Hello, I've got a buddy with a 98 z28. The car ran great when he got it, it has LT's, flowmaster catback and a baby cam, its very small but you can hear it.


The car also has a lingenfelter weiland aluminum intake. The car has for a while started to idle higher and its wierd only when 100% throttle it will misfire and ping from 3,000-3,500 RPMS and UP. If you give it 90% throttle it wont do it at all, but when its absolutely 100% it misfires and makes a bad pinging noise, is this detonation? I knew it had a vacuum leak from the higher idle, we took off the manifold today and replaced the gasket with RTV sealant, the car idles MUCH MUCH better, drives so much smoother, but still does that problem at WOT.

Could it be the WOT tune and be detonating? I know it has a very small cam, but it didnt do this when he first got it, shortly after it did though. Spark plugs are fine, as in recently changed, however i pulled one out today and it seemed a bit white on the end from gonig lean?. Any idea?

Thanks

 

I had the same problem at WOT, I had my plugs and wires changed and had it put on the dyno and they found knock and evened out the A/F and it fixed the problem. So I would start there and see how that works.