I have a '91 chevy cavalair whose #2 & #3 coils are not firing. We’ve replaced the spark plugs and the coil pack but to no avail. Last thought may be replace the on board computer, your thoughts? Can’t quite go around driving on two cylinders so by chance your expertise will solve this mystery
Move the plug wires from one coil to another, any change? Are the wires damaged at all? Plug wire boots pulled or wires yanked on?
You need to do some electrical troubleshooting using a digital multimeter. Make sure that the coils have 12 volts on the small wire. The other small wire is grounded each time a spark is needed. On some cars, it’s grounded by an ignition module. On other cars, it’s grounded by the engine computer. The wiring diagram will reveal which is the case.
You did not state which engine you have (4 or 6 cylinder) but making a wild guess here, I will assume you have the 4 cylinder.
When you have adjacent cylinders misfiring (2 and 3 in this case) this can point to a failed head gasket.
Any time the spark plugs come out for an engine performance problem a compression test should always be run. This will tell you right off the bat if you’ve got a mechanical problem and save repeated trips to the parts store to purchase parts that will accomplish nothing.
Run a compression test and post the numbers. Even on a high mileage engine you should get 150 on up on all cylinders and the readings should be very close to each other. If this is a 4 cylinder and both 2 and 3 are down on the numbers then odds are the head gasket has given up.
There is plenty to do before just throwing parts at it blindly. The wiring harness needs to be evaluated with a multimeter, the ignition module can be tested, and signals from the ECM can be checked and tested as well. Are you positive your not getting spark, or can there be a mechanical problem causing a mis-fire?
Thanks for each response, we’re going to plug away checking the ignition module, then the other options mentioned. I’ll be sure to post what resolved this matter. Thanks again
Well we replaced the inigition module and she’s back to running the roads on 4 cylinders. Thanks again for your assistance
That’s great…if it’s a 4 cylinder engine! Otherwise, you have only two more cylinders to fix (if it’s a 6 cylinder). Let me guess, you just changed a part, the ignition module, and you were lucky enough that that was the problem, right?
Good evening I have a 89 Camry having a misfire in #1 and 2 cylinder it overheat 2 times from December to February because a fan once and radiator cap now I change coil same problem