1999 Le Sabre misfires engine light on and off


Asked by Mar 29, 2015 at 05:40 PM about the 1999 Buick LeSabre Custom

Question type: Maintenance & Repair

Car began missing during a ong drive two weeks ago. Minor missing with no check
engine light. Progressively got worse. Checked for vacuum leaks, none. Coil pack,
has constant flashing using spark indicator. Check engine light came on with code
p0300. Irregular intermittent misfire. Last July 2014 I replaced the upper intake
manifold with new gaskets on the lower.New PCV, IAC and MAP. The car ran great
for 8 months. Changed Mass air flow 3 years ago, ECM 4 years ago.The plugs had
over 80,000 miles so I changed them today. One was cracked #6. Now the car runs
very bad with a flashing check engine light. I shut down and I am looking for help.

5 Answers


Did you change the spark plug wires? I always change plugs and plug wires together. Check the resistance values on all 3 coil packs. If they're not within specs replace them (all 3). If 1 is failing the other 2 are soon to follow. Did you scan the computer after you changed the plugs? Is it still throwing the P0300? HTH. -Jim

1 out of 1 people think this is helpful.

Did not change plug wires. Irregular misfires have changed to a constant misfire. Dumping gas into exhaust and I think this is making the check engine light flash. Not sure how to check resistance on coil packs. .

4 out of 4 people think this is helpful.

Plug wires should definitely be changed. You'll need an ohmmeter to check the resistance on the coil packs. Yes, the check engine light is flashing to warn you that the engine is misfiring and the catalytic converter is being damaged by the misfiring. HTH. -Jim

1 out of 1 people think this is helpful.
Best Answer

Thank You Jim, Started over checking everything except the plug wires (on purpose). Changed plug wires upon your recommendation and, new engine. I;ll add this to the must do column when doing this work again. Best of luck, Randy

1 out of 1 people think this is helpful.

Awesome Randy!! Thanks for letting us know. Glad to help. Thank you for the best answer click as well! Happy Motoring. -Jim

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