The contact owns a 2006 Hummer H3. The contact stated that while driving 45 mph the check engine light started to illuminate. The vehicle was taken to a mechanic who performed a diagnostic test and stated that the engine misfired and had an excessive leak in it. The emission coil was repaired but the problem continued to occur. The manufacturer was contacted and offered no assistance. The failure mileage was 45,014.

- St Petersburgh, FL, USA

I purchased my 2006 Hummer H3 in February 2006. After driving it for approximately 5K miles, the check engine light came on and the vehicle felt like it was losing power. I immediately took it to the Hummer/GM dealer. I was told that the engine cylinder heads needed to be replaced and that there was a problem in the manufacturing process. I was in shock that I had that problem with a new vehicle and I requested that I get a new replacement vehicle because I did not want the "lemon" they sold me with a defective engine. I was assured I had nothing to worry about and that the vehicle would be repaired (under warranty of course) and I would not have the problem again. In November 2010, months after my warranty had expired, my vehicle had the same problem. In fact, it is at the dealer now and I still do not know how much it will cost me to repair it. The only reason it may be repaired at no cost to me is because I paid $2650 for an extended warranty from an outside company (which expires soon). However, my extended warranty company still needs to determine if it will cover the repairs. I did my research and found that many (too many) 2006 H3S have had the same problem with the engine and it is a manufacturing problem that GM is very aware of. However, despite numerous complaints, GM refuses to take care of the problem or issue any bulletin. This is a huge safety issue. If the engine misfires and my vehicle breaks down, it can easily cause an accident and/or rollover, and very well cost me my life and the lives of others. GM needs to recall these vehicles and issue a safety bulletin, and replace all affected vehicles.

- Anaheim, CA, USA

Called by customer complaint of rough idle and misfire. Vehicle is a 2006 Hummer H3 with the L52 I-5 cylinder engine. Mileage is 77675 diagnosis revealed cylinder #5 was bad. Further testing revealed water in the oil. Final diagnosis blown head gasket. This is a recurring problem with this engine and vehicle. Dealer refused to repair though it is the same engine GM issued a technical bulletin calling for changing heads on the Colorado.

- North Charleston, SC, USA

1. during normal driving and idleing I started seeing / hearing the engine misfire and illumination of the service engine soon (ses) I would experience abrupt loss of power or surging or idle roughness. After research and dealer diagnosis we found the early Hummer H3 has the same atlas L52 I-5 engine as the 04-05 Chevrolet Colorado. The 04-05 cheverolet Colorado atlas L52 I-5 engine was given a special coverage for soft engine intake valve seats, extended the warranty to 7 years and 100,000 miles under tsb 07123 NHTSA # 10022722. To fix the problem the head is replaced with one with harder valve seats. The 2006 Hummer H3 should also be covered by this bulletin. GM has refused to cover my H3 with this problem even though it has the same engine simply because NHTSA # 10022722 does not specifically say Hummer H3. My GM case # 71-805764673.

- Wichita Falls, TX, USA

The contact owns a 2006 Hummer H3. While idling at a stop light, the accelerator pedal automatically extended to the floor and the vehicle sped forward. The contact had to depress the brake pedal with both feet to prevent crashing into the preceding vehicle. The vehicle then went into limp mode and would not exceed 20 mph. The vehicle was towed to the dealer and they replaced the throttle body assembly. The dealer stated that this was a common failure with these vehicles caused by a manufacturer defect. General Motors acknowledged the failure and stated that they were replacing the unit with a different part that they believed would eliminate the failure. The replacement would be at the contact's expense. The manufacturer stated that they have not considered issuing a recall because they are repairing the defect as it occurs. The failure and current mileages were 20,800.

- Hopkins, MN, USA

: the contact stated while idling at an intersection, the check engine light illuminated and on star was called. There was an advisory to drive the vehicle slowly to the nearest dealer. Diagnostic testing was performed and they determined a cylinder was leaking and the head and valve needed to be replaced. 12,000 miles after the first repair, the identical scenario recurred. When the vehicle was taken to the dealer, they determined the diagnostic code was the same as the previous visit. Another cylinder was leaking and it needed a head and valve job again. The service manager expressed the reason for the recurrence was due to the design of the head which was installed when the vehicle was manufactured and during the replacement. The manufacturer was contacted, and determined that there was now a new part for replacement. The contact was concerned that the original part and the new part had the same part number.

- Candia, NH, USA