Engine Misfire Due to Worn Valve Seat on GMC Envoy

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
RepairPal Verified
Average mileage: 111,461 (57,000–253,425)
Engines affected: 4.2L 6 Cylinder, 5.3L V8
6 model years affected: 2002, 2003, 2004, 2005, more2006, 2007
43 people reported this problem
Viewing 1 - 20 of 24 problem details
engine idles to rough told it was a cylinder misfire what does it involve is it expensive
My engine has a blinking light on. mechanic says its the cylinder 1 has no compression that's why the truck is misfiring. I don't understand the truck was running perfectly until a cold day came through and I turned it on. it was making a loud clicking noise.
My check engine light came on. I took my car to a local mechanic and had it checked out, the mechanic plugged his device in my car and it read misfire in cylinder #4. The mechanic looked further into the problem and found out that cylinder #4 read a low 70lbs of compression and cylinder #3 has 120lbs of compression. He explained to us that the low cylinder compression was the reason why our car shakes while idling and runs rough when accelerating. He advised us to buy a new car or get a new engine.
misfire cylinder one, check engine on, "turn engine off" warning sign. no pressure. car white cloudy smoke, irregular idle, loss of power. warranty expired.
Shake when driving slowly or stopped. Put on scanner showed #6 not firing. Changed plugs, coil packs, and injectors. Now it worse. Not fixing it yet.
Cylinder 5 misfire , Pepboys said it needs a valve job , for $3400 and now GMC dealer says the head is leaking and it needs a new head, possibly a cracked head?, I read that this is a common problem and GM has changed this head five times so far, so they are prob trying charge me for a new version head and a vale job , $3500 to $4000, this car is way too new for this kind of problem, I don't tow anything with the Envoy or drive it hard, my wife actually drives the kids to school in it. There should be a recall on this problem, instead of keeping it quiet and letting the customer pay for this, I'm not sure what to do, but I know I won't buy another GMC.
Engine misfire at cyl 6. New plugs, etc., cleaned injectors, replaced intake manifiold gasket. No change. Removed head and had a burned exhaust valve at cyl 6.
i have a 2005 envoy with 80K miles, #3 cylinder has 50 Lbs of compression, guess im pulling the cylinder head....
Misfire cylinder 6, dealer (Chevrolet) charged me over $1000 on repairs before diagnosing problem, Now wanting $2612 to repair bad valve.
I have a check engine light. I took it in a found out that it is my valve. Cant fix it right now. Driving minimal.
Multiple misfires
Was told that it needs a cylinder head . Misfire on #3 has been coming up. Had checked out many times . They thought it was Fuel injectors. at first . Then diagnosed with losing compression on 2 cylinders.
engine missing. problem was # 6 cylinder not firing. turned out to be valve and valve seats on head. Had to replace cylinder head.
i have the check engine all the time even if fifed it , it comes back
cylinder 5 misfire, stalls at lights , I replaced coil packs and all plugs , rough idle still
idle rough, check engine light. no. 3 cyl 70 lbs compression. pulled head burnt valve
Cylinder 5 has only 115 lbs and I have the rough idle
I haven't got the problem fixed yet but every time I crack my car it shakes uncontrollably until it warms up after it warms up when I'm in drive and I'm sitting I don't want a red light it shakes uncontrollably it does not shake when in reverse or neutral
#3,4 & 6 low compression # 4 the lowest 90lbs
The engine began developing a vibration at idle speed, especially while in gear. The Check Engine light is on and the only code that shows is a misfire in cylinder 5. Further diagnosis shows that cylinder's compression is 65 psi. I've had estimates of $2,000- $2,500 to fix the problem. The mechanics see pretty sure the low compression is a valve issue. I love the vehicle, but am not sure I want to risk the repair.