I hope somebody else has had this problem and can tell me what they did. Some quick info: 6 degrees base timing, about 30-31 advance during light acceleration and full throttle. My problem is the knock sensor pulls out 10-11 degrees timing under light to moderate accelaration in third gear, and 7-8 at full throttle in second gear on the street and third gear on the dyno. The car was running way to rich(A/F high 11's at full throttle on dyno). Everybody I have spoken to says its not detonation, just noise. But it's killing horsepower I'm sure. Motor has aftermarket hydraulic roller lifters with tie bars(no spider) adjusted one turn after zero lash, full roller rockers, headers, and polyurethane motor mounts. I already tried installing the knock sensor just snug with teflon tape and it did nothing. I've heard of guys "bypassing" the knock sensor and was wondering what that means. I've also been told to mount it elsewhere or try to insulate it from vibration(obviously has to be grounded to work). I thought about grounding it with a wire and mounting it in the end of a short rubber hose near where it is now. Any thoughts?

 

You sure you don' have a header pipe or something hitting the frame? Also make sure it's plugged all the way in, I had that happen to me once, it was plugged in, but under power it would pickup counts, and it turned out it came partially unplugged. Give soem more info on your setup. I'm running the same lifters and mounts on mine, no problems.

 

My exhaust was touching my oilpan so I thiught that could be it. Had it fixed, and the problem is still there. The exhaust does not rub anywhere now, and there are no header leaks at all( no black deposits on the heads which are painted red). The plug is also snapped on all the way. I'm running out of ideas. What other info would you like? I'll gladly list anything else about my setup that might help. If anybody else who has viewed this has similar parts and no problems please let me know. If you guys don't have scanners let me know that's why you haven't replied. I'm getting really frustrated with this and I want to figure it out. A few more responses would be greatly appreciated. Thanks.

 

Have you checked your fuel pressure under WOT? I am having an issue with a dying FP. Seems that it wont hold up under WOT and is starving the engine, causing high knock counts. Other than that, I only know of the exhaust nosie, and it coming unplugged.

sorry if this doesn't help.

 

While were on the subject.....do you have to run a knock sensor or will it screw up your timing?

 

Fuel pressure held very constant during dyno run. I was told being too lean could cause detonation, but the car was too rich during the last dyno session. I had one other thought, I'm using non-self aligning rockers with guideplates, wonder if that's part of the problem?

 

I remember reading one time that the LT4 engines actuall had to use a different knock sensor because the valvetrain made more noise than the LT1's. Any chance of something going on in the valvetrain?

 

I read this too. The LT4 used a different spark control module because of the roller valvatrain. This is a different component though from the actual knock sensor and it won't work on an L98.

 

Have you tried just leaving the KS unplugged?

 

I have the Exact Problem and Syptoms and the same abotu of degrees being pulled out. I have changed my maf, esc, ecm, egr, tps, and knock sensor with no change (BTW I got the stuff for free when changing) I cannot figure this out. This is also an intermitant problem for me.

 

My 89 firebird is TBI, so I'm not real familiar with the 3rd geb TPI setup, but my 89 Vette had the same problem. It turned out to be the ECS module. Here's the tech article on it. Hope it helps.

http://www.corvetteforum.com/techtip...D=99&TopicID=2