2001 Grand Caravan with the 3.3 Flex engine. ~160K miles.

The van very abruptly started running rough; my wife got it home and I found a P0302 code but nothing else related. (A couple of other codes were present, relating to the evaporative emissions system. They've been present for a while and I've been waiting till it gets warmer to deal with them. I'm not aware of any way this could be related -- am I wrong?)

Plugs were overdue, so I've replaced them. All were worn, but looked good otherwise, including the plug from cylinder 2. I'd expect it to be wet if it were an ignition problem, but it was a nice tan and completely dry. For what it was worth, I checked the new plug before I put it in, and am not getting a spark (holding the plug against the valve cover or exhaust manifold), so it seems like the cylinder is completely dead. For good measure, I have checked the resistance of the plug wires and the coil pack, and those seem just fine.

So my thinking is that the problem is that the PCM isn't causing the injector to pulse and is also failing to order a spark for the cylinder. Sound like a reasonable conclusion?

If so, is it automatically a problem with the PCM, or could it be a problem with either the crankshaft or camshaft position sensors? I only know what they do in a general sense. I don't know if a problem with one of those sensors could cause a shutdown of a specific cylinder; I'm guessing they'd prevent starting all together.

Let me know if more info would be helpful, and I appreciate any thoughts you might have.

 

Welcome to DF
Do a compression test on the cylinder that you think is dead. Next if the compression is good, open up the wire harness on the rear cylinder next to the p/s reservoir. There has been a problem with wire harness.

 

Thanks. I'll check the compression tomorrow, and will then check the wiring. Are you referring to the bundle that connects to the coil pack?

Just because I'm trying to put all the pieces together in my head, would the PCM turn off fuel and/or spark if it detected multiple misfires?

 

The one that leads to all of the wires on the injector harness. Unplug the big rectangle connector and pull it toward you a little.

 

Im having the same problem you are....plugs replaced, wires newer...but still dead, like it's not getting any fuel.

 

I did a little more checking on things and found out that my understanding of how the coils fired the cylinders was incorrect. I was getting spark on the companion cylinder of #2 (#5) which led me to believe that the coil was OK and the problem was with the PCM or a sensor. Turns out that the PCM just sends one spark command that fires both cylinders, which means that the coil was bad.

I replaced the coil pack and everything's fine. I don't understand why the plug wasn't fouled, but that's a mystery for another day.

Thanks for your responses.