2009 Buick Other

Engine Performance problem
2009 Other Buick Models 6 cyl Front Wheel Drive Automatic 20,000 miles

My Enclave started missing with my cruise on about 9 months ago while returning from a long trip. When I would take the cruise off it would stop. Then it began doing it without the cruise on. Seemed to do more so when going up a slight upward slant on the highway. Took it in to the dealership and was told a spark plug needed to be replaced. It worked fine for about 4 months. Then started to do it again. Took it in again and the spark plug was replaced again. Drove fine for 4 days. Then right back to missing again. They say they can not find anything else wrong with it. Any ideas?
January 10, 2010.

As this is still under warranty it is not really ours to give advice. But I would change the fuel filter and put a good fuel injector cleaner and run that through and see what happens. If you do a lot of shorthops that is very hard on a car engine and it tends to build up carbon/oil deposits. The fuel may be partially blocked

Jan 31, 2010.