Idling Problems - Any easy way to diagnose?

So, I'm having some sporadic idling problems. The issue tends to disappear after I go a few miles and is definitely worst when first starting up the car. My RPMs seem steady, then decrease and then (correctively?) increases to the steady point and then the process repeats. It hasn't stalled itself out yet.

From my research thus far, there are several possible solutions:
- run a half a tank of 87 mixed with 93
- find and tighten up the loose 02 sensor (if there is one)
- ICV clean or replace
- DISA replace
- VANOS rebuild

Don't really know where to start. Is there any way to know which of these is the culprit? Your input would be appreciated. This seems to be a fairly widespread issue with the e46, so hopefully someone has run into it before. Thanks for your help!

Clean your ICV and inspect the DISA while your in there.

No codes?

No codes came up during the PPI (Only have had the car for about month and a half). Didn't notice the issue when test-driving. I had only test drove while car was warmed up. I am trying to figure out any sort of pattern when this happens and I think it happens more often when there is less gas in the tank. Could just be a coincidence. Will be filling up soon to verify. Now the question is do I do a 50/50 mix of 87/93? Supposedly the theory is that idle problems can occur when the BMW gets the same octane fuel over and over and it gets lazy and isn't recalibrating based on octane causing an idling issue...so if you run a 50/50 to force it to recalibrate and will recalibrate again when going back to premium, then everything becomes peachy. Seems like one of those crazy Car Talk answers, but who knows?

Anyway, looks like I'll probably go searching for a DIY for cleaning the ICV soon.

Ok. Check the stickied maintenance thread on the diy section.

#10


http://www.zhpmafia.com/forums/showt...e-Issues-DIY-s

HTC Thunderbolt+TT

You could try running a container of BMW's Fuel Treatment (or Lucas or Chevron) with your next fillup.

Where do you get your gas? Might not hurt to look for another station with "good" gas. I've had good luck with Shell V-Power lately.