Troubleshooting misfire

[DBlokker]

Hi,

I've got a 2.0L 16V VW engine (9A) with 42mm ITB's on it. The motor is pretty much bone stock, no fancy big cams or headwork, still 10.5:1 compression ratio. I've got the motor running currently with msns-extra version .021-u3 using a Edis-4 module and coil and a trigger wheel and vr sensor. I've got a LC-1 wideband hooked up.

I had no trouble getting it to fire and run and idle and I've takin it on some short drives to start datalogging. The problem is that it has an intermitant misfire. Sometimes it will misfire idling for about 20 seconds and then stop and run fine or some times it will misfire off and on.

Now I'm thinking that this has to be something outside of the megasquirt unit. It's a computer after all and it shouldn't screw up and forget to tell an injector to fire. Right? Is there anyway to bench test an injector to see if it is operating correctly? What about the edis trigger wheel, what if it runs out about 1mm when it is rotating? WOuld this be enough to cause it to not send a signal? My VR sensor wires are not shielded yet, could this be causing this?

Does anybody else have any ideas about troubleshooting this?

Oh, and I've checked my logs and there is no tach spikes or other oddities when it is misfiring, other then AFR going leaner.

Thanks in advance,
-Dan

[newtyres]

Without looking into the requirements of your setup I noticed an intermittent missfire on the bench on my setup if I didn't use the pullup resistor to 5V on the spark output from the MS chip.

Ian.