Occasionally on my 2008 Avalanche when I accelerate from a cruise mode the engine will backfire. Has anybody else had this issue? if so, what was the cause?

 

Bad valve or a weak valve spring could be it. I would start with a compression check. This will let you know if there are any bad valves.

If the valves are fine then remove the valve covers and look for any worn or broken valve spring which may cause the valve to remain open at higher RPMs.

If these are fine, then you may have a bad crank sensor or even a clogged catalytic converter.

 

If you can't find any of the earlier mentioned causes, you might consider checking out the fuel system. A lean condition can produce a backfire.

 

I am confident tat it is not a mechanical problem. The engine runs very well except when going from cruise to full or nearly full throttle. Then it has multiple backfires. It acts like the ignition does not retard immediately.

 

I think the problem is with the valves, but I'm not sure, it's better to contact customer support. It's just that even the people who sit here and understand cars will not be able to help you for sure because they did not see the whole problem. When I bought my car, I checked its main characteristics here https://accelete.com/ , mainly the amount of horsepower, and acceleration time up to 100 km per hour. You can also read some articles about how the machine should work ideally initially, and then you can try to solve the problem yourself, but still, I advise you to contact the service more often

 

Thanks! It was a fuel system problem. I had replaced the plugs and coils with no effect. I checked fuel pressure. It was in spec. I purchased an inexpensive fuel injector tester on Amazon and extended the 12 volt wires and installed a matching injector connector to it to make it easy to use. Then I removed all eight injectors and thoroughly cleaned them with the tester and carb cleaner. After reinstalling the injectors the random misfire at idle and backfire under hard acceleration were gone.