Sudden KR Whats going on?

[DRTWRK]

I have recently developed significant KR in the lower RPM ranges. It is more prevalent as you reduce engine speed towards idle and during low RPM’s. While accelerating or steady cruise everything seems fine. My tune is 2Bar OLSD, Further, look at my (4-29-09 1kr.hpl) scan, VE LTFT’s. I have my LTFT’s fuel trims switched off in my tune but now see readings in LTFT’s of -100's. The STFT’s still read 0’s as always. I made a 2nd scan (4-29-09 2kr.hpl) within a few minutes after the first and this time my LTFT’s read 0’s as normal. Problem is I never changed anything.

I have not changed anything lately and have no idea of what is going on with this erratic behavior. Can someone take a look at my scan? I also will include my latest tune.

[roberttimmons]

I would take some timing out in the midrange.. Have you tried resetting your fuel trims? Iv only seen -100 fuel trims in cars that have too many things logging at the same time. Give me a few I will poke aroudn in your tune..

[DRTWRK]

Additional scans revealed LTFT's back to the normal 0's reading. That must have been a fluke.
I reducing timing as much as 10* throughout the affected rpm range and still found substantial KR with seemingly no effect. Again mostly in the lower rpm ranges below 2400. While accelerating and or in boost, I get NO knock retard. I do not hear any strange sounds from the engine.

[DRTWRK]

Any one else have any ideas?
KR getting worse at low rpm's but still no audible sounds or knocking.

[Stalker L-67]

If it is false knock and its getting worse, check for something coming loose and rattling against the engine. At least this has solved the problem in other cases.

[DRTWRK]

Is it possible the sensors could pick up anything in the torque converter or transmission to cause KR ?
My heavy duty truck mechanics seem to think they hear some sort of rattle in the torque converter area after removing dust cover.

[blownbluez06]

I've seen loose bolts on the converter and cracked flywheels make knock sensors go nuts in older cars. I don't have any experience with the newer cars regarding that though.

[turbo 6l]

just my thoughts on this but it does not look like you have a 2 bar tune on this and it also maybe maxing out the stock map when you accelerate or decelerate i say this because you no offset on the map sensor under engine diag /airflow/ map . i am not a expert on tuning but just went through this with my truck hth brett

[DRTWRK]

turbo 6l
You may not be able to read the .hpt file with your version. I do have a 2bar MAP and a 2bar OS. 193-200+ MAP readings dependent on weather & outside temps.
I dont think the tune is why I am getting this low rpm KR readings.

It may have been the "cause" as it comes and goes and I have yet to find the source. I have found after I run up the RPM range a few times both in boost and or non boost, the "ticking" is more prevelant. After a few miles of normal driving the sound slowly diminishes.

[turbo 6l]

try to copy your low octane to high octane and see if that helps make your octane look alike see if that slows down knock retard

[DRTWRK]

I have lowered timing as much as 10* in the problem areas with no reduction in KR

[turbo 6l]

also if you are running map sensor part#12580698 the correct # for linear
207.66 and 9 for the offset.. sorry for not upgrading my version i did it today and now i can see . i did a search for gm 2 bar linear and offset values for map 12580698 hth brett

[turbo 6l]

maybe you can try my spark tables in your tune . do not try too load my tune i do not have a drive by wire . i have a small turbo t-62 on my with no intercooler
at 10lb of boost no spark retard 90 degree day in texas on 93 octane . you may want to add a couple of degrees 400 to 800 rpm/15 cyl air to 40 cyl air

[turbo 6l]

by the way my truck is stock other than turbo

[turbo 6l]

my truck is a 2000 2500 4wd with a 6.0 maybe this will help i do not know

[turbo 6l]

looks like the timing is coming from idle spark advance tables in drive / in park

[DRTWRK]

Thanks turbo 6l
I have been running near this same tune for months without KR problems . It seemed to have started recently and without other symptons. I drive the truck daily and would have thought if something was going bad it would get worse before getting better. So far nothing, I have tuned the KR nearly out in the problem areas where its not pulling timing but realizing this is not a fix.