X3 is acting wierd

So my X3 is behaving wierd. at idle and idle only the engine has a quiver. If I can get the RPMs up to 900 it stops.

3.0, stick

The check engine light is giving me a misfire in 2,3,4,5,6, this morning I heard a popping sound about every 3/5 seconds. you can feel the pop in the drivers side floor boards ever so slightly. If you couldn't hear it you probably wouldn't notice it.

There has been no drop in power or decrease in fuel economy. I rebuilt the alternator about 500 miles ago.

Before I go tearing into it this weekend, any ideas?

bad coil/distributor? On light /closed throttle, youre not getting 100% juice, hence the misfire. Open up the throttle, get a bit more out of the alternator, miss goes away? Just a theory. I have just slightly more auto-electric knowledge than my left shoe, so actual mileage may vary.

DISA valve or PCV most likely.

Remove the oil cap with the engine running, if it has a lot of vacuum it's probably the PCV. Otherwise it's probably the DISA valve. VERY very common.

+1 for what cone junky is saying, vacuum leak is almost certainly the culprit. Is this an M54 or an N51/2 engine?

For the M54 the likely list is: DISA, intake boot, oil separator/ccv.

A pressurized smoke test is the best way to find the leak/leaks but you can do it the hard way too.

DISA check - remove the valve assembly, visually check for a broken/loose flapper. If flapper is not broken then actuate it fully by hand before covering the small hole on the bottom of the solenoid. Release the flapper, it should maintain its position, if it flaps back open slowly or quickly you've found the leak.

DISA valve check video: http://youtu.be/lqYVFIq4NB8

Lower intake boot check - Use a flashlight and mirror to check the lower intake boot extension which joins the idle valve. You can also just reach down and check for boot cracks.

CCV check - these will occasionally seep oil, oil seepage always indicates a vacuum leak.

Let me guess, this started when the mornings got cold? If so, CCV is very likely (assuming M54). The system can fail in a variety of ways, from a simple vacuum leak to sucking all the oil out of the pan in a very few seconds and depositing it in the intake manifold. The whole thing should be changed no more than every 100k miles, including all hoses; the distribution piece should be cleaned thoroughly, and the dipstick guide tube (which contained the drain) should be replaced as well (updated part, not nearly as prone to clogging). If you do your leaking oil filter housing gasket at the same time you'll have better access.

02Pilot wrote: Let me guess, this started when the mornings got cold? If so, CCV is very likely (assuming M54). The system can fail in a variety of ways, from a simple vacuum leak to sucking all the oil out of the pan in a very few seconds and depositing it in the intake manifold. The whole thing should be changed no more than every 100k miles, including all hoses; the distribution piece should be cleaned thoroughly, and the dipstick guide tube (which contained the drain) should be replaced as well (updated part, not nearly as prone to clogging). If you do your leaking oil filter housing gasket at the same time you'll have better access.

my oil filter gasket isn't leaking

Flight Service wrote:

02Pilot wrote: If you do your leaking oil filter housing gasket at the same time you'll have better access.

my oil filter gasket isn't leaking

Yet

ansonivan wrote:

Flight Service wrote:

02Pilot wrote: If you do your leaking oil filter housing gasket at the same time you'll have better access.

my oil filter gasket isn't leaking

Yet

Yeah. All M54 OFH gaskets are leaking - some just haven't found a way to express it.

So what's the score sir? Who won the vacuum leak trivia quest?

No one yet, had some stuff come up this weekend. Should get to it soon. I will let everyone know when I gitr' done