did you tell him you have read ls1tech? He would have listened than

This might be why Chris (service manager) went and got him personally to meet me in service drive. Chris looks out or me.

I'm not too smart on the electronic side of things, but can a PCM differentiate between "false" & "real" knock? How does the PCM know the difference between the two?

he is saying that knock in general should not cause a misfire. i dont feel that even if it did cause a misfire that it would single out one cylinder to misfire being that the ignition isnt controlled individually per cyl

exactly what i meant, the tech is claiming the headers are causing false knock, which i'm ASSuming he is blaming the false knock for the cylinder #8 misfire...... which isnt possible.

if its picking up false knock (like alot of GMs do anyways) then it would simply pull timing, not cause a noticeable misfire above XXXX rpm, loss of power, but definately not a SINGLE cylinder misfire.

even real knock (detonation or pre-ignition) shouldnt theoretically cause a misfire either, so using knock as the cause of a misfire is in my opinion a cop out (or just an uneducated technician) which in this case doesnt seem to be the case.

PAPABEAR, since it seems to be related to RPM i'd imagine its valvetrain related, but thats just an educated guess.

my question would be does it seem to be more noticeable in higher/lower gears, when the engine is cold/hot, and when did it start.....

a knock sensor will not cause one single cylinder to pull timing, this is a gm system not a big stuff 3, dont feel bad about the HHR, when i took my tbss in for work they gave me an aveo

it does it hot and cold an above 4000 rpm and in every gear.

I Forgot to add that he brought up my motor mounts. He said I could have a mount bad that is causing the header to e too close to frame rail.

This is the stuff I'm talking about. That just doesn't make sense to me. Really grabbing for things at this point instead of diggin in. A motor mount on a 3 year old vehicle with 50k miles isn't very common.

I just want my truck back.

Hey hey hey... My Uncle Les is a salesman there and he is no dickface sir.

Les Rogers has sold me 5 vehicles. Great guy. Used to live next door to my uncle Chris.

Les has sold us two. He is the ONLY person I would go to at Hendrick. Great guy.

Papabear why even think about false knock at this point whether its from headers a motor mount or anything else because its not causing your misfire. They do understand that's what you are trying to get fixed right?

Yes they do. I'm not worried.

I am actually looking forward to saying I TOLD U SO!

Diamond in the rough :).

I hate little quirks like that. Knock sensor can be a little tricky and pick up some intrerferance from time to time. But when they are activated it should pull timing and reduce some power not pop and misfire. JP might be the guy to help you, log some pulls turn some stuff on and off should help you isolate the problem.

I'm not paying Jamie $375 to tune my truck, sorry. This will be figured out by the dealer. All I know about knock sensors after all this and all the reading I've done is that I don't know shit about them!

Have you tried to isolate the latest mods you installed and slowly determine if any of them is causing this? i.e. plug wires and all?

heres another thing to think about, what if it actually is knocking? cylinders 7 and 8 are prone to it b/c they usually run about 20-30* hotter than the rest. why dont you just pull a valve cover off and see if the spring is broke?

Did they decide the injector wasn't causing it? If its not an injector then its most likely a valvetrain issue

it could be as deep of a problem as the reluctor wheel on the crank or cam having a small nick in it. start with the simple stuff instead of letting it sit at the dealership for days, i promise your truck is the least of their worries when they have easier money coming through the door. go get it back and swap the coil pack with another, swap the injector with another, pull the valve spring out and ckeck it, make sure the rocker is torqued down properly, make sure the pushrod isnt bent, swap the wires and plugs. thats a lot of simple stuff you could do yourself that doesnt take much time

I've already done all the simple stuff. Remember my other thread? Re read my first post. I have swapped EVERYTHING and done everything short of pulling the valve cover.

I have ruled out injector, plug, wire, coil pack, and tune.