misfire in the 3rd cylinder

[CamaroRScrazy]

1996 Camaro RS V6 3.8L.

I just changed the spark plugs several days ago. Last night when I was driving, the 'Service Engine Soon' light suddenly went off and kept flashing. I can feel the engine was rough. Scan showed a code P0303, 'third cylinder misfiring'. I checked the ignition using a ignition tester, it is sparking.

What can be the reason?


Any advice will be greatly appreciated!

[Blue Bowtie]

1. Are you certain you are getting spark to the #3 cylinder when the engine is running? An inline spark tester works best for this. It is possible that a weak spark could show up on a tester while cranking but not in a cylinder under compresion pressure. It is also possible on a wasted spark system that a plug which is fouled with deposits, fuel soaked, or otherwise damaged will allow the opposite cylinder to fire but not permit spark itself (It just shunts all spark energy to ground).

2. Are you certain you are checking the #3 cylinder? Buick engines have a different cylinder order than Chevy V-6s.



3. It takes more than ignition to make a cylinder fire and produce power. The fuel injector must also admit fuel, and the valves must open and close at the correct time to cycle the fuel and exhaust through.

[CamaroRScrazy]

I just found out that the misfire is caused by the looseness of the spark plug boot. I just pushed it further and heard a click and then I cranked the engine and it works well again.


Thank you so much for the reply! I learned a lot.