My 1991 305 TPI has started to act weird. This is a 50k mile car.

When the car is cold, it runs like a scaled dog.

Within about 5 minutes, after it is warm, I drop the pedal and it falls on its face.

When this happens, I can almost watch the gas gage go down.

Furthermore, when I let off the gas, the car has started to backfire like it is sending raw gas through the exhaust.

And I discovered that my gas tank is under a lot of pressure, such that one day I could barely release the gas cap, and when I did, I hissed and released pressure and vapors for almost half an hour.

Today, when this started to happen, I pulled it into my garage, raised the hood, and could hear some type of bubbling in the emissions canister in the engine bay up front on the passenger side.

Last year I replaced the plugs and fuel filter. Last week I pulled one plug to check the status and found it pretty dirty like getting too much fuel. So I replaced the air idle solenoid. Still does the same thing.

Not throwing any codes and no check engine light.

Anyone had this problem before or know what is going on?

Thanks.

 

I noticed for a while my old TPI 305 ran somewhat rich, and always had quite a lot of pressure built up in the tank, but never had any run ability issues with it though... Maybe a bad 02 sensor?