ahesq

After leaving my car for about a week, I noticed that when first started, cold start was not enabled and the engine just ran at hot idle speed. When I switched it off and then restarted, cold start became enabled.

Only happens if car is left for a week or so.

Any ideas?

Chino075

Yes, the latest ECU update does that along with screwing up how it drives when transmission is in S mode.

raudiace4

What I've noticed is if you keep your foot on the brake pedal firm while starting, it's going to do the loud cold start then reduce to normal idle. If you get your foot off the brake quickly after starting it starts and immediately goes to normal idle.

user33

Wonder whether it's an attempt to reduce engine wear due to oil being completely drained off cylinder walls after an extended period ... or something related to battery discharge after an extended off period (just postulating).

My individual mode uses Sport drivetrain setting and I noticed that the latest update caused an intermittent abrupt/hard downshift into 1st when coming to a gentle stop ... at first (pun intended). However, it "trained out" after a few hours of (mixed city/highway) driving and is now back to only downshifting to 1st when the car comes to a complete stop (i.e., as it did before the update). On the plus side, it seems that the transmission is now smoother in city traffic. From a short test in Race mode, that seems to be the same (i.e., still wonderful). Oh, mine is a 2016 C63 S, so has the 7-speed transmission.

gOt BoOsT

Mine does the same thing on the very first start when I get back every other week for work. After that initial startup it functions normally which is odd, but whatever

Xec

Seems like this is no longer the case on the 2019’s. First start-up in a month today and the car cold-started normally.

Chino075

My abrupt/hard downshift into 1st still happens even after I drove the car 500+ mi right after the latest ECU update. Another thing that happens is after the transmission is warmed up (200F) it stays on 1st gear until 4-5k rpm before it shifts to 2nd gear when just going slowly. This never happened as it would shift at around 3k, unless I'm stepping on it hard. All other modes C/S+/R is fine, only S and I have a 2018.

right_mr

only recently have I not been driving my 18 c63s. indeed when left on the drive for a week or so, when I first start it up, it goes into a sulk and doesnt idle at the cold start revs of approx 1.2k, it does around 0.7k or so. poor car, I feel guilty walking past it every day and not driving it

seems like it is engineered to do that for one or more reasons ... I call it sulk start.. note not to be confused with the facelift "emotion start"

Pete H

As your battery gradually loses its charge in a year or two... this will begin to occur

ahesq

What would the battery have to do with it?
The car cranks just fine with plenty of juice.
It's just the cold start that no longer is enabled after a few days.
Turn it off immediately, and then start it again and cold start then is enabled.

Pete H

Search the forum, it's been covered before. Battery and lost Ecu time data is a possible cause.

ahesq

Can you please point me to the forum thread?

I searched and nothing came up.

Thanks