2002 GT
Shadetree mechanic and I'm really bummed. This only started within the last couple weeks when I went to pass a semi on the freeway and the car started jerking after giving it a lot of gas very quickly.
My first guess on this is fuel delivery issues obviously. I pressure tested the fuel lines and it shoots up to 55 psi then loses pressure quickly. Fuel injectors, fuel pump/filter, fuel pressure regulator...however, today the car started idling VERY rough and I could smell rotten eggs coming from the exhaust. Am I correct in assuming that catalytic converter problems are not the problem per se, but instead a symptom of something else happening "upstream" in the exhaust system?
OBD-II code P0420 indicates a CAT problem, but P0300 indicates I have random cylinders misfiring. So am I also correct to assume that fuel delivery issues are causing the misfires and thus the CAT problems or am I way off?
I smell a hint of gasoline on my dipstick and it takes a couple seconds of cranking to start, then dies quickly. On the second try it will stay running. Granted it's idling rough. It takes off from a stop fine, but when giving it gas in anything over like 3rd or 4th gear it just hesitates and jerks terribly. Wtf is happening here? Is it losing power because of fuel issues or misfires? Or is it both? Did I waste $100 on a fuel pump/filter combo?
I'll be replacing the fuel pump and filter when they arrive later this week (though somehow I'm skeptical that's even my issue here). Until then, it's my daily commuter (40 miles both ways, 5 days a week) because I can't get parts again until I get paid on the 1st. If I lose my car, I lose my job.
I don't have access to any professional diagnostic equipment. Aside from just adding oil and coolant, I have never really worked on any car, ever, as I have never had anyone to teach me. Recently, I swapped the upper intake manifold and lower intake manifold gaskets with aluminum Felpros by myself. Swapped water pump, oil/filter and coolant as well during that project. Watched Youtube videos and read a couple forum tutorials. I didn't find it terribly difficult, just time consuming, and this gave me a lot of confidence and I really want to learn everything about how this car works so I can just care for it myself. It just past 130K and I hope to keep it past 300K.
This is my second sixth-generation Grand Prix GT and I'm really in love with the cars and especially the engines. I think they're wonderfully engineered other than a few minor flaws that aren't that difficult to iron out yourself with a little willpower. This is also my first post here and I hope to be a member for the forseeable future! Down the road, I eventually plan on buying a 7th-gen GXP
I really do appreciate any guidance you guys could offer a new shadetree mechanic.
EDIT: I am aware my CAT is done for, I assumed that they go bad because unburned fuel causes the honeycomb filter in them to melt, break into pieces and thus plug them up, or is that wrong? What's the saying, "cat. converters don't die, they're murdered"? Is the fuel in my oil unrelated?
