Cant trace a misfire

[LeoC2]

Moose developed a misfire on cylinder 7. Usually when this happens I just replace the coil pack and that's it but this time no luck. I replaced the plug and coil but still get the misfire. Where should I look next?

[LeoC2]

NEVER MIND! Would you believe this? Luckily I bought two coil packs because I always keep a spare in the trunk just in case. I had a suspicion about the one I put in because it was not packed in bubble wrap inside the box like the other one was. I swapped them out and voila, everything runs fine. The coil pack was bad! In fact it was even a different color than the other. I suspect someone returned their old one to the store for a refund claiming it was one they just bought.

[driller]

67 minutes... not too shabby.

Dare I ask what brand coils?

[LeoC2]

67 minutes... not too shabby.

Dare I ask what brand coils?

Box says "Standard T-Series" I've always bought Motorcraft or even Accel in the past, I needed this prointo so I hit the local auto parts store and this is what they had.

[tixer]

I ran a couple of those "standard" coils for a year or two. Never had any trouble with 'em. Glad you got 'er fixed.

Later on, I got a great deal on a new set of 8 OEM coils, so I switched to those. presumably, they're still in the car today. Unless Kirk took 'em when Eric wasn't looking..

[LeoC2]

I may have spoken too soon! All of a sudden I now have a rough idle and a sensation of a misfire buy no code yet being thrown. What else should I be looking for?

[tixer]

My solution was always to wait. given some time, it will detect the misfire. If I had to guess, you have more than one coil giving you trouble.

[LeoC2]

Still showing a misfire on #7 even after changing out coils twice. So now where do I look?

[driller]

My next step to diagnose such an issue would be to swap the coils around and see if the problem follows the suspect coil or stays with the same cylinder. You could take it one step further with the plugs.

If the codes indicate the problem follows the coil or plug, you have found the component at fault.

If the problem stays with the cylinder despite a different coil/plug, the issue will be with the harness plug, wiring or possibly the PCM.

[tixer]

double-check the gap on the plug?

I know they always /say/ they come pre-gapped... but I know better.

Usually because I trust them, install all the plugs, realize it runs like crap, and /then/ pull all the plugs and check the gap to find they're wrong..

[LeoC2]

"My next step to diagnose such an issue would be to swap the coils around and see if the problem follows the suspect coil or stays with the same cylinder. You could take it one step further with the plugs."

Ha, that's exactly what I did and sure enough I'm now getting a misfire code on that cylinder. Has to be a bad spark plug unless the parts store sold me two bad coils which is unlikely.

[LeoC2]

Replaced the plug and all is well in Mosse-land now. I honestly can't remember when I've ever had a spark plug fo bad on me.

[driller]

Glad you got it figured out.