Guys,

As most of you know I've been chasing some false knock issues on my car. I have removed the delteq ignition and gone back to stock with a MSD blaster coil and the car seems to run much smoother, however my PCM is still picking up knock (only at idle -950 rpm -1500rpm) and pulling upto 12 deg timing. Here's what I've checked:

KS (new and properly tq'd added some tef tape later to try and desentize it as well)nothing loose - motor mounts, exhaust, alternator, etc...
y pipe and headers not hitting anything (clear of everything)
no loose rockers
LT4 KM installed for several years
ZERO exhaust leaks from CAT forward
ZERO vaccum leaks
Still present with 100+ octane
Injectors flow checked and cleaned
Fuel pressure fine and new pump

The weird part is the PCM won't pickup false knock until the car is warmed up and goes into closed loop. Once that happens the PCM will randomly pick up knock and pull upto 12 deg timing and you can feel the car changing timing and then it will go away and come again randomly. One other thing, is using DataMaster to log the car I am getting "DATA ERR" flashing erratically in the "DATA OK" status indicator up top. I have read this is usally due to noise in the line from a bad gound but all my grounds check out perfectly. Could this be an indication that my PCM has issues? I am trying to see if they two may be linked some how, as I have been chasing this one like crazy.

 

Cloosed loop only??? Think maybe it has a lean condition in that area?

 

The BLM's are in check around 128-135 (split due to my large LSA at 108). Give a little gas and BLM's level out.

O2s are new and fluctuating fine.

 

Anyone?

 

Are you using a Scanmaster on the car as well? They are known to give Datamaster issues when both are trying to read signals from the PCM.

 

Nope, just TTS Datamaster for reading and Tunercat for Flashing. I'm going t be checking all my grounds again this weekend and also the ALDL port ground and com cable.

 

Does your SES light work?

 

Yes, it lights up normally during cycle on. No DTC codes are being thrown when scanning it.

 

To see if it's entire related to going into closed loop try this. Confirm closed loop operation and pulling timing. Shut off the engine and then restart it. For a few moments, it will be in open loop until it gets to closed loop. See if the same thing happens to the timing.