Hello all, 2000 Bonneville been running rough at high acceleration blinking SES. When code pulled it was P0306 misfire cylinder 6. Before working on it I pulled the code and now jump to P0300 random misfire. So I went ahead and changed the coils and ICM and took the car for a run at high speed and it did the same thing code was still P0300 random misfire, Yesterday I put new Spark plugs and took it for a run and again it misfired but now it read P0305 misfire cylinder 5… I was reading several forums here and they mentioned checking the fuel injectors however, what can be the cause of my SES codes jumping from P0306 to P0300 then now to P0305.Can there be something in my fuel rail jumping around?

how old are your plug wires? 306 is cylinder 6, 305 is cylinder 5, 300 is random misfire.

If your wires aren't too old I would check them all again to make sure they are tight

Hey Danthurs, the wires are about 9 months old i did take a look at all of them when installing the plugs and they were in good shape.

What kind of plugs do you have? Check the tip. I've seen a few with screw on tips that get loose. This will cause a misfire.

I put AC Delco platium spark plugs 41101 no screw tips..The ngk that were in there had the the screw tips. I did check to see if all my wires were tight after pulling the codes every wire was intact tight. I was thinking of messing with the fuel injectors but should i look at something else first since the codes are changing on me.

Pull those plugs and look at them. those are the wrong plugs for a supercharged engine. Get autolite copper. No platium plugs. They melt and cause misfires.

Really..I picked these from rockauto parts catalog the supercharged option..Do you know the part number on the autolite?

I believe you need the 605

Do platnium plugs melt rite away since they are new or does it happen with time ? I guess i'll try changing the plugs first to see what happens.
Thanks i'll keep u posted.