If it feels like a single cylinder misfire, unplug one injector at a time to see if you can identify one cylinder that isn't working. That's a manual version of the old cylinder balance test.
If you have a scanner that displays live data, you can look at the oxygen sensors and fuel trims to possibly point to which bank has a problem. There should also be a misfire counter. It takes a certain number of misfires before the computer will set a code and turn on the Check Engine light. Before a code is set, the computer will watch a problem that it suspects might continue to act up. Those are called "pending codes", but then you're getting into an area I'm not real familiar with.
You can also measure the resistance of the injectors. Here again, GM seems to have more trouble than anyone else. Look for one that is considerably lower than the other five. That difference could be only a half ohm.
Tuesday, November 30th, 2010 AT 6:20 PM