Issues with 2008 Burb

[matt72991]

alright so im new here trying to learn. i have a 2008 suburban 2500 with the 6.0l and 6 speed trans. i have NOT done any tune modifications yet. trying to get it running right, (thats why i bought HP tuners). the truck isnt trowing any codes but its running like ass. attached is the latest log i did. i see it has a bunch of Knock Retard and pulling tons of timing. if someone could point me in a direction of what to look at, please do!!

things if done.
put Premium fuel in
replaced TPS and MAF
new spark plugs
new spark plug wires
checked for vacuum leaks at the intake manifold-holds 20 in lbs of vacuum at idle
checked intake for leaks at all connections.
replaced cats due to them glowing after driving home at night. thought they were plugged. new cats made zero change.
had truck scanned with multi thousand dollar Mac Tools scanner. that showed no codes related to the issue.

i am at a loss as to why it is showing so much KR and pulling so much timing. could it just be that the knock sensors are bad and giving bad information??

thanks Matt

[5FDP]

Maybe it's the knock sensors, hard to say.

How are the motor mounts? I've seen busted up motor mounts cause lots of extra vibrations.

[matt72991]

They appear to be brand new. They are nice and black and everything else around them is a dirty sand/rust/dirt color.

[blindsquirrel]

Man, that's weird. The KR just comes and goes apparently unrelated to anything else that's happening. Also goes open loop for long stretches, independent of the KR weirdness.

What was the weather like during those logs? IAT never changes from 66-68* the whole time, in both logs.

Possible the muffler is plugged up or some other restriction downstream?

[matt72991]

Man, that's weird. The KR just comes and goes apparently unrelated to anything else that's happening. Also goes open loop for long stretches, independent of the KR weirdness.

What was the weather like during those logs? IAT never changes from 66-68* the whole time, in both logs.

Possible the muffler is plugged up or some other restriction downstream?

that temp sounds about right for the night i took the log. i took another a little bit ago after replacing the intake gaskets cause i thought the knock sensors were under the intake. found out i was very wrong and they are on the side of the block.. but same issue. but the intake temp was at 73 which was the around the temp for me here in Norfolk VA.

for the exhaust, ill disconnect the rear half and drive it adn see if i get the same thing.

[matt72991]

well i just figured out the problem. i went to replace the knock sensors and found the wiring to the driver side sensor had been cut and butt connected back together!! cut those out and soldered and heat shrunk the 2 wires. also put the new sensors on. attached is the latest log. only saw a couple of degrees of knock retard throughout the log. which ive read is normal on a stock tune.

now on to learning to tune. thanks for the help.

[blindsquirrel]

Cool. Run better?

One thing to think about, if you don't know how old the O2 sensors are I'd put fresh ones in it before investing a lot of time tuning. O2s are wear items and get tired after a while, even if their data looks OK. In the log there are a few spots where they are switching the same but most of the time the B1 seems much faster to react (switching more often).

[matt72991]

oh wow alright i see what youre saying about the 02's. i hadnt noticed that. i will prolly order those before long. gotta a few other little things to fix up first.


but yes the truck is running lightyears better!! its actually drivable. it was so bad, you couldnt drive it. it had no power to pull out and accelerate.