rough idle on 2002 pontiac bonneville


Asked by Feb 01, 2015 at 09:57 PM about the 2002 Pontiac Bonneville SLE

Question type: Maintenance & Repair

I just bought a 2002 pontiac bonneville and my issue is that it idles rough and the code
comes previous owner said the code comes up as a misfire in cylinder 3. He said he
checked the coil packs and replaced spark plugs and wires and also the injectors. Any
other ideas on what this issue could be? I dont have much more information as i just
bought the vehicle yesterday.

3 Answers


Compression test that cylinder. If it's low, could be a burned/stuck valve or worn rings. What engine do you have and how many miles are on it? HTH. -Jim


3.8 191000 miles

1 people found this helpful.

Have the computer scanned to verify that what the previous owner told you is correct. Most auto parts stores will do it for free. At that mileage it's safe to assume that the intake manifold gaskets have been done. They usually failed between 90,000 and 120,000 miles. If it is a "dead" miss on cylinder number 3 definitely compression test that cylinder. If it's below 150 PSI something mechanical is going on. If it tests very low or zero it's a valve. If it's not very low, say around 120 to 140 PSI, squirt about a teaspoon full of motor oil in the spark plug hole and retest it. If the compression comes up it's going to be worn rings. Did the seller provide receipts for the new parts? If not, and the compression test reveals no problems, go back over what he claims to have replaced. HTH. -Jim

2 people found this helpful.

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