2008 Tahoe STILL has misfire. Please send help

[Chloe Golmon]

Hey Y'all,

March 2020 we installed a new motor and ECM ($3500) in our 2008 Tahoe LTZ 5.3.

Took it to the dealership to have the computer programmed and they also changed an actuator in the transmission. (Got locked into park while it sat during motor install) ($2100)

Dealership also told us it had bad gas, and it would run great after we swap it out. (I call B.S. on that )

Brought the truck home Friday, siphoned the gas and it is STILL MISFIRING and having irratic electrical issues!!

We have replaced:
Motor
ECM
ALL Spark plugs
Battery
Negative battery cable
Added an extra ground from motor to frame
Siphoned gas and replaced with new

Remaining symptoms:
That damn Stabilitrak service light is still on
The gauges are freaking out
Nav screen may or may not work
Passenger running boards wont drop
There is still a shake in the motor
Running codes P0315, C0561

Background:

Fall 2018 took our 2008 Tahoe LTZ 5.3 to the shop for a serious shake while driving. They said it was lifters. $2400 later, lifters were replaced and the truck was still shaking. We were told it was cylinder damage from dricingnwith a misfire and we had to get a new motor. Mechanic literally told us to drive it til it died there was nothing else to do....

We did just that (stupid decision, considering recent research. I'm still smh about it) October 2019 it finally died. We have replaced everything we can think to fix.

Y'all. PLEASE HELP US figure out what else we could possible replace to save this truck. We are $8000 into it on top of our note and it kills me to think of giving up now.

Thanks

 

[kbuskill]

Hey Y'all,

March 2020 we installed a new motor and ECM ($3500) in our 2008 Tahoe LTZ 5.3.

Took it to the dealership to have the computer programmed and they also changed an actuator in the transmission. (Got locked into park while it sat during motor install) ($2100)

Dealership also told us it had bad gas, and it would run great after we swap it out. (I call B.S. on that )

Brought the truck home Friday, siphoned the gas and it is STILL MISFIRING and having irratic electrical issues!!

We have replaced:
Motor
ECM
ALL Spark plugs
Battery
Negative battery cable
Added an extra ground from motor to frame
Siphoned gas and replaced with new

Remaining symptoms:
That damn Stabilitrak service light is still on
The gauges are freaking out
Nav screen may or may not work
Passenger running boards wont drop
There is still a shake in the motor
Running codes P0315, C0561

Background:

Fall 2018 took our 2008 Tahoe LTZ 5.3 to the shop for a serious shake while driving. They said it was lifters. $2400 later, lifters were replaced and the truck was still shaking. We were told it was cylinder damage from dricingnwith a misfire and we had to get a new motor. Mechanic literally told us to drive it til it died there was nothing else to do....

We did just that (stupid decision, considering recent research. I'm still smh about it) October 2019 it finally died. We have replaced everything we can think to fix.

Y'all. PLEASE HELP US figure out what else we could possible replace to save this truck. We are $8000 into it on top of our note and it kills me to think of giving up now.

Thanks

Some more info would be great...

Who installed the engine?

Was it new or used?

Did you also replace the positive cable and clean all connections?

Any other information that might be pertinent?

From the codes it sounds like the crank position sensor needs to either be replaced and relearned or at very least relearned.

The other code is just telling you your traction control system is disabled. That should go away after you get the truck running correctly.

Any time there is a misfire the truck will automatically disable the traction control system as well as the stabilitrac system to rule those out as possible culp6for the misfires.

 

[Chloe Golmon]

Kbuskill

Remanufactured motor from Powertrain, 3 year warranty. My husband and his brother put it in (not their first motor swap). We literally had 2 shops refuse to do the work because of the year model of the truck .

Have not replaced or or cleaned the positive cable. We haven't taken it past idle yet, we don't want to damage anything in the new motor that would kill the warranty.

 

[Chloe Golmon]

Kbuskill. Also the stabilitrac service light is how it all started in 2018. We got stuck in the sand at the beach. After the rocking and rolling of getting out, the stabilitrack went out somehow and everything else went to hell following that one event.

 

[swathdiver]

Kbuskill

Remanufactured motor from Powertrain, 3 year warranty. My husband and his brother put it in (not their first motor swap). We literally had 2 shops refuse to do the work because of the year model of the truck .

Have not replaced or or cleaned the positive cable. We haven't taken it past idle yet, we don't want to damage anything in the new motor that would kill the warranty.

Was the engine complete or did you have to swap over the intake manifold and VLOM and throttle body and such?

Do you guys have a Tech-2 or an advanced scan tool? It will pay for itself in just helping you guys figure out quickly and correctly what's wrong. If you guys are in Florida near me I'd be happy to put mine on it.

 

[Chloe Golmon]

Swathdiver, we're in Texas. Thank you though! We've been using a Bosch scanner, my Brother in Law has a better tool we can grab from him.

The VLOM is new, throttle body and intake manifold are both old. I 've seen some videos where they might need to be cleaned, is that what you're thinking?

 

[swathdiver]

Swathdiver, we're in Texas. Thank you though! We've been using a Bosch scanner, my Brother in Law has a better tool we can grab from him.

The VLOM is new, throttle body and intake manifold are both old. I 've seen some videos where they might need to be cleaned, is that what you're thinking?

Well, they may need cleaning but that usually wouldn't the source of the maladies you're experiencing. I would get hold of that Bosch scan tool and have a look, if its a bi-directional tool that can run tests and relearns and such, you'll quickly identify the problem. My Texas vacation keeps getting cancelled! Have no idea when or if we'll get out there now this year.

 

[Chloe Golmon]

If it still isn't driving, you're welcome to come by lol. I LOVE my truck, that's why we went down the rabbit hole of trying to fix it instead of unloading it.

I dont understand how 4 different mechanics at this point (including the dealership) haven't been able to diagnose this. Especially considering this happens in a LOT of 3rd gen Tahoe's. Pulling our hair out over here.

 

[Chloe Golmon]

Notes on the ticket from the dealership:
"Reprogram ecm vehicle started but ran bad clean plugs remove intake and repair ground but vehicle was still missing at number 4 cylinder. Did fuel service - gas in tank could be bad vehicle do need a fuse box it is bad"

Plan to change out the fuse box, and take it to relearn the crankshaft position sensor,clean positive cable.....we'll see what happens

 

[Peter Tremonti]

This may be a stupid question, but since it wasn't mentioned I'll ask. Did you try swapping plug wires and coils around to see if the misfire moves? Have you done a compression test? I know it's a new engine, but that doesn't mean it wasn't built on a Friday at quitting time. Just sayin'.