2003 Pontiac Bonneville p300 p420

2003 PONTIAC BONNEVILLE
V6 • FWD • AUTOMATIC
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KNISALAD
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  • 1 POST
I've had this problem for over a year now. sometimes car idle smoothly, others it chugs hard, almost stalls itself out/ battery fluctuates. When accelerating easy it runs normal. when accelerating heavy there is a loud chirping/ squeeking noise, then the engine shakes violently, and has very little power. Replaces MAF sensor/ air filter one year ago. Spark plugs/ fuel filter 2 years ago.
Apr 18, 2015 at 9:27 AM
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HMAC300
  • CAR REPAIR CONTRIBUTOR
  • 48,601 POSTS
code 300 is a misfire and a pro should diagnose this as it can lead to buying a lot of parts that are not needed. code 420 is a converter code which means if it's not a bad O2 sensor or air leak prior to converter you need a new one which you didn't post mileage so I suspect it's a lot on the car.
Apr 18, 2015 at 10:32 AM
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