My car has been sounding a little rough when cold on startup and I have had some vibration at 40-60 mph. I figured it might be a bad coil so I bought one and started swapping. I thought I might have guessed right when my idle started at 2300 instead of 1900 or so. I had a wet well, so I tried that one first. No better. The #8 plug didn't look so good when I did the tune-up last week, so I tried that one next and that did it.
I had no check engine light, and it really didn't seem to be a "dead" cylinder. It never missed at idle like my other LS did. It seems that sometimes these coils are "kinda" bad. Strange... When the car was warm and after several miles of driving, it drove perfectly.
I can't take it down the road for a real test, as the front-end is in peices.
Just thought I would share, as the symptoms might not be as standard as some of the other posts here.
I had no check engine light, and it really didn't seem to be a "dead" cylinder. It never missed at idle like my other LS did. It seems that sometimes these coils are "kinda" bad. Strange... When the car was warm and after several miles of driving, it drove perfectly.
I can't take it down the road for a real test, as the front-end is in peices.
Just thought I would share, as the symptoms might not be as standard as some of the other posts here.