Check the air filter, and change it if it's dirty. Usually if there is a sensor bad, or something like that, the service engine soon light will come on. There is a code stored inside of your computer somewhere causing the light to come on. Take the truck to autozone or someplace like that, and they will scan your engine for free. There will be a code, write it down and let me know what it is. If Autozones' scan tool cannot find a code then you need to take the truck to a mechanic that has an advanced scan tool. Usually, this means a trip to the dealer.
GM has had lots of problems with the fuel injector design on these engines. I have heard of a recall on these injectors but I am not positive. You should ask your local dealer about that. I do know that the upgraded injector system works much better than the O.E.M. Injectors. This may be the problem.
Also, I am assuming that your engine is a 5.7L or a 5.3L V8 cylinder. The lower intake manifold gaskets commonly fail on these engines.--Is your engine coolant low?--If it is this may be your problem.
The gasket fails and leaks; sometimes outside the engine, and sometimes inside the engine. The gasket may be leaking coolant into one of your cylinders. This will cause the engine to run rough.
So, start with finding out what the code is for the check engine light---check back here and let me know what the code is for the light--we will start there
Thursday, January 10th, 2008 AT 9:42 PM