08 TT. Idles on the lower side, occasionally shuts down. I looked at different causes, i.e. fuel pump, vacuum leak.
Also at around 3K RPMS, sometimes the RPMS drop a bit, other than that it runs great, although there is a whistling sound which led me to believe its a vacuum leak.
Any suggestions would be appreciated

 

Hi,

Could be the camshaft positioner. Read the DME error messages to find out which bank.
You can swap left and right positioner (are the same) and read error messages once again. If failure swaps from one bank to the other you know its the positioner.
Regards
Hans

 

Thanks for the reply Hans.
I dont get any error messages, which is somewhat strange
Would it be the same cause if no errors show?

 

OK that's strange
I got error code P0021 (Intake camshaft positioner bank 2) and P2279 (Intake air system leak)

 

try cleaning your oxygen sensors as well.

 

Depends when it's "whistling". At cold start the air pumps might be whistling, that's pretty normal if it's stock. Not sure why Hans is trying to talk about his error codes, doesn't seem to apply to you.

Poor idle is probably either a vacuum leak as you suspect - if you have the stock center plenum check the connections on the back. One of the nipples may have cracked off. Also if you're running an oiled aftermarket oil filter the mass airflow sensors (MAFs) may be unhappy, and that would definitely cause idle problems.

 

[QUOTE=Not sure why Hans is trying to talk about his error codes, doesn't seem to apply to you.[/QUOTE]

Only for (probably unnecessary) information

 

My idle issue was MAF2. I started with a pressure test, then logged some values, then got a 5 point security bit set, removed 1 MAF at a time, cleaned with a MAF spray and on the second cleaning the idle smoothed out.

If you can log values that may help.

YMMV.

Ed

 

Hit or miss there in my experience, over oiled air filters tend to make MAFs unhappy.

 

The other test would be a pressure test. While not fixing my idle drop problem, I did find a rubber elbow to the turbo actuators that had a split. I think it would be a good initial step for you.

Ed