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08 misfire aftermath
Posted: Sun Apr 18, 2021 6:05 pm
by HazmatikNC
I recently purchased my 08 SE about a month ago with 98k miles and have put about 750 miles on it since and had it start idling rough and losing power. First thing I did was replace the spark plugs (got to learn how to dismantle the intake plenum to get to the passenger side ones) after replacing the plugs it was still idling rough and the CEL came on and flashed and I noticed a small amount of fuel dripping from the exhaust. I ran the code and it came back as cylinder 6 misfire, I then swapped the ignition coil from #6 with #4 and ran the codes again and it came back as cylinder 4 misfire, so I replaced the bad coil and it is no longer misfiring, leaking fuel, or throwing codes. I have however noticed it is still idling a little rougher than it did before the misfire, not near as rough as when it was misfiring but still rougher than before. Is there something else I should check that could have possibly occurred because of the misfire? Should I replace the other 5 coils as well?
Re: 08 misfire aftermath
Posted: Mon Apr 19, 2021 2:51 am
by ShipFixer
HazmatikNC wrote: ↑Sun Apr 18, 2021 6:05 pm
I recently purchased my 08 SE about a month ago with 98k miles and have put about 750 miles on it since and had it start idling rough and losing power. First thing I did was replace the spark plugs (got to learn how to dismantle the intake plenum to get to the passenger side ones) after replacing the plugs it was still idling rough and the CEL came on and flashed and I noticed a small amount of fuel dripping from the exhaust. I ran the code and it came back as cylinder 6 misfire, I then swapped the ignition coil from #6 with #4 and ran the codes again and it came back as cylinder 4 misfire, so I replaced the bad coil and it is no longer misfiring, leaking fuel, or throwing codes. I have however noticed it is still idling a little rougher than it did before the misfire, not near as rough as when it was misfiring but still rougher than before. Is there something else I should check that could have possibly occurred because of the misfire? Should I replace the other 5 coils as well?
I had a bad ignition coil a few months ago. I felt like it needed a while for the ECU to get used to the new coil if that makes sense...seemed like it was a little rough but smoothed out over time. If you're not throwing any more codes over time then you are probably okay, but some take a long time to show up.
Re: 08 misfire aftermath
Posted: Mon Apr 19, 2021 5:07 am
by lebowski
Don't know how expensive a coil is, but I would replace all of them. They all had the same amount of miles.
Re: 08 misfire aftermath
Posted: Mon Apr 19, 2021 11:27 am
by smj999smj
You can get genuine Hitachi ignition coils from Rockauto for $35 each. I'm not saying that's your issue, but FYI. Idle roughness is usually on par for many VQ engines and the 4.0L is no exception. You could try performing an idle air volume relearn procedure. It wouldn't hurt to check the front motor mounts, as there have been some vibration issues caused by bad mounts. Bumping-up the base idle a little helps cut down the vibration at idle, but this requires a capable scan tool or a tuner. FYI, you don't have to remove the upper plenum to replace the #1 and #3 coils, although it takes a bit of patience and ingenuity with reducers and universals. Better yet, install an XTP plenum spacer that makes the job a LOT easier and increases mid-range power at the same time!