Fuel/Air Unbalanced

[slykens]

Hello all -

I recently completed a supercharger-off service primarily focused on PCV replacement and since it was open I also did a carbon clean, replaced thermostat and waterpump, had my injectors cleaned, and I ended up replacing an injector (cylinder 6 I believe, driver's front). That service seems to have been success as I no longer have coolant loss and after 1200 miles since oil change I am still at max oil fill - never had that before, either.

After this service I am now getting a P219F - Fuel/Air Mixture Unbalanced on cylinder 4. In monitoring the engine in vagcom, I get a bunch of misfires on engine start then a random misfire here and there on cylinder 4. I monitored all cylinders today on a short drive and after about 20 minutes of driving had 1 misfire on cylinder 3 and 20 in total on cylinder 4 (13 within 10 seconds of start plus 7 from driving around). No other cylinder reported a misfire from engine start onward.

In my mind, it's one of three things: coil pack (I know, it's ALWAYS the coil pack but these are two years old with about 30k on them and no trouble prior to this service), spark plug, or injector. Since it is a pain in the balls to get to any of those in this car, I was hoping to narrow it down in vagcom but I just don't know how and google only comes up with ways to monitor injectors in pre-UDS cars. I can't find the appropriate (if it exists) value to monitor for our cars in vagcom. I also suspect it's possible the spark plug somehow got fouled, maybe with leftover walnut dust from the carbon clean or perhaps a missed piece of carbon?

Am I destined to have to play coil pack roulette or is there a method to figure this out with vagcom? I am really hoping it is not the injector as I don't have much desire to yank the supercharger again even though it wasn't very difficult.

Thanks!

edit to add - Car drives great and there does not appear to be misfires related to throttle position as several hard runs did not increment the misfire counter.

[SwankPeRFection]

Hate to break it to you, but driver’s bank front is cylinder 4.

[slykens]

Hate to break it to you, but driver’s bank front is cylinder 4.

Thank you!

Most of the documentation I could find led me to believe it was driver's rear. That also makes it easier to pull the plug and see what it looks like.

I did clear the codes the other day and the MIL has not illuminated again. Maybe I'll pull the plug this weekend.

[SwankPeRFection]

Good luck. Also, in case you didn’t know, you can just take off the nuts off the coolant reservoir and just lift it and angle it away from the valve covers. You can wiggle the coil out that way and then use plug socket > universal joint > short extension and feed that into spark plug hole then engage the ratchet on top and loosen it. That gives you enough articulation and a short enough length to easily do spark plugs on driver side and not have to worry about the coolant reservoir being in the way.

[slykens]

Good luck. Also, in case you didn’t know, you can just take off the nuts off the coolant reservoir and just lift it and angle it away from the valve covers. You can wiggle the coil out that way and then use plug socket > universal joint > short extension and feed that into spark plug hole then engage the ratchet on top and loosen it. That gives you enough articulation and a short enough length to easily do spark plugs on driver side and not have to worry about the coolant reservoir being in the way.

Thanks again. And yes on the reservoir, that's how I've done it before.