So I have had false knock show up on my scanmaster since I installed it a few years ago. I have ran 100 octane fuel in it and played with the timing on the dyno with no avail. I'm at about 36º of timing so I don't think that's the problem. My dyno tuner wanted to tune it out but with the new motor going in next year, I'd rather keep it. I'll probably just put a resistor in on a switch so I can turn it on and off.

I've got a LT4 Knock Module and I think we already desensitized it. What could be causing this? The valvetrain is stock, I've got long tube headers and ploy motor/tranny mounts. Also will the scanmaster work with a LSx pcm/harness swap?

 

Have you tried replacing the knock sensor yet?
I fixed a false knock issue on my friends LT1 with a new sensor.

 

That was about the 3rd thing I did. I also made sure the KS wire wasn't running next to any high voltage wires. I don't know what else it could be.

 

Under what conditions is the knock showing? WOT? all the time? certain RPM's? lugging the motor? Bumpy roads (rattling exhaust?)

 

It doesn't seem to be regular. I don't think it has ever showed up at idle. It didn't seem to do it on high speed WOT runs, although I wasn't really watching the scanmaster, but it didn't record any so I'd assume there was none at 70+mph. It seems to come easier when the torque converter is locked, but sometimes I can't get any at all.

Sometimes it seems like if I try to get it to show up while the car isn't in closed loop yet it will show up easier, even when it has gone into closed loop. But if I'm easy on it until it goes into closed loop, it's harder to get it to show up. But its still completely random and seems to have a mind of its own. I try to recreate it to see if I can pinpoint where its coming from, but its just too random.

 

My car had some raondom KR here an there when it would shift or chop the throttle or at certain rpm's or whatever. Can you datalog a pull and watch the timing and see if any is really being pulled?

 

Have you tried the LT4 knock module? That was a fix on the LT1 powered Caprice/Impala when guys went with lumpier cams and headers that would sometimes show up as false knocks- cheap enough part, if they are still there- google it-

 

Have you checked the motor mounts, particularly the one on the passenger side? With it being right next to the knock sensor, a rattle there would cause knock retard.

 

Yeah, we just had them off a few weekends ago to put in the new k-member. We got everything torqued back down so I'm pretty sure it not that. I can't hear any unusual tapping or anything so I have no idea where its coming from.

 

i had a knock problem for years that i figured out and fixed. you have to massage the burst knock tables. some are in the constants and some are in the regular spot. look at you're datalog where you are getting knock then correlate it to the burst knock tables and make the necessary adjustments.

 

lets look at who's having false knock problems and who isnt.

I for one never get false knock and have what I consider a perfect candidate for it.

I also have a 1996 knock sensor from the stock OBDII car and a 1995 OBDI PCM with the "resistor mod" inside the PCM across the knock sensor wire pins.

My knock sensor tables in the PCM are stock, and the only time I get knock is when I think it's real (30+ degrees of timing with 92 octane with 6+psi boost). When im in the 25 degree area of timing I dont have knock at all, so far up to 10psi, no knock, 25degrees ish timing.

Just thought I'd throw it out there, see if many "resistor mod" people are having problems.

I would think the resistors effectively de-sensitize the signal/sound (while bringing the resistance in check with what the PCM thinks is normal) since the knock sensor is basically just a microphone.

Also, if I split my bock in half from detonation/knock that went undetected I'll definately let you know, but so far it seems like it's working just fine.