I have a 2004 Grand Prix v6. I got my coils checked and number 2 fire was real weak while the others are strong. Could that be why it's showing a misfire on cylinder one? I took it to AutoZone and they detected it.

  • Do I understand that it overheats while at idle but temp is normal while driving? How long does it take for the temp to return to normal?
    – mikes
    Jan 6, 2014 at 23:02
  • I suggest asking two separate questions. Edit this question and remove either the overheating or misfire, and ask a new question for the other. Jan 7, 2014 at 2:03
  • Yes mr.mike that is correct.an it didnt take no tim e to go back down maybe.a min or two
    – user4267
    Jan 7, 2014 at 14:04
  • Ok mr.larry will do
    – user4267
    Jan 7, 2014 at 14:08
  • Were there any codes? Is the CEL on? Did Auto Zone check the coils? If so how? Jan 7, 2014 at 15:03

3 Answers 3


In GM engines, a cylinder #2 misfires usually indicates a bad coilpack. Not always, but usually. To answer your question, yes, a poor spark will sometimes cause a misfire.

The correct way to check what's wrong is to swap two HT leads around (the cables coming from the coilpack and plugging onto the spark plugs).CAUTION: swap them at both ends so that you don't make them fire out of sequence. If the misfire stays on the same cylinder, it's not the lead, it's the spark plug or the coilpack, else it's the lead.

Next, swap two spark plugs around. If the misfire is on the same cylinder, and it's not the lead, then it's definitely the coilpack. Else it was the spark plug. Replace as necessary.

Also take note that a bad coilpack or HT lead will foul the spark plug in the misfiring cylinder. Best practice is to replace sparkplugs when doing the coilpack. It's also a good idea to replace the HT lead for that particular cylinder.


Firstly we need to know if the HT cables are in good condition (measure the resistant) If not enough antifreeze used on cooling system rust will block thermostat (which will cause over heating)

  • Mr dick wat are ht cables? An when i took car to auto first time the said i needed a..o2 sensor ..a misfire in cylinder one an my themostate was below ..i got o2 sensor an.check engine light stil on ..so i took it back to auto zone then the only thing it detected was misfire oncylinder one .it no lon lone
    – user4267
    Jan 7, 2014 at 14:15
  • It no longer detected that themostate was below..so wat u think
    – user4267
    Jan 7, 2014 at 14:16
  • Did o2 sensor do the job for that
    – user4267
    Jan 7, 2014 at 14:17

this is old school but you never know.Could be a dud s/plug.Take out plug/refit lead/out of gear/h-brake on.Use thick gloves and place plug end on block.Have someone turn engine over and check for spark May not be your problem but good to know.

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