C5 RS6 - cold start issues

[vtraudt]

2003 RS6.

Having a lot of cold start issues when it is very cold in the morning.


Will have low/rough idle on start up and cannot rev motor. Does this until motor starts to warm up, then must turn off car and turn back on. Will return to normal idle, can rev and drive normally.


This morning was a bit different in that the car started at low idle but lights began to dim/turn off until the car died. Points to alternator issue?
I jumped the car. Battery voltage meter on jumper pack showed 12.5V and as the car idled longer it rose to 13.8V.
At this point the car ran normally and I was able to drive to work.


Ideas

[lswing]

Location? What is cold?

Seems like you need a new battery, is it still the original one? Cold with knock down an old battery overnight.

Don't some car computers not allow revving if it's below a certain temp to prevent damage?

[vtraudt]

Location? What is cold?

Seems like you need a new battery, is it still the original one? Cold with knock down an old battery overnight.

Don't some car computers not allow revving if it's below a certain temp to prevent damage?

Down to zero in the night, 15 during the day (Michigan).

Think some computers may intervene when cold, not sure on RS6 though.

Will get battery and alternator tested at parts store as a first step.

But rough idle is not a battery/alternator thing.

[Dmb408]

That would just be cold oil not getting to cam chain tensioners, no?

[nubcake]

That would just be cold oil not getting to cam chain tensioners, no?

No.


What does voltmeter show when you just have started the car? Does the battery light go out instantly?
Any DTCs stored in the ECU?

[lswing]

But rough idle is not a battery/alternator thing.

Do you get rough idle when warm? Do you get flashing CEL? Both of those would indicate a Cam Chain Tensioner issue...they like to fail these days.

0 degrees will knock out an old battery overnight.