Leaking IACV Causing Misfire?

[mdmellott]

I had a suspect IACV going bad but had no DTC. I ordered a new one but had no time to wait for delivery and install it because I had to drive for work from the San Francisco Bay Area to Sparks, NV. Not long into the drive I started getting a misfire on #3, which I confirmed later when I got back home. At first, my check engine light would only flash momentarily and then turn off and this was only happening under load at a low rpm or while accelerating from a low rpm. All the way up into the Sierras this happened and then the CEL finally stayed on full time. My new IACV had been delivered and I installed it immediately. My idle issues that I knew about were fixed completely. The old IACV had a gasket leak which wrecked the stepper motor. Could this leak, sucking antifreeze into the intake, cause a misfire? The abrupt misfires I had experienced up and down the mountain also seem to have stopped happening since I replaced the IACV. I would not normally associate a misfire with a bad IACV but it does seem to be related in this case. I made it back from the Sierras but I'm not convinced that I'm out of the woods yet. Is it possible I also have a poor grounding issue with that one coil? I'm not really sure where to probe it to find out.

[VStar650CL]

Sure, having "water injection" primarily to one cylinder could definitely cause a miss. It'll cool the charge and combustion chamber relative to the others, causing a lean condition. To check the coil ground, back-probe the coil ground wire and measure to the block with the engine running (we know your main ground is good from the exhaust straps).

[mdmellott]

Thank you. I was guessing that might be the answer but doing this while the engine is running was making me a bit nervous because I wasn't sure. I just need to be sure I back-probe the right wire or else I'll be smoking that coil and/or my multimeter. Maybe not.

[VStar650CL]

No, the meter is high impedance when set on voltage, there's no risk of smoking anything. It's only a mis-connected ammeter or ohmmeter that can smoke anything.