Dealer called to tell me the car was finished, but that the number 4 cylinder has a misfire when they checked codes after taking it for a 10 minute test drive. He said the code was P0300.


They said the computer has this code stored from before I brought it in for the new head gasket and intake manifold gasket. So they suggest($400+)new wires, plugs, PCV, and to purge the injectors.


I don't disagree about changing the wires, plugs and PVC as all are about 4 years and 60,000km old, but surely I can do this myself. I've done this on other GM's, but the service guy stated that this is more complicated on the dual overhead cam..........why would that be?


As for purging the injectors, am I stuck with having the dealer do this? Should I try a product that I can add to the gas tank?


I questioned if it is possible to move the coil pack at #4 to another location on the ignition module to see if the misfire moves......there was a long pause....then he again suggestednew wires, plugs, injector purge, and PVC. I'm not sure if he knows what I am talking about or if I said something stupid. Please be kind, but did I say somethingstupid?


Could the failed intake manifold gasket cause a vaccuum leak, and hence the code. It did fail at the #4 cylinder location? When they changed the head gasket and intake manifild gasket, would they have not disconnected the battery, and if so would the past codes not be lost?


Other than the leak the car ran well when I took it in, so is there anything they may have done to cause the problem?


Advice?