Bomber72

had the car for a month ran great ,came up with ckj engine code p303 ,i changed all the plugs and all the coils run good for about 20 mi ,but at deceleration same code pops up ,i cleared the codes after they shoe ,could it be the ecu module/

cliffyk

Here is what the shop manual says about P0303, with possible causes and diagnostic tips.

Here is a description of how the misfire monitor works. Note that a misfire does not automatically indicate an ignition problem. The detection system monitors the crankshaft's and rotational acceleration and velocity between firings, using abnormal values of same to identify incomplete combustion.

The misfire can be caused by any one or all of: "...absence of spark, poor fuel metering, poor compression, or any other cause."

99texasGT

I have the same problem in my 99. Got new plugs and coils. Drive about 90 miles and the service engine soon light came back. Went to autozone today and I got a misfire code for #3 and 6. What the hell? Spent the bucks on plugs and coils and still misfire ****. Hey bomber72 if u figure anything out or solve your issue please let me know. I'm going out to pull #3 and 6 back out and reinstall again. Maybe there not seated good or something? Good luck and thanks