2014 6.2L Misfire

Ekordas · July 21, 2015

Anyone have a service engine light and misfire on their 6.2L around 5000 rpm? Been in the dealer twice and I just picked it up and had it scanned again and showed 1300 misfires on cylinder 8, 28 on cylinder 7, and between 2 and 4 misfires on a couple other cylinders. I know its not bad gas and they already tried replacing all 8 plugs and wires. I was also getting an error code for the transmission control module and brake control module.

Jordan18 · July 21, 2015

How many miles on your truck?

2B-4G10 · July 21, 2015

try and check for the Airflow sensor, the exhaust catalyst sensors (especially bank 1 -pre catalyst-)...good luck

ghgmi · July 21, 2015

try and check for the Airflow sensor, the exhaust catalyst sensors (especially bank 1 -pre catalyst-)...good luck

If it were something like that, why would the misfires be skewed so much toward cylinder 8?

2B-4G10 · July 21, 2015

If it were something like that, why would the misfires be skewed so much toward cylinder 8?

I'm not sure or certain but it seems to be electrically caused. I've had similar problems that were related to MAF sensor, catalyzes sensor, camshaft sensor..etc

As much as I love American cars but let's be honest here...the electricity sucks big time, the harnessing and wiring are just so unreliable and tend to break all the time.

ghgmi · July 21, 2015

I'm not sure or certain but it seems to be electrically caused. I've had similar problems that were related to MAF sensor, catalyzes sensor, camshaft sensor..etc

As much as I love American cars but let's be honest here...the electricity sucks big time, the harnessing and wiring are just so unreliable and tend to break all the time.

Thanks. The only sensors I can ever recall having trouble with were ABS sensors and O2 sensors. I don't think I've ever had a wiring problem in a vehicle. (Edit: I've had failed relays and electric motors.)

redwngr · July 21, 2015

No misfires or CEL's.

(Also don't think its' been to 5000)

Is it a 14 or 15?

I'm wondering if it's losing a signal somewhere and the problem is vibration induced at high rpm.

Interested in what you find.

Ekordas · July 21, 2015

It's a 2014 with 26,000 miles. The engine light will flash at much lower rpm while towing a load. It seems to be an engine load induced misfire. On my way to the original dealer I purchased the truck from to see what they say.

BuyAmericanIron · July 22, 2015

I would request some diagnostic work. Everyone always wants to go to the electronics or a sensor or check the GM log file for TSB's or what other mechanics have found. Technician may need to do some digging. Let's get back to basics. The engine needs basic things. 1) Air 2) Fuel 3) Spark Considering the problem has seemed to move around to different cylinders, I would check fuel pressure. It may be as simple as a fuel pressure regulator or a fuel pump. Under max load and/or RPM's this is where a weak link will show up. Are the coil packs receiving proper voltage? Are there leaks in the air intake system? Clamps all tight and in place? Just some questions I would ask or want them to verify? There have been some valve spring problems in Corvettes, which I have read have the same parts as our trucks. A weak valve spring will show up at high RPM and is harder to diagnose. Experienced this on an engine I built once and it took a while to diagnose the root cause. Once new springs were installed, engine ran smoothly all the way to redline with no further issues. Engine had proper fuel pressure and flow and spark voltage was up to spec. Just some thoughts and hope they help out.

Ekordas · July 27, 2015

Cylinder 8 coil pack replacement did not solve the issue. Not sure what the dealer will try next.

fondupot · July 29, 2015

I had an issue with my truck misfiring back when i first got it. All of the plug and wire connectors were dry, meaning there was no dielectric grease in them. Also, had a bad spark plug. After greasing up all the connectors and replacing a spark plug, truck has run fine ever since. Knock on wood.

Ekordas · July 30, 2015

So first attempt was a cylinder 8 plug and wire, second attempt was all 8 plugs and wires, third attempt was cylinder 8 coil pack, fourth attempt was cylinder 7 coil pack. Truck still misfires. Unbelievably frustrating.

BuyAmericanIron · August 1, 2015

So basically what you are saying is that they are just throwing parts at your truck and hope to get lucky and find the right one? I would look for a dealer that has a technician that will actually do some diagnostic work and find the root cause of the problem. At that point, it can be repaired with one visit instead of playing the guessing game at your expense. I would be asking for a compression test and a leak down test. If both of those come back good, your dealer needs to dig a little deeper and check valve spring pressure. You did not mention how many miles are on your truck. Do you run an oil catch can? If not and you have over 30K miles, you may have excessive valve coking interrupting airflow on cylinders 7 & 8 which could lead to misfire at high RPM. It may be time for them to pull the upper intake manifold and look at your valves. Just some additional thoughts.