Do you mean it had a misfire fault code? '96 and newer models will tell you which cylinder is misfiring by the number of the code. The cause can be as simple as bad spark plugs, and bad spark plug wires on engines that still use them. Less common causes are a bad ignition coil and a plugged or shorted injector. GM also has a lot of injector trouble. They can cause misfires that the Engine Computer will detect but you can't really feel.
Once you know which cylinder is setting the code you can switch parts between that and other cylinders, then see which cylinder sets the next misfire code. Instead, if it's been a long time since the spark plugs were replaced, it's just as easy to start with them. Replace the spark plugs, have the fault codes erased, then drive the car to see if a new code sets. Most cars since the mid '90s can get 100,000 miles on a set of spark plugs, but it is not unreasonable to find them causing a problem at the mileage you listed.
Wednesday, May 29th, 2013 AT 11:18 PM