Bad idle and misfires out of nowhere, no CEL. Thermostat?

[agart]

Last night I was coming home and after about a 40 min ride I got into my home town. Out of nowhere my idle gets really sloppy, I start backfiring like crazy and at one point the car even died while idling. I can't accelerate normally anything over I'd say 10% throttle causes the car to buck/misfire as if it has antilag. No CEL but I got the following codes:

Trouble code 2 ; P0219 Engine Overspeed Condition
Trouble code 3 ; P1292 Map Controlled Engine Cooling Thermostat -F265- Open circuit

Trouble code 1 was system low voltage which I'm going to chalk up to the car stalling. I haven't done any changes to the car recently. We had heavy rain yesterday but everything that should be sealed is as far as I know, including the ECU tray. I also got gas before heading out on the trip but I figure if it was bad gas the issue should've started sooner than that. Looking around at thermostat threads it seems a common symptom is a car that takes a while to warm up. My mother has a B6 as well and I've noticed that hers warms up significantly faster than mine for a while now. Did the thermostat die or is it something else? Any other tests I can run to check?

[MTS]

Don't think a thermostat would cause misfiring and a stall. Odd that a CEL didn't hit, at least to say what cylinder misfired. Hmm???

[Dubsport Inc]

I would look for a huge vacuum leak...

[agart]

I would look for a huge vacuum leak...

Yea I didn't see anything first time around, I'll look again though.

[SlickFix]

Can the coolant temperature sensor go bad without a code or CEL? Sure sounds like that could be a possibility.

[agart]

Can the coolant temperature sensor go bad without a code or CEL? Sure sounds like that could be a possibility.

It can, to be honest I ruled that out because I had one go less than 2 months ago... Add that to the list of possibilities. At least that one is cheap to test.

[SlickFix]

You might want to clean your MAF, too, while you're eliminating cheap possibilities.

[agart]

You might want to clean your MAF, too, while you're eliminating cheap possibilities.

MAFless, even cheaper!

[ECS Tuning-Audi]

Maybe consider doing a compression test to eliminate the possibility that you popped the head gasket.

Jason

[Dubsport Inc]

suction pump seperated?

[agart]

suction pump seperated?

Don't have that either, did a PCV simplification.

[agart]

So not the CTS and I still can't find any vacuum leaks. When it starts up it goes right to 2k hovers for a second than drops and stumbles around for a while. If I try to rev it stumbles even harder and stalls out. Going to try a compression test in the morning and if that yields nothing I'll follow the DTC and get a thermostat.

[agart]

Replaced the thermostat and nothing again. Although the car does warm up significantly faster. I drove around a little to get a better idea of the issue though; On cold starts it'll stumble and stall a couple times before it's ok. Then it'll idle a bit rough but nothing too noticeable. When cruising if I get on it it'll stumble/misfire for a couple seconds and then build boost like normal. Rev-matching is hit or miss, sometimes it'll be fine, others it just won't have it. Starting to think I should check my exhaust as these are similar symptoms to what I had when I first installed the BT setup. I also managed to pull the wiring on the IAT sensor changing the thermostat and I got a code for that when I restarted. Got a replacement plug from the local junkyard for free but the code still won't go. So add that repair to the mix. Hate when my patience gets the better of me. Going to smoke test hopefully later today and we'll see how that goes.