P0351
P0351 My Z28 started missing and threw this code. Ignition coil A is bad. Simple enough. I replaced the coil with a Denso piece, new wire, and an AC Delco iridium plug gapped at .040, all from
Autozone. As soon as I pulled out of the driveway, it did it again. Worse, actually. So I got it diagnosed at a friends shop. Bad coil. Ohm range was all over the place, he said. Wiring didn't have any issues. I exchanged the coil for another. All seemed well. It ran perfect at all rpms until a few days later. Then it started missing again and throwing the same code. Surely I wouldn't get two bad coils out of the box in a row. The problem is hard to duplicate, as there is no rhyme or reason for the time, place, temperature, condition, etc etc etc it chooses to do it. The only two things that are consistent are the RPM range during which it happens (anywhere from 1500-2500, mainly in first and second gear it seems?) and that if I power through it and hit the gas I can hear detonation at higher RPM (I know, I know... Don't do that.) It does it to me all the time, until I need to show someone what it's doing. Which is why this is so infuriating. I'm going to swap coil A and B tonight to see if the problem moves. Just wanting to see if you guys have any pointers. I know literally nothing about wiring so please be patient and simple with me lol thanks guys
Edit: I'm an idiot... Probably oughta try a coil from my Trans Am that I park next to every single night first.
Autozone. As soon as I pulled out of the driveway, it did it again. Worse, actually. So I got it diagnosed at a friends shop. Bad coil. Ohm range was all over the place, he said. Wiring didn't have any issues. I exchanged the coil for another. All seemed well. It ran perfect at all rpms until a few days later. Then it started missing again and throwing the same code. Surely I wouldn't get two bad coils out of the box in a row. The problem is hard to duplicate, as there is no rhyme or reason for the time, place, temperature, condition, etc etc etc it chooses to do it. The only two things that are consistent are the RPM range during which it happens (anywhere from 1500-2500, mainly in first and second gear it seems?) and that if I power through it and hit the gas I can hear detonation at higher RPM (I know, I know... Don't do that.) It does it to me all the time, until I need to show someone what it's doing. Which is why this is so infuriating. I'm going to swap coil A and B tonight to see if the problem moves. Just wanting to see if you guys have any pointers. I know literally nothing about wiring so please be patient and simple with me lol thanks guys
Edit: I'm an idiot... Probably oughta try a coil from my Trans Am that I park next to every single night first.
Last edited by sawblade99Z; Aug 13, 2014 at 11:29 PM.
Update: switched coil in question with a known working coil from my Trans Am. Initial drive seemed smoother. No detonation in upper rpms. Then I accelerated normally from a dead stop and the misfire came to party again. I'm at a loss here. It's throwing a code for a coil... But it's not the coil... Nor the wire and new plug... Wiring is supposedly all good... What else could it be? If all else fails, the LT install will be coming along a lot sooner than expected, as well as truck coils and all new plugs and wires.
my guess at the moment without looking into my service manual, is that circuit driver for that coil within the PCM is bad. if you keep throwing coils at that specific location and keep having the same problem, the common denominator is the PCM switching circuit for that coil that grounds it causing it to fire. +12v power wired to that coil is common to all the other coils.
other than that you may have a bad connector at the coil or elsewhere, or possibly the wire chaffed somewhere that goes to just that coil on either the + or - side, or possibly a bad pin or connection in the harness connector at the pcm. remove the pcm connectors and look for any signs of burnt or corroded pins, and carefully inspect all wiring specific to that coil.
other than that you may have a bad connector at the coil or elsewhere, or possibly the wire chaffed somewhere that goes to just that coil on either the + or - side, or possibly a bad pin or connection in the harness connector at the pcm. remove the pcm connectors and look for any signs of burnt or corroded pins, and carefully inspect all wiring specific to that coil.
I called the guy who looked at the car again this morning. Although he told me it was a coil last time, the first thing he said when I told him what was going on was, "it was a control code" or something like that. Seemed to indicate that it was, in fact, an issue pre-coil somewhere in the wiring or PCM. He's going to look it over tomorrow. Thanks for the reply. I'll dig around tonight and see if I can figure anything out, before I take it to the shop.
