2001 Suburban - Cold "Random Miss" At Idle - Coil?

['00SonomaZQ8]

I've noticed since the weather cooled down last month that the cold idle on my Suburban has been choppy, but on a trip up to Colorado earlier this month I remote started it and found it had thrown a code while warming up. I took it down to the parts store and they pulled the code, a "random miss". I didn't know it could be random, I thought it would give me a cylinder, but oh well, it was running fine after warming up, so I didn't worry about it. The CEL went off after a few cycles and all was well until the morning I left to come home, which was a repeat of a few days prior, code thrown during warm-up. I drove it home with the CEL on the whole way and stopped by a parts store near home just to make sure it was still a misfire, and it was. After a few more cycles the CEL went off again.

 

Well, the other morning it was cold enough to misfire during a remote-started warm-up and now my CEL is on again. I'm pretty sure it's a coil going bad, but how do I determine the culprit?

[Carder09]

Maybe knock sensor.

[servantsalesmen]

It could be a gazillion things my friend. I'd take it to a shop that has a tech 2 scanner. It will give you way more information than the scanners auto parts stores use. From there you will be able to make a more education assessment and come up with the correct fix the first time. Good luck!

[gapost]

I would think a back knock sensor would show the code specifically for that. I had an erratic miss on my 03 Sierra and after a lot of time and some work on various things, I replaced the plugs and wires and it runs perfect. But, it didn't pop up any code. It could be a bad coil, but those are pretty rare. If you haven't replaced plugs and wires I would try that, at least try plugs first. The tech2 might be able to identify the bad coil.

['00SonomaZQ8]

I did a full tune-up in August with GM parts. The fact that it only does it cold makes me think it's a coil just starting to go. I guess I'll just have to pay the $80 for a real diagnosis at the dealer and see what they think it is.

[efritz]

spray some ether around the intake cathedrals when it's idling, if the idle speed changes, the intake manifold gaskets are leaking, a very common problem and easy fix as they are dry. Try that first, as the problem is usually cold sensitive. This condition will set a P0300 code.