So this past weekend I changed out the spark plugs on my 2001 LS1. It's got a magnuson supercharger, comp cams boost cam, meth injected and all the essential goodies. I was having an issue beforehand where the car would idle funny after I got into boost and sprayed meth so I figured I would do new spark plugs and wires.

I got the NGK TR6 plugs and gapped them to 0.035 per the shop's request that tuned the car. All spark plugs were gapped correctly and put in along with the new wires. On cold start the car drove fine until it warmed up. At the next light the car was idling down then bouncing back up to it's normal idle. Took the car back home, and swapped out to the old wires to make sure it wasn't a wire issue. Car still ran the same.

Now the car feels like it's misfiring, I can feel a slight thump in the clutch pedal when engaged that happens in no real particular order, and the car bogs way down when under 1500-1800 RPM and the engine just has a different tone to it that I can't really explain. The weird thing is that the car runs absolutely perfect until it heats up a little then all these issues start happening. I had the shop that tuned it look at it real quick and they ran the scanner and said there weren't any misfires happening but something definitely wasn't right. Sucks because they won't be able to actually work on it until later this week.

They seem to think this may be an issue with a wiring harness somewhere that's apparently a common issue on these cars?? Not sure what they're talking about though. Would it be worth it to go buy a new set of plugs and swap them out again? Any suggestions here, I'm kind of at a loss for right now... Thanks in advance!!

 

I had chafing on my wire harness that threw a code. It is a somewhat common problem. It is when the harness wires rub and start to wear the insulation enough to misfire.

I googles wire harness chafing and saw a lot of post on the topic.

 

I was worried that might be the issue but I'm not throwing any codes which is weird. Could be cause the cam in the car? Supposedly it won't throw a misfire code until after 2200 rpm.

 

Mine had codes but is mostly stock. I'm sure someone more familiar with power adders will chime in.

I thought the problem i had was worth mentioning since it was an easy fix. I inspected the wire and used some liquid insulation.

 

A vacuum leak perhaps....maybe whatever seal after heating doesn't seal properly? Just putting it out there. Another thing id look into is fuel pressure.

 

Have you checked the coils?