Just bought a used 2004 grand prix. Engine light popped on and it won't accelerate sometimes at low RPMs. Seems to be getting worse, sometimes it will accelerate fine and then rpms drop off and won't recover even if I mash the pedal. Took it to autozone and found that it tripped the following three codes: p0420, p0134, p0306. Hoping it is something simple like fuel/spark or clogged cat. Any help? thanks
Country: United StatesMake: PontiacModel: Grand Prix GTYear: 2004Engine: 3.8 v6
autozone to pull codes, nothing else. I know the previous owner said he was running low octane gas for a long time.
Hello, thanks for the quick response, it has 155k and lacking any service records
Can a bad cat be causing the misfire on cil 6??
Sorry for the delay in getting back to you. Please hold your ratings until the end. As for your follow up question, typically the converter will not cause a misfire on #6, but the misfire on #6 will cause the converter to fail. My follow up to you was to let you know that once you find out of if the converter is bad you need to fix the problems that caused the failure like this misfire. It may be due to an ignition system issue or a problem with a leaking intake manifold or a valve issue. Do you plan on fixing this yourself?
Thank you for being helpful, just one more question. It had no power this morning and I barely made it to a gas station but then I filled the tank up all the way and now it seems to be driving without any problems!?! Does this make it sound more like fuel system issue? Could you just give me the top three things you think I should get looked at and tell me what you would do in my shoes? Thank you for all your help
Due to the various symptoms that you have and the codes that are coming up I would recommend having the misfire fixed first as well as having the fuel pressure checked. The fact that the vehicle runs different with more fuel indicates a problem with the fuel pump. These are the place to start as they will cause the converter to fail. There is no sense in installing a new converter and having it fail again until fixing these other problems first. I would ask the shop to diagnose the vehicle and use what you now know to determine if they are being truthful. if you have questions about what they tell you then let me know and I will help you.
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