Car: rough idle cold weather start up only

Factual Questions
1

I own a 2013 VW Scirocco R, automatic, 2.0L TFSI (ea113), 68k km, and it has been tuned by the previous owner (APR Stage 2+).

I’ve owned the car now for 2.5 years. It’s been fine other than having some loose screws leaking oil under the turbo once and a connector piece that came undone and threw a fault code (got that fixed).

But what I noticed was only during the colder weather, my morning startups would have this intermittent rough idle. It goes something like this: start up engine, idles fine for about 7 seconds, then for 3 seconds it sputters like it’s about to die, then it smooths out for 7 seconds again, and then it sputters again for 3 seconds, smooths out for 7, sputters for 3, until 60-70 seconds has passed in total and the idle is smooth and normal as always. It’s ALWAYS 60-70 seconds when I time it. It’s either time dependant or temperature because 60-70 seconds is also how long it takes to see my digital coolant reading hit 20 C (celsius). It always idle fine once it hits 20 C or 60-70 seconds, whether it is -10 degrees celsius mornings or chilly 12 degrees celsius mornings.

It only happens during the chilly/colder weather season. During the warm/summer season, no rough idle issues upon startup.

I also have a VCDS software and right now no codes come up. The only code I had in recent memory was a P0441 code which was for an EVAP issue (incorrect flow, intermittent) and the shop I took it into just replaced my charcoal canister. I don’t think they replaced or checked my EVAP purge regulator valve. So I don’t know if it could be that as the issue for my cold morning starts. I’m also running long term fuel trim RICH at about -15 to -18% but no codes yet.

My only guesses are:

  1. leaky fuel injector

  2. EVAP purge valve (clogged or stuck)…but i don’t have the problem of starting the engine after re-fuel /
    top up like I have read most people have when it’s the EVAP valve issue. My car starts fine after fueling
    up.

  3. Idle Air Control valve

  4. Idle Speed Control valve (just because sometimes when I start the car, it cranks and starts up really fast like it should or takes a little longer than it should and sounds kinda dry like it didn’t get a powerful spark or enough fuel and then the rpms hang low for 3 seconds or so and you can hear the engine is on but not turning much like it’s just hanging on and then it will get up and going to normal rpms).

Now, I don’t have this issue after the car has been warmed up and driven. If I park and restart the engine 30 minutes later or even 2 hours later, it starts up just fine. It’s only when I leave it parked overnight or during the day for 8 hours or so. I’m guessing it is temperature dependant…something about the temperature (whether it’s a part that needs to warm up like the CC or a sensor that needs to reach a certain threshold like 20 degrees celsius before something can kick in and work properly). That’s what it seems like to me.

I need some advice and help because it seems I have so many different answers (others said maybe MAF (but I cleaned it), vacuum or boost leak (I tend to think this could be ONE of the issues, but I tried a smoke test and couldn’t find a leak but I swear when I drive and enter boost, I can hear a lot of air), Diverter Valve, or HPFP.

It is a GDI engine so I suppose carbon build up could be an issue but don’t know if that is what could be causing this. Again, since it only happens in the colder weather, it’s very specific and I rule out whatever issues that should also affect the car in warm weather. It has to be something that only is affected due to lower temperatures.

Any guidance or advice would be appreciated!
Note:
new coils and sparks plugs (about 1 year), changed fuel filter, and regular oil changes, and new charcoal canister.

2

How old is the battery? They do not last forever, and get worse as the weather gets colder.

3

My theory is a vacuum leak. Until the 02 sensors heat up, the car runs off a predetermined air fuel ratio without monitoring or adjustment. After they warm up, the car then starts monitoring the fuel ratio via exhaust. It can then compensate for a small vacuum leak by adding extra fuel to account for the extra air, which will smooth out the idle.

The car will remember these adjustments needed so it can begin compensating for it immediately after the sensors warm up. If you disconnect the battery it will lose these settings and have to relearn them. One reason your car can run rough a few minutes after changing the battery.

Just my two cents.

4

Thank you for the reply. Good question. I actually do not know. I bought the car 2.5 years ago used so it very well could need a change but I don’t think I see any other related symptoms to a dying battery. I could be wrong. I’ll look into that.

5

Thank you for that suggestion. As I do think it’s related to temperature, it sounds like this could be a good possible cause.

I also noticed that each winter (this is the 3rd one), it seems to get worse. The rough idling was present in the 1st winter but wasn’t that pronounced. The 2nd winter it was noticeable and I experienced my first “shut down” if I tried to drive the car right after starting it up. I’d have to leave it running for about 60 seconds or until the coolant temp reading was around 20 C.

I don’t know if I’m being paranoid or if I really do hear something but I hear a lot more “air” when I drive in boost. It sounds like someone snoring (sucking in a lot of air) but I also notice a lack of power from standstill / from stop at a traffic light. The boost reads as high as 0.5 to 1 bar from standstill at traffic light and I feel lack of power even though boost is that high.