05 Deville po300 code

Question

Car starts but shakes a lot. When in gear, the car wants to shut off. When I press the gas it looses power and engine smokes a little. Any ideas before I start to work on engine??

Answer 1

Hi there

P0300 is a multiple misfire code, or could be there because the computer cannot determine which cylinder is misfiring. Sometimes with the engine running you can unplug a coil, if the engine runs worse, plug it back in and move to the next. If that one doesn't make any difference on the way it's running then it's a bad one.

Do this for all of them just one at a time and see which cylinders are actually the problem. Then swap the coils around and see if the problem moves with the coils. You can also inspect the coils and plug boots for any burns or marks where the spark has been arcing. Also, if you find any with oil on them they are possibly problems because the oil will eat the rubber boots.