essentially ignoring the o2 sensor or sensors? I think this 91 TPI 305 might have 2. Not sure.

 

Have you looked in the ECM to see if it has a piggyback chip in it?

 

The O2 sensor would originally be in the exhaust manifold on the driver side.

Does the car have headers now?

 

It does not have headers and there is an o2 sensor on the drives side manifold. Did these cars have 2 sensors?

 

Just one.

Is it connected?

 

The one on the drivers side manifold is connected. I'll take a picture of this mystery single wire tonight after work and share. Like I said before. It's on the passenger side and is in the vicinity of the y pipe/starter. It's coming out of the harness above and it appears as though it once had a pigtail connector of some sort on it. So it looks like a factory wire.

 

It maybe a knock sensor wire then.

 

It's a single gray wire.

 

The knock sensor is a white wire, the grey wire should be for the 2ndary cooling fan switch.

It (switch) should be below the spark plugs, and I think between #6 and #8.

PS...might be time to move your questions over to the TPI board.