: LS2 low RPM knock

07-21-08, 04:26 PM
Since I got my car (used @ 25K miles) I have had an issue with low-RPM knock. I am seeing a consistant amount of knock retard in the 1400-2000 RPM range. I did a top engine clean with Seafoam and I also swapped the plugs with the same plugs I run in my Vette (NGK TR55ix's). It seemed to help a little, but it's still there.

It seems like anything above 40% throttle in that RPM range causes knock retard, even if I slowly roll into the throttle. Once it gets above 2K RPM it seems to go away (ie, flooring it at 2400 RPM I don't get knock). The bad thing is, that knock retard takes a while to bleed off, and in turn carries will into the upper RPM's. I won't even be able to get a good baseline dyno at this point.

With the exception of the plugs, this is a stock V.....for now. :rolleyes:

I guess my question is, are the LS2's that sensitve to knock? Before I start adjusting the spark tables, I wanted to make sure something else isn't going on.


07-21-08, 04:31 PM
I haven't dealt with that before in my LS2. Maybe this thread will be helpful? http://www.cadillacforums.com/forums/cadillac-cts-v-series-forum-2004/145034-c6-engine-tapping-noise.html

07-21-08, 04:37 PM
What type of fuel and brand? Have toy logged and seen a tempature relation? :)


07-21-08, 04:46 PM
Wow, I was going to go back and edit the original message, but there were already responses! That's service! :cool:

I meant to say this is not audible ping, but ping picked up by EFILive. Maybe I'm crazy, but I sware I can also 'feel' it in the car a little as the throttle response gets a little 'lurchy' when I roll into the throttle. It's ever so slight, and maybe it's unrelated.

As for temp, etc...it's been doing this since I bought the car (early Spring), so it's not gas or temp related.

Thanks again guys!

07-21-08, 04:58 PM
It might be the fact that you lugging the motor. What gear are you in and speed are you going when in starts to knock?

07-21-08, 05:01 PM
Another thing to check is bad mounts. In my turbo buick, if the motor mount went out or you had your motor touching something else it would cause false knock and retard the timing. Do you have headers? Is your exhaust touching anything?

07-21-08, 09:12 PM
Has it had a K&N filter in its life? If so, clean the MAF.

Since the V was purchased used, are you 100% certain the PCM is stock?

07-22-08, 12:45 AM
The LS2 has aggressive KR sensors due to a high compression. Depending on your climate, and quality of fuel, you may be able to get away with making them less sensitive a bit.

07-22-08, 01:53 AM
What is the milage on the vehicle as of today?

Have you at any time put in injector cleaner?

Have you resetted the PCM by disconnecting the negative line on the batt?

If you take off the TB do you see oily residue?

Is your MAF clean?

Is your MAP clean?

Are all the wires going to the sensors clean and free of "Chard" sections?