Sputter/backfire and sulfur foul smell on heavy acceleration


Asked by Oct 05, 2015 at 08:17 PM about the 2000 Pontiac Grand Prix GTP Coupe

Question type: Maintenance & Repair

Changed iac,maf,tps,fuel pressure
regulator,fuel pump, air filter, fuel filter,
csps, egr, oil change, exhaust
work(mufflers) and ignition module. Got the
car to stop stalling on start and runs great
besides odd idle and foul smell on heavy
acceleration. Only things I haven't changed
are plugs wires, coil packs and injectors. I
cant find an evap leak but line from gas cap
to fuel tank are rusty.

5 Answers


Also have codes p0102, 0440, 0306

1 out of 1 people think this is helpful.

Sounds like catalytic converter is getting bad.


P0102 is Mass Airflow Sensor circuit, low input. Possible bad connection or bad sensor. P0440 is an EVAP system leak. The system is leaking vacuum. Gas cap is #1 cause for this trouble code. P0306 is misfire on cylinder #6. Do you have an aftermarket air filter, such as a K&N, which requires oil? If so, get rid of it! The oil contaminates the Mass Airflow Sensor. The sulfur odor is most likely the catalytic converter overheating due to the misfiring on cylinder #6. HTH. -Jim

Best Answer

I do have an aftermarket air intake came with the car when I bought it 2 years ago have never oiled it just changed the cone filter on it about a year ago when I did the first maf sensor. I have gone through 2 maf sensors in the last year the second one about a month ago when I changed the iac , tps, and crank sensor. Also cleaned the throttle body while I was at it but didnt check any of the connections so ill take a tomorrow and get a new gas cap. As far as vacuum leaks I haven't been able to find one under the hood any of the times ive checked but im going to put a stock air filter on it and ill get back with the results. Thanks for the answers guy much appreciated!

1 out of 1 people think this is helpful.

Ok, sounds good. You're welcome. Glad to help. Thank you for the best answer click. -Jim

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