Knock sensor or dealer copout?

[PapaBear]

Originally Posted by Matts94Z28

The Pushrod can be check in less than an hour if you know what you are doing. If you need help pulling them, let me know. I can give you a hand if you need it. I also have some extra push rods from a 6.0 I had. If it is in fact the issue, I can give you a new set.

I also have some stock lifters.

Thanks, Matt. Hopefully I don't have to go this route, but if I do, I appreciate the offer immensely. I can pay you in beer and food, maybe some cash if the financial department (wife) agrees. But I assure you, she is tired of this already.

[PapaBear]

Here's what the dealer "invoice" says:

Heard no engine nooise, engine and valvetrain are quiet. 8 DTC's. 6 O2 DTCs as rear sensors are missing. P0300 and P1482. Diagnosed P1482 and found that customer had spliced into cooling fan signal wire from ECM. Reconnected wire and still cannot command fan. ECM may have been damaged due to splicing. Vehicle is equipped with full length headers without catalytic converters, aftermarket exhaust system, cold air induction system w/ relocated IAT. Modified transmission with 3200 RPM stall converter. Test drove vehicle with customer and took snapshot of IGN data showing knock at hard accel. found tha tpassenger side header and Y-pipe are contacting the frame. Provided clearance for header per customer direction and took another snapshot. no knock detected, but still breaks up at high RPM. Customer has NGK plugs installed. Replaced plugs and wires. Performed static and running compressoin checks as well as cylinder leakdown with all values good. Removed valve cover and checked springs, rockers, and pushrods: GOOD. Checked fuel pressure and vacuum at WOT: GOOD. No fluctuation in vacuum gauge . Removed fuel rail to check for contaminants / debris : good. Checked injector pulse to injectors: GOOD. Took fuel sample and checked ethanol content: 10.4% - GOOD.
NOTE = 195 psi static compression
90-93 psi running compression
2-3% leakdown.
SVC manager spoke with GM(general manager) and we respectfully decline to continue any further diagnosis and/or repairs on this vehicle. Customer is not being charged for any services, vehicle put back to same condition as when it arrived.

I never told them about the trans/converter, they must have gathered that intel from this forum.

[Matts94Z28]

You know what. This all makes since now...

Rick, the GM is a POS. He is a worthless person who does not car about any individual other than himself. He has abused just about every employee verbally, including Chris, and has actually laid hands on two employees in the past 4 years he has been at Hendrick. How he is still the GM, I do not know.

I wouldn't be surprised if he forced Chris to get your TBSS out of the shop. I have seen some shady stuff go on at that dealership due to his management.


PRINT THAT OUT!

[2001hawk]

Sucks to hear that they aren't going to be fixing your truck. However like someone said if the scanner doesn't tell them what to replace then they are going to throw parts at it until they get lucky or tired of messing with it. For the most part the techs think if you brought it to them then they know more than you and you should shut up and let them spin some BS to sound like they can diagnose anything. Most techs at dealerships end up asking for more money per billable hour which then in turn they are given jobs that they can't possibly finish in the alloted time and by the time they get done they have actually made less money each day.

[MonteC]

Originally Posted by schardbody

they want no part of the truck anymore because they are worried about public humiliation when they cant figure out the problem......

like someone else said if the computer doesnt spit out a specific problem that localized to a very common problem then they are stumped.

the VERY second thing done should have been a compression and leakdown test, while its likely it'll come back in spec it would atleast rule out a few things.

they wouldnt be able to diagnose a valvespring issue unless its obviously broken, my opinion is its likely just weak.

a bent pushrod would cause less power from that cylinder which would show up as a misfire (cylinder contribution) but i've never seen an LS bend a pushrod even when being over revved.

a lifter is another possible cause but you really wont know much without pulling the head and swapping them since its a higher RPM issue they/it is probably going to appear fine to the eye just like the valve spring....


be glad they decided to send you packing, they never would have figured it out and you'd have a truck that was part swapped until they were fed up, because throwing parts at a problem is all they are capable of, even with all the technical support and equipment they are still incompetent....

I had two bent out of one engine. Bone stock.

[schardbody]

Originally Posted by MonteC

I had two bent out of one engine. Bone stock.

what caused them to bend? not trying to say it doesnt happen just saying i've never cured a driveability issue on an LS based engine by replacing bent push rods...

[MonteC]

Originally Posted by schardbody

what caused them to bend? not trying to say it doesnt happen just saying i've never cured a driveability issue on an LS based engine by replacing bent push rods...

I have no idea. I bought the motor with 89k miles on it out of a fbody parts dealer. Put it in my monte carlo and pulled the valve covers to change springs and found two bent pushrods. Was attached to a six speed if that makes any difference.

[98Camarod]

Probably an over rev missing a shift or a messed up down shift

[MonteC]

Originally Posted by 98Camarod

Probably an over rev missing a shift or a messed up down shift

Thats the conclusion we came to as well.