Engine Misfire Due to Worn Valve Seat on GMC Canyon

Problem Description and Possible Solution

The engine may develop a misfire due to worn valve seats. This fault will cause the Check Engine Light to illuminate. Replacement of the cylinder head may be required to correct this concern.

Problem Data
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Average mileage: 106,040 (28,000–221,000)
Engines affected: 2.8L 4 Cylinder, 3.5L 5 Cylinder, 3.7L 5 Cylinder
4 model years affected: 2004, 2005, 2006, 2007
38 people reported this problem
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Viewing 1 - 20 of 29 comments
Rough idle, Check Engine light (P0300), cylinder leak test shows #2 cylinder leaking (intake valve).
Poor idle, terrible gas mileage, hesistation, gmc mechanics request new cylinder head and valve job.
Determined that the valve seats were bad and the cylinder head needs to be rebuilt at the cost of over $2000.00. It is our understanding that GM knew of this problem and didn't notfiy anyone. Also, we have been told that since we are just over the 100,000 mile limit there is no coverage.
Check engine light on. P0301, P0300.
CHECK ENGINE LIGHT ILLUMINATED, ENGINE MISSFIRE CODE, TRUCK IDLES POORLY, WHILE IN REVERSE IT WILL ACTUALLY DIE AT THE BOTTOM OF DECELERATION AT LOW SPEEDS
My service engine soon light would come on and go off repeatedly. My truck began to idle really rough with low rpm while stopped at an intersection. I went to my local GMC Dealer and they diagnosed it as needing new cylinders and the extended 7 year 100,000 mile warranty covered everything.
The vehicle goes into power loss mode and won't go over 30 mph
Replaced the cylinder head
Truck sputters on idle at intersections. Was just told it will cost $4600 plus tax to repair. 7 year warranty ran out last year, of course. An engine should run more than 55000 miles. Very disappointing.
Multiple cyl. misfiring, gas mileage has depleted drastically. Most problematic gm I've ever owned, sadly disappointed!
I TOOK IT IN BECAUSE MY WATER PUMP WENT OUT FOR THE 2ND TIME ALSO TOLD THEM HAD THE SPARK PLUGS CHANGE AND IT STILL HAD A MISFIRE THEY TOLD ME IT WAS THE NUMBER 5 CYLINDER HEAD WAS LOOSING 80 % COMPRESSION
PAID TO HAVE IT FIXED ALONG WITH MY A/C RESISTOR AND CONNECTOR WHICH WENT OUT ABOUT 50 MILES AFTER WARENTY WAS UP GET IT BACK AND IT STILL HAS A MISFIRE COME TO FIND OUT THERE WAS A RECALL ON THE VALVE SEATS AND CYLINDER HEAD BEFORE 100000 MILES MIND YOU I HAVE HAD MY TRUCK IN THE SHOP MORE THAN ONCE ON IT MISFIRING
MY TRUCK IS RUNNING WORSE NOW THAN WHEN I TOOK IT IN I AM TAKING IT BACK
I believe this is the problem with my 2006 canyon. I have brought the truck in at 33000 miles when check engine light came on, they replaced the emissions canister valve, computer read po 300 and po499. I brought truck to a shop when light came on again and was told to bring to a gmc dealer because test was done and he found cylinders 2 and 5 to have misfired the most. Gm service ran the computer again came up with po 300 and po 449 again. They wanted to replace the same part I replaced under warranty a few years back.Replaced the part and was right back the next morning with check engine light on. hooked to computer again and still reads po300 which is a misfire but they claim the leak down test is within the allowable range and have no idea what is causing the misfires. waiting to hear what they come up with next. I think it may be time for me to call GMC myself and start complaining.
I had this problem, this was one recall on the truck. I took it to the dealership to get it fix in 2007. From what they told me cylinder 2&5 had the misfire. They said the coils were OK, they replaced cylinder head with updated version. The problem came back not to long after they apparently fixed it. Still to this date 2016, and I'm still showing a misfire. I'm wondering is this going to be a continuous problem in this truck and is their anything we can do to have GMC fix this regardless of how many miles is on the truck. They knew this vehicle had this problem and yes the recall was sent out cause I received a notice of the recall but if it was fixed and it still came back then they should fix this so it won't happen again. Need some advise.
My 2005 GMC Canyon is idling very rough and feels like it's going to die at lower rpm, I took it to the dealership and was told the number two cylinder head is firing at very low compression. They quoted me $3500 to repair. The engine only has 58,000 miles on it, shouldn't the vehicle run a little longer than this?
check engine light on. shaking idle
engine light came on. problem was misfire in #1 cylinder. can not find a used engine under 100k. not sure what iam going to do at this point.
Check engine light went on and off and went to dealer who said it was a computer glitch. Vehicle now misfires at low idle. If cost is in the thousands, I will have to find another vehicle.
code 300 not fixed can not afford
check engine light goes on and off. mostly on now cylinder #3 and 5 misfire. I was told about the defected head
valve 2 mis-firing. had to do a valve job.