Running Out Of Ideas (98 GTP)

[86TATpi]

1998 Grand Prix GTP
Approx. 86,000
Runs fine until the temp. reaches between 188 and 210, then engine starts to surge, blows black smoke from exhaust. The car won't run until it cools down. There is no service engine light. Tech 2 shows everything is operating normal. The car was just tuned up, including oxygen sensor, fuel filter, air filter. Supercharger is new (had bad nose drive and supercharger was leaking oil) problem doesn't seem to be related anyway, ran the same with old s/c as with the new one. When a spark tester is hooked up it sparks fine (when trying to start it up again). I need to check the fuel pump, when it primes it will just barely be under the minimum 48 psi. I wasn't sure if a bad pump could do this, but nothing surprises me with OBD-II. I haven't been able to find much info about the boost solenoid or how to check that. If anyone has any input it would be greatly appreciated.

[GTP Dad]

Fuel pressure is important on SC cars, but I would check the pressure regulator and replace it first before going to the expense of changing the fuel pump. You might want to check the EGR circuit. It may be blocked with carbon. This could cause the problems you are speaking about and not show a problem in the computer unless it were completely blocked or the valve was bad.

[86TATpi]

The egr seems to be ok. Fuel pressure drops off from 44 psi to mid 20 psi after sitting for a couple of hours. Not sure if that is normal. Just today the car had a SES light. Hooked Tech 2 up to the car (it was sort of running) and it had code P0103. MAF sensor frequency output high. Problem is when I went to the engine data display the frequency was at -15,000 hertz. And it said it was metering -300 g/s. Unplugging the MAF makes the car run better and there is approx. 11 volts going to the sensor with KOEO. It trips this code if voltage is over 8 volts. I guess it's time to check wires going to PCM. Hopefully all this comes to an end. Again any suggestions are appreciated and checked. Thank you.

[86TATpi]

The problem turned out to be the Mass Air Flow sensor. I hope that if anyone has a similar problem that some of this helps.