DAVE00

iTrader: (10)

Guys,

Here's my dilema. I am picking up knock on my PCM (seeing it thru Datamaster) and it's pulling upto 12 deg timing. Now I cannot hear any audible knock whatsoever so here's what I've checked so far:

• Fuel Pump - New Racetronix and putting out the proper pressure
• KS circuit is stable at 5v
• KS is new and tq'd to 14flbs with no thread sealer
• No arching of wires
• Car doesn't seem to miss (however it's hard to tell with this choppy cam)
• Injectors all OHM out properly
• LT4 KM is installed
• No exhaust rattles, or leaks
• No vaccum leaks I can find
• Pulled VC's and the rockers look fine and are not loose

Now, I swore it was the KS picking up false knock so I replaced it. Before the new knock sensor it was picking up knock all over the place - randomly - and now it's primairly picking up knock at idle and pulling 12 deg at Idle? What else can I check? Could the plugs be bad? Check the resistance of the wires and see if I have a bad one?

Solomon has tuned my car and some guys say that his high timing can cause knock, but I have installed an old tune (before Solomon) and it still picks up knock the same?

I'm pulling my hair out here, any help is much appreciated!!!!

RamAir95TA

iTrader: (2)

The PCM will retard timing far before you can hear any audible knock, so that doesn't help in the diagnostic department.

I would run some 100+ octane to determine whether or not the knock is real or false. If it turns out to be false, then have the KS circuit desensitized.

DAVE00

iTrader: (10)

Thanks man, the only problem is I have a full tank of 93 in there now and the car is really not driven much at all. I know your going to blast me for this, but can I boost my octane rating some how with this 93? Also, could bad plugs/wires cause this?

quik95lt1

iTrader: (7)

could try some really strong octane booster but 99% of that stuff sucks lol...........get a hose and a can lol

moehorsepower

iTrader: (3)

I had knock at idle and when I just touched the gas it would go away, Granted I had a supercharger but it was so close that at idle it was vibrating against the block causing the ks to pick it up, You sure no headder or Y piped is close to the K member or anything like that?

DAVE00

iTrader: (10)

Positive, as I'm running Mids and have good room and the Y is a custom Y and fits nicely all around. What you described is exactly my issue as when I give it gas the Knock goes away very rapidly.

moehorsepower

iTrader: (3)

another thing, does it do it only on cold start ups? does it go away after the engine warms up? Reason being, Forged pistons tend to have some piston slap when cold until they heat up and expand. but I would not worry about that knock, the engine is in a no load condition so it would be very unusual to have true detonation at idle.

DAVE00

iTrader: (10)

It does detect knock on startup, but I know that and it's pretty normal. However, it's picking it up at idle when she's hot and when I come to a stop at a light or sign the car will go from zero knock to knock and pulling upto 12 deg.

Big Al

iTrader: (1)

When I had this it was the alternator tapping the valve cover. You could not hear it. The long bolt was loose.

Al 95 Z28

DAVE00

iTrader: (10)

Damn, I'm going to check that as I loosened that bolt up the other day to swing the alt away from the VC when I pulled it to check the rockers. I know I forgot to tighten it down, so that could be the culprit. We'll see.

If not, I'm going to pick up some 100 octane to see if this is truly false knock.

DAVE00

iTrader: (10)

BTW - Were you running Stock VCs?

wrd1972

iTrader: (12)

I have come to the conclusion that the parts store KS might have been bad. I OHMd it and it was the same as another aftermarket I had in the tool box. I installed the second one and the random KR is far far less. I also did not use teflon tape on the threads but I am not sure if that made a difference. I think I got some questionable gas and it was just bad enough to make a suspect KS freak out.

Big Al

iTrader: (1)

To check the knock sensor, put your DVM on AC volts and tap the sensor. You should see a jump from zero. Don't hit the sensor too hard or you'll kill it.

Al