I have a 1999 Olds Alero 2.4 that is driving me nuts (a short trip). It is misfiring on 2 cylinders but does not generate any error codes. I have replaced the plugs, boots, coil housing and coils, and a different ICM has been tried. The fuel filter has been replaced. Injectors have been swapped around, but it still misfires on the same two cylinders.
Both the repair shop and I am at a loss for what to try next. Any suggestions?
Are the two misfiring cylinders adjacent to one another? If so, have a leak down test performed on those cylinders. A leaking head gasket can cause a misfire in two adjacent cylinders.
Tester
According to my mechanic (who is outstanding, by the way) it is missing on cylinders 1 and 4, opposite ends of the block, which is what makes this thing so baffling.
I would still do a leak down test on all the cylinders. If cylinders 1 and 4 have low compression it’ll cause a misfire in those cylinders.
Besides, a leak down test is one of the first things that are performed to make sure there’s nothing wrong with the engine mechanically to cause a misfire in any of the cylinders.
Tester