Anyone have trouble with Corvette knock sensors

[zo6racerx]

I spent about 6 hours on the dyno with my friends 02 Z06 yesterday. He has AFR heads that give this car 11:1 compression. He runs 93 octane. KR started removing timing in a couple spots on the dyno and no matter how much timing I removed it wouldn't be consistent. It wouldn't be there one run and then come back slightly the next, and the a lot on the next. I was down all the way to 16 degree's. AF was solid in the 12.6-12.8 range.

So what I decided to do was turn off the knock sensors and start to add timing back in 2 degrees at a time. The car didn't lose any power or torque all the way to 26 degrees. It started not to gain any more power at that point so I backed it off 2 degrees. So it appears that these sensors are pretty crappy. Does anyone change the sensitivity on them or has anyone had a problem with them before?

[INTHERED]

The knock sensors can be a problem especially on a noisy engine. My engine has so much piston slap that I had to desensitize mine a little. But before you do this I would datalog with race gas and compare the KR between the two runs. If the KR goes away then it probably was real KR. If it is still present and your spark table seems reasonable then it may be false KR.

INTHERED

[sts-rob]

There is a TSB from gm about the knock sensors. I think in the TSB you have to remove intake and check the knock sensor for water damage they tell you to replace and make a barrier w/ RTV. had a 99 c5 doing that and the dealer had it two weeks changing everything from pcm to plugs, wires, gas ETC. The customer brought to me and the knock senors corrected the issue

[INTHERED]

There is a TSB from gm about the knock sensors. I think in the TSB you have to remove intake and check the knock sensor for water damage they tell you to replace and make a barrier w/ RTV. had a 99 c5 doing that and the dealer had it two weeks changing everything from pcm to plugs, wires, gas ETC. The customer brought to me and the knock senors corrected the issue

I think this TSB is related to cleaning the engine compartment at your local car wash with the high pressure wand. So unless ZO6RACERX's car has a history of this I would not bother taking off the intake and replacing the sensors just yet.

[zo6racerx]

Thanks for the responses please keep them coming. Like I said I was getting all kind of inconsistent KR no matter how much I retarded the timing. The car was all the way down from 26 degrees to 18 degrees and still had the same issue. I then turned the knock sensors off and started going up 2 degrees per run. The car continued making more power throughout the RPM curve all the way up to 24 degrees. AT 26 degrees it didnt make any more power but it didnt lose power so I backed it down to 24 degrees.

If it was detonating it sure wouldn't continue making more power as I increased timing. The car has AFR heads and a bigger cam/aftermarked valvetrain. The valvetrain noise has definetely increased but isn't excessive. I just wanted to see what kind of experiences other tuners had with C5 Corvettes.

[sts-rob]

Here is the TSB maybe related maybe not. The one i repaired was not ever "hosed off" engine compartment was NASTY and customer confirmed.

But good luck either way

File In Section: 06 - Engine/Propulsion System

Bulletin No.: 02-06-04-023A

Date: June, 2002

TECHNICAL

Subject:
Audible Spark Knock (Detonation), MIL Illuminated, DTC P0332 Set (Replace Rear Bank Knock Sensor and RTV Area Around Sensor)

Models:
1998-2002 Chevrolet Camaro, Corvette
1998-2002 Pontiac Firebird
with 5.7L Engine (VIN G - RPO LS1)
1999-2002 Chevrolet Silverado, Suburban, Tahoe
2002 Chevrolet Avalance
1999-2002 GMC Sierra, Yukon, Yukon XL
2002 Cadillac Escalade, Escalade EXT
with 4.8L, 5.3L or 6.0L Engine
(VINs V, T, Z, N, U - RPOS LR4, LM7, L59, L09, L04)

This bulletin is being revised to add Cadillac Escalade and Cadillac Escalade EXT to the Models. Please discard Corporate Bulletin Number 02-06-04-023 (Section 6 - Engine/Propulsion System).

Condition

Some customers may comment on a mild to severe engine ping (commonly referred to as spark knock), usually worse during acceleration and/or an illuminated MIL. Upon investigation, the technician may find DTC P0332 set.

Cause

This condition may be the result of corrosion of the rear bank knock sensor due to water intrusion into the sensor cavity. This condition is more apparent on vehicles in which customers frequently wash the engine compartment

[jimmyblue]

If the knock sensitivity creeps up on subsequent runs, this
might be a cooling problem? Air is not that good on a dyno
sitting still. Was it allowed to come back down to baseline
idle coolant temps?