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GMC Engine & EcoTec3 6.2L Engine Problems- Carbon Build-Up Is Just The Beginning! 

 Gmc 6.2 engine problems

From being durable, cheap and plentiful, the 6.2L GMC Chevrolet engine is a popular choice these days- especially if you are looking to place on in an older 1/2-ton pickup truck or a GMC SUV- as a substitute for a gas V-8 engine. Let’s explore this popular engine as well as what are the most GMC 6.2 engine problems.  While the 6.2 engine is quite a very venerable engine, they were indeed a staple between 1982 and 1993- especially in many GMC/GM light-duty trucks. From full-size vans to GMC Suburban vehicles, the 6.2 was there. In 1994, the 6.2L was replaced by the 6.5L. This engine was then subsequently replaced by the Duramax 6600 back in 2001.

Auto Repairs Are EXPENSIVE


While the 6.2L engines have been out of for about a decade now, you can certainly find a great amount of them on the roads. You can also find several of the engines sitting idle- that could be placed back on highways and byways. This means that if you are in need of an engine, for an older GMC vehicle, you could go with a 6.2 engine. But what about its issues? 


If you’re in the market for a GMC 6.2 engine rebuilding job, then you may want to hold off.  While the 6.2 engine is an ideal engine, the one aspect of rebuilding this engine you want to focus on, is the 6.2 engine’s year.  If the engine you are thinking about rebuilding is before the 1988 model year, you may want to find a newer 6.2 engine for your engine rebuilding job. A 6.2 engine that is newer than the 1988 model year may prove to be better.  In fact, one auto enthusiast stated that should you lift the hood of a 6.2 engine donor vehicle and you cannot locate the serpentine belt system, then close the hood and keep it moving. A 6.2 engine that doesn’t have the serpentine belt system creates a more difficult engine-rebuild job. 


GMC 6.2 Engine Problems- Engine Failure 

One owner of a 2014 Denali reported engine failure with his 6.2 engine. While the owner said that the Denali owned offered plenty of torque for towing a 20 ft car trailer, it used virtually no oil. The owner then reported one day while traveling in the 2014 Denali, the engine began to misfire.  Not only did the “check engine light” came on, it began to miss while traveling up a grade. The owner also reported traveling about 70 MPH and then stopping for a bio break. The 6.2 engine began to miss and the 2014 Denali was barely running. The owner then reported getting back on the road, and setting the cruise control to 73. Once again, his 2014 Denali with the GMC 6.2 engine began to miss. Although the engine never rand hot, it continued to misfire. 

After about an hour of the 6.2 engine beginning to miss, the owner received a message that displayed “Engine Decreasing Power.” The owner stated that the message was indeed what was being experienced.  The starter of the Denali wouldn’t even turn over. The owner called roadside assistance; a tow truck later arrived. Several days later, the 2014 Denali was towed to a GMC dealership for service. The dealership told the 2014 Denali owner that it was possible that the 6.2 engine seized. 


engine was seized. The dealership also pulled the oil pan of the Denali and located two connecting rod caps that were in the pan. The owner never reported of hearing any knocking or any unusual noises. Nevertheless, after experiencing GMC 6.2 engine problems, the dealership ordered a new engine for the 2014 Denali vehicle owner. It was a long block and required a lengthy installation process. 

GMC Yukon 6.2 Engine Problems 

Some of the most common 6.2 engine problems that have been documented with the 2008 GMC Yukon include: 

  1. Engine light coming on due to gas cap issues.
  2. Inability to pass emissions due to gas cap and check engine light 
  3. Gas cap leaks, and more. 

GMC Envoy 6.2 Engine Problems 

Unfortunately, the GMC Envoy has its share of issues with the 6.2 engine. Some of those issues include: 

  1. The engine idling rough, – vehicle owners were reportedly told it was due to a cylinder misfire. 
  2. The vehicle’s engine may develop a misfire because of worn valve seats. 
  3. The engine developing a vibration at idle speed, while in gear. 


