Pontiac Repair: driving issues with 2.4 twin cam, vacuum leak, coil pack

Question
Hi, I have a 2001 grand am, 2.4 twin cam. This is kind of a 2 part question. I have had a cylinder 4 misfire for a long time now. I have replaced the spark plugs, boots, coil housing, ignition control module and fuel filter. I flipped the coil packs to see if the misfire moved but it stayed on 4, is it possible a coil pack is still bad anyway? I did a compression test and the results were all between 160-170. Intake is good, 02 sensor is good. The injectors were tested and ohmed out at 14.5. I went to test the fuel pressure today but can't figure it out. I do not have a port on my fuel rail. I hope this was detailed enough. I've asked many mechanics and no one seems to have answers. So if you could help out I would greatly appreciate it!! Thanks in advance!

Answer
Hi there!


Your all over this. No that engine doesn't have a test port to check fuel pressure. if you swapped coils and the misfire stays put at #4 then you have an issue with that cylinder. It could be a lean misfire due to a vacuum leak or a lean injector. an Ohm test in okay to check it's coil but that is all. as a do it your selfer try taking the fuel rail out and swap the injetor with another one on the rail and see if the mis follows that injetor. did you check to se if the injetor is bing commanded on? use a computer safe tets light and hook it up across the injetor wires with it running the light should be flashing meaning the engine computer is pulsing the injetor.