Ok, i have a 03 silvy, it has 100k miles on it, i dont usually run it hard at all, but when it hits about 5500 rpms, i can hear some ruckus coming from the engine. it sounds like world war II under the hood, then it throws a code saying misfire cylinder 1.......what should i do? it almost sounds like valve clatter. i do have it tuned but i do run what it is tuned for as far as gasoline (93).

 

have you changed your plugs in the 100k miles??? it may be time for some new ones. you can swap your coil, plug, and wire on a different cylinder, go drive it and see if your miss follows 1 of the 3...

 

I had almost the same exact problem with my 03 Avalanche with 119K miles. Anything above 3500/4000 RPM, all sorts of nasty noises and the misfire codes on 1,3, and 7. Turned out the catalytic converter on that side had decided to self-destruct and plug the exhaust. I knew it was broken, as it was rattling for awhile, but didn't expect it to suddenly plug up the works.

Good luck.

 

damn, well i did change my plugs, and i did replace the coil pack........the codes arent showing up there anymore but the noise is still there. i just ordered some long tubes so away with the cats and we will see if thats the next thing.

 

YEAH CATS ARE REAL COMMON FOR RAISING HELL AT HIGHER RPM'S AND IF IT IS THE CAT JUST BE HAPPY THE PIECE HASNT LODGED IN THE OUTLET AND CAUSED MAX BACKPRESSURE.... TAHT TURNS OUT BAD

 

Pull your plugs and check them.

 

check them for what, i just changed them a couple hours ago?

 

just chill out and see what happens once the long tubes are in there, you probably have a bad cat - my old truck killed the cat with 55,000 miles on it, wouldn't' be a surprise for you to have one going out.

 

Did it start doing it after or before the plug change? I was understanding that it was after. If it was doing it before then there is no need to check them. I was going to say check for gap or oil or gas

 

Mine did that and it was the hot weather + too much timing. Had some timing taken out and problem solved.