Cylinder 8 Misfire Detected

I’m contacting you regarding my 2019 GMC Sierra 1500 with the 5.3L V8 engine. The vehicle is currently experiencing a cylinder 8 misfire (code P0308), accompanied by engine backfiring, ticking noise, and exhaust fumes inside the cabin. Additionally, the ESC (Electronic Stability Control) warning light is on, and performance is noticeably affected. To date, I have: •Replaced all spark plugs and fuel injectors •Verified proper ignition coil function •Had an oil change on September 23, 2024, during which I reported early concerns about engine performance (shortly after the powertrain warranty expired) •Had a transmission flush on March 17, 2025, in an attempt to resolve continued drivability…

I brought in vehicle for check engine light is on for p0300 / p0308 had misfire tech removed engine valve cover and determine no movement in valve train components tech determine valve train failure lifters possible camshaft we would need to remove the cylinder head and replace valve train lifters.

Vehicle started showing a po308 code. Called sewell gmc In midland where I purchased the vehical they were 2 months out on diagnostic services. So I took it to another shop. They ran a camera into the problem cylinder and for scaring on the walls. They said it was due to the afm system and the engine was unrepairable. So now I am out 17,000 dollars and stranded over 700 miles from my home due to a manufactured defect.

Vehicle lost power, debris in cylinder from internal damage, crank case leaking air, oil leaking into cylinder, P0300, P0308, and P050D

…On March 26th, 2026 while driving on the parkway at about 60 mph, my vehicle experienced loss of power (slow deceleration, shaking/hesitation) and I immediately took it to the repair shop where it was diagnosed as a P0308 code (misfire on cylinder 8) which caused a repair of the #8 spark plug, ignition coil and wire resulting in a $380. repair. Two days later, I experienced the same issue and then took it to an engine diagnostic specialty shop where I have been told that this issue will run about $4,000 due to valve and comprehension issues on an engine that has 60, 680 miles. I have seen numerous L87 engine complaints on Chevy Forums with no assurances that repairs or engine replacement…

AFTER PURCHASE, I GOT A CONTINUOUS P0308, CYLINDER 8 MISFIRE. PROBLEM IS THAT CYLINDER 4 HAS LOW/NO COMPRESSION, DRAGGING DOWN CYLINDER 8 AS WELL.

ENGINE TICKS AND LAGS/HESITATE UNDER THROTTLE RECEIVE ERROR CODE P0308, DEALERSHIP RECOMMENDED A TUNE UP BUT DID NOT RESOLVE PROBLEM. STILL HESITATES UNDER THROTTLE. DID EXTENSIVE RESEARCH ON-LINE AND THIS IS A COMMON PROBLEM WITH THE ENGINE AND COSTLY TO CONSUMERS AND DANGEROUS. IN MY CASE, I WAS ENTERING A HIGHWAY WITH MY 2 KIDS. I WAS ON THE FRONTAGE ROAD GOING ABOUT 40 MPH AS I ENTERED THE ON RAMP OF THE FREEWAY TO GET TO THE SPEED LIMIT OF 60 MPH. WHEN I ACCELERATED THE ENGINE STARTED TO HESITATE AND ALMOST STALLED CAUSING THE VEHICLES ON THE FREEWAY TO SLAM ON HIS/HER BREAKS AND SWERVE TO GO AROUND ME. FORTUNATELY, THE CARS BEHIND ME DID NOT RAN INTO ME OR ANYONE ELSE CAUSING A MAJOR…

I was experiencing rough gear shifting jumps and low power/acceleration but it was spotty and not continuous. While I was traveling on cruise control, my truck started misfiring. Once I got home the whole truck was shaking in place. I popped the hood and noticed the engine itself was shaking on the motor mounts. On the way to the mechanic, several lights (including check engine light) came on (the codes thrown were P0300-P0308). The mechanic attempted to clean the fuel injectors (that were replaced 30k miles go due to failure as well), but that did not solve the misfire. I was told the cylinder was dead, and upon inspection of the oil filter there were metal shavings throughout it and the…

While driving my 2018 Silverado, the 5.4L, 327c.i. engine began idling very rough, shaking and periodically stalling. The check engine light began blinking and it threw codes PO308 & PO301. After compression test & new plugs/wires, it was found that the injectors had open circuits on injector #'s 1 & 8. The only way to replace the injector is through the bank. In this case both banks 1 & 2 were affected. Cylinder #1 is through bank #1 & cylinder #8 is through bank # 2. After removing the intake manifolds and injectors, it was found that the injectors were not providing fuel to the engine causing a misfire on 2 random cylinders #1 & #8. Called the dealer to order parts and discovered they…

Knocking noise from engine-no check engine light initially. Next time it was started knocking was still present and the check engine light was on. Contacted Champion Chevrolet in LaGrange KY. Dealership diagnosed problem (Code P0308 - Cylinder 8 misfire). Compression test on Cylinder 8 failed. Removed valve cover and confirmed loud tick in the rocker shaft and worn camshaft lobes. Was told I would need a new engine and that repairing the existing engine was not cost effective. So, $22,722.14 later, i have a new engine in my 2020 GMC Yukon and have the original engine (core charge) in my shop in case it is needed for evaluation to help determine if the GM recall should be expanded to 2020…