At cold start (true cold start, basically the first start of the day after sitting 6-8+ hours), the car idles high per normal process, then once it levels off, it begins fluctuating a bit and will go so low it sounds like the engine is going to die.

It then normalizes after a couple seconds and will not ever fluctuate again until the next cold start. It idles perfectly otherwise.

Recently replaced the HPFP due to a leak, battery is brand new and everything else about the car works fine. This doesn’t impact drivability at all, I can take off immediately just like normal.

Video here:

 

My car does almost the exact same thing. Seems normal to me

 

(wrong thread)

 

Since it is recommended to drive off ASAP after starting I've seldom let mine drop off the high idle in its own. That being said, it wouldn't surprise me if the ECU needed to hunt a bit to find its happy place while it was getting properly warmed up. Figure the ECU is dumping excess fuel to warm up the cats which affects the O2 sensors which affect the fuel trims and the cycle isn't quite stabilized.

 

I have a .1 so not sure if this is any different for a .2 but I had a somewhat similar erratic idle and it was fixed with a new Mass Air Flow sensor

 

I've read (on posts here) that one should wait till the idle drops down after 30s-45s then drive off?

 

There has been debate, but with modern cars it is generally realized that the ECU is dumping lots of gas into the cylinders at start up in order to heat the cats. It is believed that this gas can wash the cylinder walls encouraging bore scoring. You want to get past this phase ASAP or at least use up that extra gas by using even higher rpms. This is best accomplished by driving off gently but immediately. I wait for my oil pressure gauge to respond and then drive, as opposed to waiting for the higher rpm (with lots of gas being dumped) to subside.

FWIW, 2010 C4S PDK with 172K miles. Original everything other than basic maintenance (lubricants, brakes, plugs, filters, tires, wipers, belts) and still going strong. Oh, I did need to rebuild my tensioner pulley recently and the front computer got replaced quite a while ago.

Please, any one with alternative opinions please chime in.

 

Yeah I cleaned the throttle body and inspected the MAF visually, thought about replacing it but I figured it would manifest itself regularly if that was the problem.

 

Well during lunch I just drove off once the car started!!! No more waiting for that idle to die down

 

2009 C4S PDK / 62K

To OP: Mine behaves just the same. Normal behavior.

 

+1 to what D3RP said…2009 C4S

 

Well I tried that once and spilt beer ,tacos and Clam chowder all over the centre console. I no longer try to drive away during lunch, lesson learned !

 

Well, I often reply to the wrong thread, yet feel my response is nonetheless equally irrelevent