What Are The Most Common GMC Chevy EcoTec3 6.2L Engine Problems? 

With GMC’s Gen IV Vortec engine line Chevy began the new EcoTec3 engine line. The EcoTec3 was the successor/ Gen V to the Vortec that was produced back in 2014. The 6.2L EcoTec3 continues to still be the small-block V8 that provides power to the vast majority of Chevy’s performance vehicles. Some of the vehicles include the Camaro SS series vehicles as well as the Corvette C7 vehicles.  In addition to 

being the power plant of various Chevy sports cars, the 6.2L EcoTec3 engine was also manufactured in lots of Chevy’s SUVS and big trucks. With the Vortec still in production, the EcoTec engine line was created to offer a more environmentally friendly and fuel-efficient engine compared to previous engine counterparts and versions. Let’s examine some of the most common issues with the GMC Chevy EcoTec3 6.2 engine problems. 


Carbon Build-Up 

The EcoTec3 engines utilize a direct fuel injection as opposed to port-injection. The port injection fueling allows for the fuel to be delivered to the engine though intake ports. Since the fuel is being spewed into the intake ports, that fuel is pressurized, while acting as a natural cleaner. It also sprays any build up out of the ports. With direct injection vehicles, the gasoline is sprayed right into the engine cylinders. This process allows the fuel to completely bypass the intake ports. Since there is no pressurized fuel traveling through the intake ports, nothing is there to prevent build-up. So, the engine oil burn and the fuel become a byproduct that takes the form of carbon deposits that cake up and build in the intake ports. This is an issue with just about all direct injection engines, causing vehicle owners some performance issues. With the carbon deposits building in the intake ports, the volume of air that the ports can contain, decreases fast. The end result is an engine that doesn’t get sufficient air to perform correctly.  Some symptoms of carbon build-up include: 

  1. Engine misfires 
  2. Poor idling
  3. Acceleration decreasing 
  4. Disproportionate air to fuel ratios, and more.  Additionally, in theory, carbon build-up will begin on day one of vehicle ownership. But a vehicle owner will not begin to notice it- or any performance issues, till the vehicle hits 80,000 miles. 


AFM Issues 

AFM commonly referred to as Active Fuel Management is a fuel efficiency system that basically turns off specific cylinders during specific driving conditions. AFM is also designed to improve fuel economy and offer an environmentally-friendly alternative. AFM also exists to turn the V8 engine into a V4 engine, by completely turning off four cylinders. The concept design behind the AFM system is that the vehicle owner will have better fuel mileage since only a portion of the engine requires fuel. Although good in theory, the AFM system has seen its share of problems. The AFM deactivates specific cylinders from the camshaft though a system of complex lifters. Furthermore, those lifters tend to lack reliability. In fact, they are known to go bad and even collapse. This results in the push rods- which have the job of closing and opening the cylinders- to bend. Should the push rods bend or the lifters collapse, then the cylinder won’t be able to close or open correctly. This can lead to lots of performance problems- especially with the driving of the vehicles. It is almost a guarantee to have AFM issues with these 6.2L engines. Vehicle owners need to ensure that the engines are covered under warranty.


Transmission Vibration and Shuddering 

While the A8 8-speed transmissions are known to have issues on both sports cars and trucks, many drivers will notice vibration during driving. The transmission will feel as if it’s vibrating. The vehicle owner may feel jerking and even shuddering during shifting Additionally, a decrease in smooth driving will take place, with these specific transmission shifts. Typically, the rough shifting is far more noticeable between first and second shift. The issue became such a common occurrence with vehicles outfitted with A8 transmissions that there was a class action lawsuit filed. 


Thanks to that lawsuit, GMC/Chevy posted TSB 18-NA-355 which relates to the issues and the repairs. GMC/Chevy further stated that the problem comes from moisture from the transmission fluid that was utilized from GMC factories. In many instances to remedy the issue, GMC performed a filter replacement as well as a fluid flush. In other cases, a replacement of the torque converter was seen as a viable fix. 


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