Stock IROC, running very rich. So much so that if your standing within a 15 foot radius of the car your clothes get saturated with fumes. Can also smell it a little bit while driving with the windows down but T-tops still in place, but that might be from a slight exhaust leak, the point is is that it runs rich all the time. Sometimes hard to start when warm, needs a bit of pedal to start, and then a puff of black unburned fuel out the pipes. Also, when warm, car will sometimes want to stall when shifting into reverse or drive from a standstill. The back bumper is always getting black specks on it when driving. Mileage seems bad too.

Did a Seafoam treatment in the tank and intake in July. Runs a bit nicer now but the other problems still presist.

Not sure what the culprit is, not familiar with the ins and outs of TPI. My first guess would be MAF sensor gone bad or dirty, or O2 sensor gone.

Please help, Thanks.

 

Could just be a vacuum leak, spray carb cleaner around the intake manifold with the engine running and listen for a change in RPMs.

MAF is expensive to replace. O2 is only ~$25, much cheaper to replace. May want to upgrade to a heated O2 sensor instead though.

Do you have a fuel pressure gauge? The pressure should be around 40 psi at idle and around 45 psi when reving the engine. Then kill the engine and watch how fast the pressure drops. If it drops immediately you may have a injector or fuel pressure regulator (FPR) leak.

To rule out the FPR: immediately after stopping the engine, pull the vacuum line off the FPR body and see if any gas in the line (indicating a torn FPR diaphragm). If no gas in the vacuum line the FPR should be fine.

To rule out the injectors: with the engine OFF, pinch off the fuel return line on the front of the engine, behind the alternator. It will be rubber 5/16ths line exactly next to the rubber 3/8ths fuel supply line. Energize the fuel pump, by bumping the engine or jumping the relay wires. The pressure should spike to around 60 psi and stay there until you release the pinched off hose. If the pressure drops with the line pinched, your injectors might be leaking, but hopefully not.

Remove the rubber air inlet attached to the throttle body (TB). Open the blades in the TB and smell for gas inside the intake manifold, or as close as you can get. This may be another indicator of leaking injectors or FPR.

What does your throttle position sensor (TPS) voltage read? You can check this with a multimeter. Measure the voltage between A and B (I think) on the TPS connector with it still connected to the TB. Turn the ignition on and rotate the throttle to look for the voltage to jump around. The idle setting for the TPS should be .54V.

Hope this helps.