Thread: Knock Retard when accelerating

I've been trying to trace down the cause for a while now, and it wouldn't be that big of a deal if I weren't getting at least 1.9* of KR whenever accelerating. At Idle, if I give it gas I will get a vibration in the 1100-1200 RPM range and the scanner will occasionally show some misfires mostly in cylinder 4. I've changed the plugs, wires, fuel injectors, and sprayed for vacuum leaks without any success. I am running a stock pulley, and have no engine codes.

Mostly Stock...CAI, U-bend, delete, AP605 Spark plugs, aftermarket mufflers, and DHP v1.0 PCM

1.9* of KR is during normal driving/acceleration, it can get up to 5.6* at WOT. I scanned with EFI Live which uses it's own propriatary format. But here is s snippet, one at idle...one at a brief WOT run.

IDLE
RPM:734
o2 #1: .807v
o2 #2: .009v
SPARK Deg: 27
KR: 0
INJDC1: 4.777
INJDC2: 4.777
AFR: .5
MAF: .98 lbs/min
ECT: 196
IAT: 154
LONGFT1: -2.3
LONGFT2: -98.4

WOT
RPM: 4585
o2 #1: .924
o2 #2: .017
SPARK Deg: 7.0
KR Deg: 5.6
INJDC1: 59.705
INJDC2: 59.705
AFR: 1.00
MAF: 21.91 Lbs/Min
ECT: 196
IAT: 147
LONGFT1: -0.8
LONGFT2: -96.9

I'm personally leaning towards bad o2 sensor, or maybe even a bad cat.

lol......................

Scan
72909WOT from xxmattfxx -- Scan Depot dot net
...sorry it's all over the place

ttt

Haven't made a whole lot of progress on this issue but I have done quite a few more tests.

-Injectors Replaced (was an occasional few misfires at idle)
-Upper Radiator supports replaced (rubber had cracks in them, suspected false knock)
-Spark Plugs and Wires Replaced (again, misfires at idle)
-LTFTs close to zero
-230 degrees at the inlet and outlet of the catalytic converter. (no other indication of a bad cat...smell, glowing, lack of exhaust)
-Fuel Pressure within spec. (idle spec)
-No Trouble codes
-Front O2 sensor replaced

I'm not quite sure where this KR is coming from, I have stock pulley and all other performance related mods are more, restriction reducers...Cold air intake, U-Bend Delete, Magnaflow mufflers.

What I am seeing now seems to vary with the weather and the temp of the engine. Taking a simple drive to work, or a friend's house I'll look down at the max KR and see something near 5 degrees. On the highway in higher speeds, I'll see KR fluttering around a consistent 1-2 degrees even with cruise control on.

There are other things that are possible culprits that I could throw money at, but I'd rather have some guidance based on my conditions and save a couple bucks.

are you running premium? haha

always have

I chose "Gen III LS1 99-08 PCM", but if I recall I've used others without much trouble, haven't done anything special...it just works.