2001 325i p0171,p0174 and assorted missfire codes
Hello all, Well my story started with my sons 325i and the ck engine light. Yes lean bank 1&2 codes and a variety of missfire codes. I started with the fuel filter which needed replacement. I noticed quite a vacuum in the crank case.Some people said you should have vacuum and some not. Well to straighten out this mystery you ARE NOT SUPPOSED TO HAVE A STRONG VACUUM IN THE CRANK CASE. It should be very little vacuum with the oil cap off and just about nothing with the dipstick out. I have been a mechanic for many years and have very little bmw experience, however my sons 325i sure looked to me like a vacuum leak in progress. I checked the air intake tubes, the intake and every component with carb spray. No leak was found. I read once about a problem with oil separator valves. I went to bmw and dropped $62 down for one and went home to have a look under the hood. Needless to say I cant see anything that resembles the part. After searching the net I found a parts diagram and this valve is under the center of the intake manifold.The air adjuster must be removed on the intake manifold along with the air box all intake hoses,the wiring harness block and unplug most ends to be able to move the block out of the way,dipstick tube,throttle body,upper fuel rail trim cover.Now you can see ths oil/separator valve,two torx screws hold it on.There are three hoses on the valve.Replace all hoses with the valve.One hose on top of the valve goes through the intake manifold and twists on. It took one hour to install that one.The middle hose goes to the left side of the upper valve cover.Squeeze them together with your fingers to release.The third hose is on the bottom of the valve and goes to the dipstick tube.That hose is the cause of all the problems because it clogs up with crank case doo doo and causes the hose to collapse under vacuum and then sends the valve off tilt and a great internal vacuum leak takes place in the crank case.After changing these parts the car is running like a pedigree once again. Allow four or five hours for this job and a cup of starbucks. I hope this helps someone,
Last edited by zatoich; 04-04-2007 at 05:42 PM.
Reason: Left out info