Hummer
H3
63

Engine Misfire Due to Worn Valve Seat on Hummer H3

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: 85,074 (33,456–199,999)
Engine affected: 3.7L 5 Cylinder
3 model years affected: 2006, 2007, 2008
63 people reported this problem
Comments
Viewing 1 - 20 of 37 comments
Dealer had to replace heads...still under warranty... if it was not it would be big $$$...Gm should do a recall !!!
Same rough idle & check engine light on. Took to dealership under warranty, they said misfire on #5 cylinder & need to replace head. They said it is a common problem with H3. One year later, same problem. Have to take to dealership again. GM NEEDS TO DO A RECALL TO PERMANENTLY FIX IT!!! ITS RIDICULOUS IF THEY ALREADY KNOW ITS A PROBLEM!! I am thinking of getting rid of the vehicle after its fixed because I only have one more year of warranty left & its ashame because the vehicle is very good with no other problems ever with it.
Engine light came on; 2 months after warranty expired, so brought it to dealer and found cylinder 5 pressure was low and need a new head....$2657 later it's as good as new. GM WHERE IS THE RECALL!!!
Rough idle, cylinder head is bad, just out of warranty. Shame on GM.
2006 # MIS FIRE CODE
RUNS GREAT BUT I CANT PASS SMOG MY MECHANIC SAID POSSIBLE LEAKY VALVE ..SO RIGHT NOW I HAVE IT AT THE DEALERSHIP .. WAITING FOR THE CALL TO LET ME KNOW WHAT THE PROBLEM IS..I WILL REPORT BACK
Cylinder 2 misfire. Bought used with no warranty from dealer in 2010. Dreading repair costs to fix it. The idle is so rough now and I put so much money in it thinking I was getting a quality car. Now pissed at GM and will never purchase a car from them again the do not stand by the customers or product and give the recall as necessary.
Check engine light keeps coming on. Have had it on machine twice both times show recent engine misfire. the second time it pin pointed #5 cylinder.Mechanic switched #4 coil and plug with #5 problem still in #5 cylinder. Problem is still in #5
I first noticed an intermittent rough idle when starting the engine while cold. The rpms would hesitate then drop suddenly to below 500 before jumping up to around 1100 and normalizing without any other issues while running. As it started to happen more frequently, I brought it to the dealer and was told that there was no check engine light and they weren't able to recreate the problem. I brought it in twice more and had the throttle body and injectors cleaned before catching a rough start on cell phone video and brought it to the dealer for the fourth time. They advised me that the check engine light should have been lit, but never came on and there was a misfire trouble code. The service report said that there was an "erratic misfire on cylinders 1-4 and a consistent misfire in cylinder 5". They compression tested the #5 cylinder and found the pressure was low due to "leaking exhaust gases". The cylinder head was replaced in accordance with service bulletins and thankfully under warranty.
Same as others , #2 and #5 valve misfire need new head. Why is there not a recall on this?
Engine light illuminated several times over a 2 week period. Initailly, dealer suggested that I check the fuel cap and\or purchase fuel from a "different" station. However, neither of the suggestions solved the problem. Major work (replace head) was required on vehicle. Dealer estimates it will take at least a week to fix it. On a good note: it's under warranty!!
Check engine light came on plus it vibrates alot
rough idle, in shop now, tech says code shows seepage in cylinder, doing a leak test now.

Final report: bad head. Just out of warranty. Cost: $2335 to replace.
bad cylinder head, soft valve seats
Code P0300 Random Misfire. Dealer advised head replacement, cylinder number 5 random misfire. Estimated cost to repair 2600.00 - out of warranty! There should be a RECALL! This is crap I have to pay for this with this low of a mileage!
This is BS....I will not buy another GM product as there was not a recall issued for this rediculus problem that many are reporting. Check engine light came on and cylinder 1 is misfiring at idol with others periodicly mifiring while driving. Mechanic suggestion, new heads at a cost of roughly $5,000 or a new engine at $8,500.
I go above and beyond when it comes to routine scheduled maintenance! I have owned many SUVs that have I have sold in good shape with 200,000+ miles on them and they still run great with the original engine in them.
I don't care if they discontinued the Hummer line if vehicles; I have discontinued my option to buy any GM vehicles until they do the right thing and issue a recall or refund!!
It's a shame, outside this repeated issue, the vehicle is great. Prepair to spend a ton on this issue if you are going to buy a used H3. Who knows what other issues GM is hiding with their other vehicles!
GM - got misfire?
Very low milage on th car. Check engine light came on while on a road trip. Took th car to a mechanic twice. 2 heads have misfired. Can't smog and repair is getting more costly.
P0300 code, soft engine valves! GM needs to do a recall!! For GM to put in soft engine parts that they knew by the report in PIP3935D was a mistake that they recognized and fixed on the much later models. This should be recalled and fixed by GM!!
H3 3500 motor Cylinder 1 misfire, check engine light flashing, replaced plugs and cylinder 1 coil still runs the same will be taking to shop tomorrow
first the radiator cracked and over heated, then the valve head is leaking. 5 grand quote to fix it. Thanks hummer, great product. They all will do this.
Check engine light flashing. Scan found multiple PO300 random cylinder misfire. Mileage 89,729. Performed valve head work that corrected the problem. Roughly $2200.

Luckily I hand an extended warranty.