I have struggled with a slight miss only at idle from one cylinder for about a year now. It has just recently become worse where it will show up when cruising at >1200 RPM. It only happened when hot and pulled great all the way to redline. There are quite a few threads where members have reported the same symptoms, but never really figured out the cause. Here's a little info about my car assuming everything not listed is a stock GTE....
Rebuilt 7MGE. NA-T.
3in DM DP.
Flow tested and cleaned 440's.
Extra coil pack and igniter grounds.
Rebuilt harness. Coax knock sensors.
MBC @12 psi
Full flow oiling system.
By power balance checking each cylinder I found #4 to be the weakest and source of miss. I swapped plugs and coils with a good cylinder and compression tested all cylinders. All at exactly 195. Miss was still there. Hose down ignition components to check for arching, including with hood down. Blocked off EGR. Miss still there.
Next I smoke checked intake. Fixed a few leaks and got it down to .003". At this point I ruled it down to primary ignition or fuel delivery. I scoped the primary ignition signal to each coil pack. All good, so that rules out everything in the ignition circuit. Now this left me with only fuel delivery. I ruled out fuel pressure as that would affect all cylinders. With a noid light I checked the pulse of each injector and found nothing odd. I also resistance checked them all. One thing I found odd was that the #4 injector had about 3 times the noise and vibration when I put my finger on it.
Swapped another injector with #4 and Walla! Miss gone. These were flow tested and clean injectors with less than 5k on them. A clogged injector will mimic a secondary ignition miss, so don't let it fool you!
Rebuilt 7MGE. NA-T.
3in DM DP.
Flow tested and cleaned 440's.
Extra coil pack and igniter grounds.
Rebuilt harness. Coax knock sensors.
MBC @12 psi
Full flow oiling system.
By power balance checking each cylinder I found #4 to be the weakest and source of miss. I swapped plugs and coils with a good cylinder and compression tested all cylinders. All at exactly 195. Miss was still there. Hose down ignition components to check for arching, including with hood down. Blocked off EGR. Miss still there.
Next I smoke checked intake. Fixed a few leaks and got it down to .003". At this point I ruled it down to primary ignition or fuel delivery. I scoped the primary ignition signal to each coil pack. All good, so that rules out everything in the ignition circuit. Now this left me with only fuel delivery. I ruled out fuel pressure as that would affect all cylinders. With a noid light I checked the pulse of each injector and found nothing odd. I also resistance checked them all. One thing I found odd was that the #4 injector had about 3 times the noise and vibration when I put my finger on it.
Swapped another injector with #4 and Walla! Miss gone. These were flow tested and clean injectors with less than 5k on them. A clogged injector will mimic a secondary ignition miss, so don't let it fool you!
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