2002 BMW 325xi - Rough Idle + Miss

[swood]

I have a 2002 325xi in my shop with a rough idle and miss. Checked all the basics fuel pressure, spark plugs, coils, everyting checks out ok. I pull the oil fill cap off while its running and had a huge vacume leak. Put propane in the oil fill and the idle picked up. I checked for external vac leaks couldn't find any. Is there vent valve or somthing not working correctly?

Thanks for any help, Sam

[steven kiser]

welcome to the forum. when i get into work on monday i'll look into it.

[swood]

Thanks We just signed up for Michell and I found this fourm lots of great topics here. I hope to be of help to someone at sometime on this site. The BMW is pulling a big vaccume through the oil fill in the valve cover. When you open it while its running the idle drops way down and runs really rough. When you drive it it will run ok for 1 or 2 miles then it starts to run rough and lose power. Shut it off and let it sit a few min. and the cycle starts over. I'm not really sure how the vac. system works on this. Thanks for any help on this
Sam Wood
610-360-5938

[steven kiser]

i know that taking the oil fill cap off will cause an idle issue. that's normal. your issue lies else where, the pcv system is so strong that the cap being off or dip stick out will act like a vaccume leak. if the timimg is approx the same each time i'de look towards an 02 sensor. it sounds like a open/close loop issue. if the timing is scattered i'de look towards a fuel pressure issue. are their any pending codes or is the car going into limp? see if the 02 stream bases out or freezes. i usually find that the 02's hold the answer. with a scanner watch and see if the issue happens with the loop change. i've seen internal shorts inside the 02's.

[swood]

Found the problem. This system has a vent valve under the intake that gets pluged up . This valve works like a pcv
If you do this job allow plenty of time. Its A PROJECT 8 to 10 hours

[steven kiser]

congrats and thanks for posting the fix.......................