96 Jetta GL 2.0 runs rough / misfires when cold

jiveabillion · #1 (**permalink**) 11-12-2009, 04:57 PM

I've managed to fix most of the problems with my car, but this one is bugging me. When the engine is cold, it throws P301 & P300 cylinder 1 misfire and random misfire. The codes will go away and stay away if I clear them after it warms up. Anyone know how to fix this?

mcrow · #2 (**permalink**) 11-12-2009, 05:33 PM

Try replacing your engine coolant temp sensor first, its cheap. And how the code stays away after being warmed makes me think this as well. It does help control alot of ignition parts and timing. If that doesnt fix it start testing things in the ignition, start with cheap solutions. The multiple misfire could be distrubuter cap/rotor, coil, oxygen sensor (Would send its own code), camshaft position sensor (Would send own code), spark plugs and wires.

keehn · #3 (**permalink**) 11-12-2009, 08:52 PM

Betcha its either the wires, cap/rotor, or both. Or the infamous cracked ignition coil problem that is all too typical on the MKIII's.

...Or all three of the above. Its likely with the expansion and contraction of the plastic and rubber that the ignition system is grounding out when cold, then sealing itself up when everything expands.

Remove the ignition coil and check the plastic housing for ANY cracks, no matter how small. If you have any, that is very likely your issue and the coil will need to be replaced. Try that first as the wires are more expensive.

Mike (MKIII Emeritus)

jiveabillion · #4 (**permalink**) 11-13-2009, 11:00 AM

I've already changed all but the ignition coil. I could try that.

keehn · #5 (**permalink**) 11-13-2009, 05:29 PM

Quote:

Originally Posted by jiveabillion

I've already changed all but the ignition coil. I could try that.

Let us know what you find out. Remember, it doesn't matter how small the crack is, if the electricity can find a way to ground out, it will. I've seen the ignition coil be the culprit in so many cases that I'm wondering why there isn't a class action lawsuit against VW regarding these failures.

Mike (MKIII Emeritus)