89LS1FOXER

iTrader: (47)

Need help and or ideas, thanks in advance!! Working on a friends Silverado with a false knock issue or a real knock we cant track down or hear... his setup consist of:

-01 ECSB Silverado
-01 5.3 stock short block (came from known good running donor)
-LS6 oil pump and JP double roller chain
-Speed inc. TU2 cam, TSP dual springs
-shaved 243 heads and LS9 gaskets with ARP bolts
-Trick performance 78mm turbo kit
-full 4wd 4l80e conversion
-maybe good? used (off of here) rev maxx 3600 converter

Its running on a 2 bar SD tune, tuned by us with help from Zippy with Zippy performance, truck is getting knock bad under load (even light load) while in gear from 1500 rpm's on up.... will not show knock in park/neutral at same rpm's ever? Can not hear any noticeable knocking even with stethoscope on any part of engine or trans, normal dual spring clatter, knock sensors are brand new GM torqued to spec with new harness, all wiring from connector to ECM has ohm'ed out just fine, knock sensor pins at ECM have good tension. We have installed another set of sensors and harness with the same result. We did mount a set of grounded sensors off to the side of the engine and test drove with no knock what so ever so ECM if definitely picking something up... nothing is rubbing, everything is tight, fresh tank of 91 octane (already drained and re-filled), TR6 plugs gapped at .035, motor/trans mounts look ok.... Only thought we have is a bad Rev maxx converter making an internal noise under load in gear??? Its kind of all that's left? Any idea's would help greatly, Zippy says its not a tuning issue and I have full faith in him! Thanks again JR

hellbents10

iTrader: (10)

Any time you change this much stuff the knock sensors can become a hassle. I would bet on it being false knock, and with Zippy tuning it I would listen to him. He knows these things better then 99.9% if the people on here.

If it where mine they would be off....

89LS1FOXER

iTrader: (47)

Thanks for the input man, I have full faith in Zippy, not questioning his ability what so ever, I do believe he wants to leave the knocks on though..... I'm mainly wondering if anyone has found something to cause this, running out of things to check, going to drop the torque converter off today to get checked out....

Sarg

iTrader: (6)

Correct me if wrong, but knock sensors are tuned to a certain frequency and when you change a ton of parts on the motor that frequency that the knock will have will change as well. How bad is the knock reporting to be?

89LS1FOXER

iTrader: (47)

pulling 10-12 degree's at times.... We have multiple trucks out here with almost the same setup and have not ran in to this issues yet.....

Sarg

iTrader: (6)

Dumb question maybe but have you tried swapping sensors?

89LS1FOXER

iTrader: (47)

yeah its in the text above, swapped sensors/harness and drove with sensors grounded outside of engine as well....

89LS1FOXER

iTrader: (47)

well torque converter checks out ok....

munn79ta

i just had my car dyno tuned last week and had issues with false knock. my exhaust is open downpipe and doesnt go past the engine block. my tuner said that was more than likely causing my false knock. we turned them off and made lots more power. still going strong...

1969x11

iTrader: (36)

411 computer?

89LS1FOXER

iTrader: (47)

was showing knock with and without the full exhaust it has now....

yes I believe so, doesn't have the old black box style if that's what your asking...