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P0202, P0204, P0300 2004 Grand Prix N/A *Need Help*



yup, its the lump in the down pipe between the engine and the cat back flange. if you have a u bend in that year its right before it. (where the o2 is)
 
Scottydoggs said:
yup, its the lump in the down pipe between the engine and the cat back flange. if you have a u bend in that year its right before it. (where the o2 is)
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thats what I thought. Yeah i have that stupid u bend. If it ever comes to replacing the cat the u bend is going with it.
 
Maybe the spark plugs in the 2 cylinders that were missing were still fuel-fouled from running too rich, and causing the miss - your test drive probably cleaned them up enough to let those 2 holes start working properly again. I'd change the oil at this point now. It may be a little diluted with fuel from running so rich.
 


kmohr3 said:
Maybe the spark plugs in the 2 cylinders that were missing were still fuel-fouled from running too rich, and causing the miss - your test drive probably cleaned them up enough to let those 2 holes start working properly again. I'd change the oil at this point now. It may be a little diluted with fuel from running so rich.
Click to expand...

The plugs were brand new and I just changed the oil as well. The car is still fine 6 days later and probably 250-300 miles driven.
 
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