99 Grand Prix fuel consumption

[chad austin]

My daughter has a 99 Pontiac Grand Prix with a 3.8 non-supercharged motor with 215,000 miles. Last week she called and said her car was running funny, so I drove to where she was and found the catalytic converter was shot (the short pipe between the converter and muffler was glowing). I replaced the converter and muffler but her car is still running the same (sputters at low RPM and consumes A LOT of gas). We live about 8 miles from where she works and round trip she goes through about 3 gallons of gas.

Could the Throttle Position Sensor be causing this? I was told that the TPS could be the issue?

[Macgyver55]

Did it have a check engine light on when this happened?

[chad austin]

The check engine light did come on when this happened, it is still on.

[Jeremy airjer W]

I would check for codes first.

You can check the fuel pressure regulator to see if it is leaking. You can also unplug the MAF sensor to see if the condition improves. It's unlikely that the TPS would cause this. It's more likely an air flow metering issue, really bad fuel pressure regulator, or even an injector stuck open.