Alright so here's a funny story. My car has been in the shop a couple times to diagnose what's going on but no one can ever give me a straight answer. There's absolutely NO check engine light on. It had a history code of a P0172, running rich. It still smells funny and is acting odd but nothing has come on since. The car tends to sputter or backfire when merging onto the express way, or when under moderate to heavy acceleration. It's a '98 2.4L cavalier. I've ruled out the intake and the muffler. It's had new head gaskets, new timing chain cover gasket, new valve cover gaskets, all replaced. New O2 sensors, new MAP sensor with the vacuum line. New fuel filter and pump with the lines. New spark plugs. I've honestly stumped almost every person I know with this car. Can someone please help me before i spend too much money?.................Again?

It used to run rich? Fuel rail or injectors?

well i've figured it was the pressure regulator because that's what is supposed to set off that code. but my mechanic did a fuel pressure test but everything seemed to be fine to him

Catalytic convertor ever been changed? You said it smells funny, does it smell like rotten eggs, or sulfur?


- Your not-so-local, untrained, uncertified, backyard mechanic. But my @!#$ runs

I do sometimes notice a funny smell coming from the exhaust and there is almost an unusual amount of carbon build up. i don't recall it ever being changed.

Maybe compression test the cylinders? And hold it there when testing? Perhaps a leaky/stuck valve? I don't know, throwing ideas around.

I'm with Oedwards, if you smell sulfur/rotten eggs the cat is most likely the culprit.