01 Regal p0300

[84hurst]

Had a customer bring in an 01 Regal (3.8 NA) with a complaint of a no start. Well it turned out the starter was bad as well as the flywheel (a couple chipped teeth) so we pulled the motor to replace the flywheel. Got the car done and running on Saturday with an obvious misfire. P0300 code came up on the scanner (multiple cylinder misfire). Upon trying to diagnosing the issue I found that the misfire is only on cylinders 1 and 4. I found this out by unplugging the injectors. Tested spark and found that there is weak spark at the coil pack (1 and 4 are both on the same coil).I thought, well thats easy, I'll just replace the coil. No change. I tried two different coils be be sure. I replaced the ICM and all 3 coils. No change. Tested continuity from the harness to the ICM. All good. I know that the ICM is grounded through one of the bellhousing bolts (which I did have apart when I had the motor out) but it is difinately connected and am getting a good solid ground. I have the feeling this issue was there before we touched the car but the customer is certain it was not. I am pretty familiar with the 3.8 motors but I have not seen this issue before. Any help would be appreciated! Working for free for this long sucks!

[GTP Dad]

Did you remove the plugs and see what they look like. I suspect that they may be fouled due to the weak spark. Also you don't say how many miles are on the car but it is high mileage you may want to replace the spark plug wires at the same time. The biggest cause of multiple misfires are either bad plugs or bad plug wires.

[84hurst]

Thanks for your reply. It turned out the number 1 plug wire was bad. We replaced the one for now and are going to have the customer come back soon so we can do a full tune up on it.