Hi Scotty.
I have a 2015 Jeep Grand Cherokee with 111K Miles. Symptoms: shakes sporadically at idle mainly while in gear, bucks sometimes during acceleration. There is a code PO305 that recently popped up which indicates a miss fire in cylinder 5 due to bad coil pack, spark plug or clogged fuel injector. Is there a reliable way to check the coil pack to see if it has failed or has an intermittent problem? This is listed a a probable cause but I have heard that coil packs don't typically fail.
Thanks in advance for any reply or advise.
Cheers, Scott
Take the coil pack and switch it with another, If the misfire moves, you know it was the coil pack.
It is rather rare, but my 98 4runner had it happen. It never threw a code, but I noticed that when going up a hill nearing the slowest speed in overdrive, it would often misfire. Upon inspecting the coil packs, I noticed one had some green on the copper electrode. Sure enough, one new coil pack later and the misfire was gone.
Yes, pull the spark plug and check for spark. See FAQ for details.
