I installed an LE2 setup this summer along with a PCMforless tune from Bryan Herter for 91 Octane. My problem is that I am getting false knock readings and cannot find the source. I'd like to find it before bypassing the system. New GM engine mounts were installed with the heads/cam. I've checked the exhaust for frame contact/leaks, readjusted the rockers, checked all bolts on engine for something loose..no luck! I run the impala 0.029" gaskets with Autolite 104's.

Running 94 Octane, the knock with an LT4 module is pretty much all the time, pulling from 0 to 5 deg of timing, more prevalent on 100% throttle, but also at idle & cruise following TPS position (engine load). The stock LT1 module surprisingly produces MUCH better results, but still picking up knock on 100% throttle over about 3k rpm. The timing pulled is immediate at gear change and 100% throttle (to 5 deg), then progressively less (to 1 deg) at 6300 shift point. None at idle or cruise.
I have:
1) replaced the Knock sensor which seemed to help
2) tried both stock and LT4 modules - stock is much better
3) run 110 octane with similar results (no less knock)
4) run 91 octane with no audible knock

I have datalogs with datamaster. If anyone wants to look at them, I can email them. The car seems to be making good power and really hauls even with the screwed up timing. If I bypass the knock sensor, all is 100% ok as expected and there is no audible detonation.

Anybody come accross something similar?
What can I do here besides bypassing all together?

 

If running 110 didn't produce results and you aren't seeing anything on your scans indicating you are lean I'd start looking elsewhere. It is more than likely hardware related. Lifters new? Preload? NSA rockers? Which guideplates? What springs are you running? Also check your wiring for melting!

 

I have new GM LS7 lifters with 3/8 turn preload, NSA 1.6 Comp's with GM guideplates, and PAC1218's.
By wiring you mean the wiring to the knock sensor itself from the PCM?

 

The GM guideplates sometimes rub. Look in the groove of the guideplate to see if the pushrod is hitting it. I cant remember the guy that found this issue but he posted about doing 1.7 RRs with GMPP guideplates and he was getting knock from that and they were making racket. That very well COULD be your issue. Also the wiring im talking about is the knock sensor to the PCM. Sometimes that wiring bundle can get burned on headers and cause weird issues.

 

Thanks, I'll pull the covers off this weekend and double check the guide plates and replace the wire for some testing..

Any body have any other thoughts?