enoch861

So I have this peculiar issue:
If I let the car idle long enough it'll randomly turn off/stall.
When you try to start it back up, it struggles for a bit almost as if it's having a mild misfire but eventually starts. At that point if you let it idle the same thing will happen. So what I try to do is drive off and that becomes a challenge because the car decides to stall 3-5 times after which it drives just fine and the issue never comes up again for a while. In the last year this has only occurred a grand total of 3 times. So it's not something that occurs very often and I haven't been able to find a pattern of it. Last time it happened was when I updated my MMI a few weeks ago.

This issue only happens once in a blue moon so I haven't looked too much into it, but I have no CEL's and the CEL doesn't flash during start up so it's not misfiring. Also during idle, there is a very slight vibration/hesitation and once the hesitation gets worse is when the car randomly stalls. If I hit the gas to about 1000 RPM it's very smooth, but below 1000 RPM, it goes back to being semi rough.

I'm not sure what the issue could be. I was thinking maybe the throttle body is sticking below 1000 RPM but I would assume that would give a CEL? Otherwise I'm at a loss.

I've also noticed that the cars' cranking times vary wildly. Sometimes it'll start instantly (less than 1 second crank) while other times it'll take 2-3 seconds and these are when it's cold. Any rhyme or reason to that?

roylok

First thing that comes to mind is the fuel delivery system. Bad gas bought from your regular gas station? Fuel filter might be causing that and not trigger a code. Has it been changed?

enoch861

I was thinking that too.. but wouldn't that have an effect on everything else?
Fuel filter was changed last year after the 2nd time it happened to make sure that wasn't the cause.
I don't think it could be bad gas but that's possible. It would be difficult to determine though since I never let the car idle nearly as long all the time.

drooskii

I had a similar problem, died a few times at low speeds, and it took forever to start after a fill up. I replaced the purge valve and it went away.

enoch861

Purge valve? What's that?

I did remove the throttle body this weekend and cleaned it up a bit. Car now feels a bit better and idles a bit more smoothly.. could be placebo though.

raj99

https://www.audiworld.com/forums/a6-...3-2-a-2825901/

Buy Purge Valve (N80) - 06E906517A by Genuine OEM | Europa Parts

enoch861

Hm... I'll replace it and see if it fixes anything.
But shouldn't I at least be getting a CEL?

roylok

Throwing parts at issue sucks! Owners manual says that the car should not be left idling for a long time. Could it be something that has to do with the heat generated when the car is standing? I feel like they "know" something is wrong and they are not telling us! Trying to start it after it stalls for 3-4 times sounds like it is starving for gas though. It might be the purge valve, or the fuel pump not supplying enough pressure. Why there wouldn't be a code is a mystery to me!

enoch861

Hahaha, does the manual really say not to leave the car idling for a long time? This might actually be the first time I crack open that manual to see this for myself.
I would think that it's also starving for gas, but shouldn't I also have issues accelerating and stuff? I mean, this is an issue that only occurs once in a blue moon. So it's not something I can "readily" produce although I'm scared to try and reproduce it since the starts seem really hard.

haloguy628

Check for vacuum leaks. Your car is exhibiting classic behavior if there is leak in the vacuum circuit. If you can scan the car look for lean codes.

Another thing you can check is the gas cap. If it's not venting properly it could cause similar symptoms. Same for the oil fill cap.