Hi guys, I'm hearing what appears to be detonation, however slight. This is going to be on an '89 LO3 with 70k. I only hear it when giving it gas and its there almost 100% of the time. Its not very loud, but it sounds identical to detonation.

It made this noise even with the timing being 4 degrees retarded. I then adjusted the timing correctly to 4 degrees advanced. The sound is still there. I then tried a higher octance fuel and I still hear it.

I did notice that my knock count was a bit high. I saw over 70 counts only about a minute after startup. I'm also not ruling out a carbon buildup but I did have GM Top Engine Cleaning performed. Anyone have any comments?

Adam

 

I've got the same problem, only not quite as severe.. mine does it under load at low rpms when at normal operating temp.
I've ran cans of seafoam through it.. shot out a bunch of carbon, problem still ocurred, I have timing at -2* to keep it from doing it most of the time. I tried the higher octane in the past and it didn't fix it. I think I've got a vacuum leak. Most likely in the stupid little hosses, but I'm going to check around the intake and TBI unti base.

Unless you've done it already Annihilator, I'd suggest the same.. that will give you a lean condition causing detonation. I remember there being some posts on here about searching for vacuum leaks, but havn't been able to find any. I'm going to use propane, but starting fluid, ether, and other flamable materials can be used. You just need something that will cause the engine to rev when introduced so you can tell where the leak is located. I would start by going over all the vacuum lines first though.

I really want to get this problem fixed so I can bring the timing back up to +2* and get the tires to chirp again when shifting.. this slow sluggish driving is real depressing.

 

I actually did find a vacuum leak recently. My car felt like it was missing until it warmed up and it ended up being a hole in the vac hose coming off of the MAP sensor. However, now i get that same miss when i shift out of park or neutral so I'm guessing there is another leak. I already replaced the TBI Gasket. I'm going to replace all the hoses and see where that takes me. This noise is really pissing me off :P

 

vacume leaks can cause a lot of weird problems to bad we have so many vacume dam vacum lines!

 

Have you checked your headers gasket? I know it may sound simple but I've just done all the seafoam,higher octane, timing,coil..etc and although the knocks are quieter and the cars happier theres still noise that sounds like knock,happens under the same conditions and sounds like things are rattling away in the engine. I figured it because the sea foam smoke billowed out where it shouldn't, and when I tighten the header bolts it quitens down.
Hope that helps..