Strang Knock Problem

[yukondoit]

Ok here goes.
When im crusing at 25-30 percent throttle, at around 2500-3000 rpms in 3rd gear or OD, A/T. i get knock like crazy, i can see it on my guage. I dont understand i've tried adding fuel up o 5 % and leaning out to -5%. and no change. if i let off the throttle a bit or add it goes away. i believe it was doing this before and was part of my fuel cut problem but I couldn't see it.

Also this around 10 psi of boost, this right where it spools up.

 

[project_tsi]

Its Phantom Knock, Its not "real" knock. If you don't have one, I'd invest in a eprom ecu and custom chip with PK elim code.

 

[yukondoit]

ok, would there be any way to prove its phantom knock?

it seamed to very with the fuel i got but this morning i tested it on my to work and it didnt knock. i was thinking heat soak since the motor was cooler and i should try runing a step cooler plugs.

 

[GVR4592]

ok, would there be any way to prove its phantom knock?

Yes, drain your fuel tank add few gallons of 100+octane race fuel, and datalog again. If you still get the knock it's not real.

 

[yukondoit]

i was actually thinking of doing that.

 

[Dred]

Check the knock sensor as well, make sure it's torqued properly and isn't leaking black gooey stuff.

 

[MrBoxx]

I'll agree with project_tsi on the phantom knock diagnosis. This sounds very similar to an issue I was having. With DSMLink, I have my stock boost gauge set to show knock, and the DSMLink code itself flashes the CEL when more than 5* of timing is taken out due to knock. I'd notice that at around 17-25% throttle between 2200 and 3400 rpm, the boost gauge needle would rise and peg, and the CEL would flash on. This occurred anywhere from 15 in/Hg to 7 in/Hg vac. I recreated the event with DSMLink datalogging it and it showed 12.7 degrees of knock retard (DSMLink doesn't show counts of knock, but I think it may have been the "43" count that is consistent with PK) under these conditions.

The fix was to disable the knock sensor below 3500 rpms. I haven't had the issue since and the datalogs are showing normal knock readings, less than 1 degree, at higher rpms. Since you have a 95 DSM, DSMLink is probbably an option for you if you have an Eprom ECU, or you could get a chip with a PK elimination code, as project_tsi mentioned.