morris

I was driving the car on the highway at 60 miles per hour and all the sudden I got a rough idle no check engine lights or anything. I thought maybe I had a spark plug wire burn through as I have had similar symptoms once or twice before and that was the issue. I finally decided assess it today. I pulled the plugs on one side of the engine 1 plug had excess fuel on it compared to the others.I changed that spark plug wire and there were no changes.next step was to have the car running and pull the spark plug wires from the coils to see if there is any change in engine note, I really couldn't detect any but that's due to the heavy lope of the k501 cam. What I did see is that there was a very heavy spark jumping from the coil of each pack as I pulled the wires with the exception of two coils. One of the coils was the one with the excess fuel the other coil was on the other side of the block and I have not had a chance to check that plug yet as the engine is still very hot. My question is is it possible that I had a weak coil all along and then a second coil started to go bad or is now week and that is now why I have the rough idle and loss of power. I could just go and buy 2 new coils but I'd rather have a little higher level of certainty before I drop $140 on two coils that may or may not resolve the issue. Thanks for your advice.

morris

ok I pulled all of the plugs only the first one had excess fuel on it and that one is the one that the spark looked the weakest so I guess I will try one new coil pack for that.

redtopz

Curious of your outcome. I'm still running the original 1999 coils on my C5 race car. But I have noticed these engines are SUPER sensitive to plug wires and good connections. Every time I or other guys at the track have had a similar issue it's been plug wire related. OEM wires seem to work best, but I'm trying some new ACCEL ceramic coated wires now to see if they will work as well without burning up on the headers.

0Anthony @ LGMotorsports

What ever you do with the wires on the car, make sure you keep the stock metal shields on around the boot to the cylinder heads.

redtopz

I agree, but these new plug wires won't let you do that. You should buy a set and check them out. I'd be curious what you think. My friend has them on a 600 hp C5 and he's racing ST1/ST2 with no issues. I just bought a set and they look great, but I haven't tried them yet. Make sure you get the ones listed below for the 8.1L big block as they will plug and play with any LS engine.

http://www.summitracing.com/parts/ac...make/chevrolet

0Anthony @ LGMotorsports

We ran into an issue with another car in the shop that had a lot of extra wiring (data loggers, camera system...) and there was so much electrical noise it was causing a hot miss.

Those metal shields act as another ground for the plugs....problem solved with stock wires and shields.

redtopz

Oh I remember seeing that on facebook. That's good info! I've run without those shields before with no problems so maybe it takes the right circumstances for that to become an issue. I'll let you know how these wires work for me.

morris

So I changed the coil and there was no change, so I am not sure what the cause is, I decided to leave it alone for a few days. I have stock wires on the car and have not had the metal shields on for at least a couple of years. thanks for the responses though

0Anthony @ LGMotorsports

Bad plug? Plug gap? Wire?

Rare I have seen a coil go bad on them, but if they do they generally die completely.

froggy47

Have you read the CODES on this?