Hi,

I just bought a 98 audi a6, Once I start my car the revs are not stable it keeps going up and down between 1000 and 1500 rpm. The interior lights and the head lights gets dimmer and brighter to match with the rpm. I live in north dakota. It is really cold up here in the winter. This happens only as soon as i start my car uptil it warms up. Once it warms up like in 5 mins. It just works fine. The Check engine light is on as well. What could be wrong? please help.

 

any help???

 

I'd guess you alternator or battery would be the cause. Take it to autozone or advanced or someplace similar and have them do a free test. Might just need a recharge on the battery.

 

Thanks for the help. I took it into autozone. They only got one code PO411. Seems like that might be the secondary air pump, valve or *****..if im right. Do you think that this could effect the revs on start up as well or would be be just the battery like you said.

 

If it starts the problem isn't the battery. The engine speeding up and slowing down indicates a problem with either the fuel or air going into the engine. The mixture probably isn't rich enough when cold. I would take it to a dealer or Audi specialist and let them keep it overnight to see exactly what happens when starting cold.

 

If it was an air or fuel problem, it'd be more constant. OP stated it only happened for the first 5 minutes. He needs to get vag-com to see what else is going on in there. I doubt just the SAP is causing it.