P0300, Service stabilitrack and rough idle.

[Joe W]

I’m at a loss.

I have a 2011 Tahoe z71 that we purchased a month ago. Truck has 165k miles. It started running rough at idle and seemed to be getting bad fuel mileage. On cold starts it seems to run great and after warming up it gets a slight rough idle. Seems to lighten up when placed in park or neutral. After leaving in the morning after getting the vehicle to 30mph or so the check engine light will flash for 10 seconds and go away. Also the service stabilitrack will come on but not always. Light stays off for the rest of the commute. When using a scanner the only code I get is P0300. Under misfire data I get random history of misfires on cylinders 2,4,6 and 8. But with the engine running I don’t get a count of any misfires on any cylinders. Idle stays around 520- 560 rpm.

Things I’ve done.
Replace plugs and wires
Replaces cylinder 8 coil (most history of misfire)
Replace number 8 injector (most history of misfire)
Replaced MAF sensor
Cleaned throttle body
Checked intake manifold for leaks (none detected)
Checked grounds.
Ran top end induction cleaner through port on top of intake (AC delco cleaner purchased through GM)

Any ideas on what my issue could be? It doesn’t feel like a dead cylinder. Anyone with similar problems? Any suggestions are welcome.

 

[donjetman]

Since its happening on the passenger side cylinders only, 2-4-6-8, I would suspect a bad coil harness on that side.

 

[RAFJR]

I’m at a loss.

I have a 2011 Tahoe z71 that we purchased a month ago. Truck has 165k miles. It started running rough at idle and seemed to be getting bad fuel mileage. On cold starts it seems to run great and after warming up it gets a slight rough idle. Seems to lighten up when placed in park or neutral. After leaving in the morning after getting the vehicle to 30mph or so the check engine light will flash for 10 seconds and go away. Also the service stabilitrack will come on but not always. Light stays off for the rest of the commute. When using a scanner the only code I get is P0300. Under misfire data I get random history of misfires on cylinders 2,4,6 and 8. But with the engine running I don’t get a count of any misfires on any cylinders. Idle stays around 520- 560 rpm.

Things I’ve done.
Replace plugs and wires
Replaces cylinder 8 coil (most history of misfire)
Replace number 8 injector (most history of misfire)
Replaced MAF sensor
Cleaned throttle body
Checked intake manifold for leaks (none detected)
Checked grounds.
Ran top end induction cleaner through port on top of intake (AC delco cleaner purchased through GM)

Any ideas on what my issue could be? It doesn’t feel like a dead cylinder. Anyone with similar problems? Any suggestions are welcome.

did you get this solved? if so, what was it?

 

[Fless]

did you get this solved? if so, what was it?

Joe W (OP) was last seen: Feb 3, 2020

 

[Mark Gonzalez]

I’m at a loss.

I have a 2011 Tahoe z71 that we purchased a month ago. Truck has 165k miles. It started running rough at idle and seemed to be getting bad fuel mileage. On cold starts it seems to run great and after warming up it gets a slight rough idle. Seems to lighten up when placed in park or neutral. After leaving in the morning after getting the vehicle to 30mph or so the check engine light will flash for 10 seconds and go away. Also the service stabilitrack will come on but not always. Light stays off for the rest of the commute. When using a scanner the only code I get is P0300. Under misfire data I get random history of misfires on cylinders 2,4,6 and 8. But with the engine running I don’t get a count of any misfires on any cylinders. Idle stays around 520- 560 rpm.

Things I’ve done.
Replace plugs and wires
Replaces cylinder 8 coil (most history of misfire)
Replace number 8 injector (most history of misfire)
Replaced MAF sensor
Cleaned throttle body
Checked intake manifold for leaks (none detected)
Checked grounds.
Ran top end induction cleaner through port on top of intake (AC delco cleaner purchased through GM)

Any ideas on what my issue could be? It doesn’t feel like a dead cylinder. Anyone with similar problems? Any suggestions are welcome.

Hello i had the same thing happen on my 2011 it turned out to be the lifters were stuck , there seems to be a lifter problem in the 5.3 liter and it starts with insufficient oil pressure, i believe they had a class action law suite for this problem, but judge threw it out, now the dealership is replacing lifters luckily i had 4500 miles left on drive train warranty, just to fix one side is about $4000.00 warranty wont fix both sides, and i hope the other side goes out quickly, so warranty company pays twice. Gm knows about this problem and wont recall.