2004 BMW 325i Q&A
2004 BMW 325i Question: How can I check for vacuum leaks?
A few weeks ago my service engine light came on. So I went to auto zone a borrowed there OBD2 scan tool. The codes displayed were P0171 & P174, system too lean in bank one and bank two. Next I read up on the error codes and I checked a few things. First I checked the air filter and it was filthy. The date on the airfilter was February 2004.....looks like air filter was Never changed, so I changed it. Next I cleared the codes with the OBD2 scan tool and the next day the light came on. So the next step I took was to clean the mass air flow sensor and that did not work either....I still get the same error code :-(. Now I need to know how can I check for vacuum leaks? I see no damaged hoses. Should I take my car to the BMW dealer? I'm still under warranty until may 2010, but I'd hate to get billed for something simple to fix. They wanted to charge me $130 just to check the codes.. :-/. - MariaBMW325i
This is all likely covered under the emissions warranty, so I wouldn't worry about it. As a matter of fact, you shouldn't be "cleaning" the MAF, this could void the warranty on that part, so it's a good thing you didn't do it! Right? I would take this in to the dealer, they should address this for no charge, just make sure they inform you prior to any charges so you can decide before they do the work. - Bret Bodas
Use a propane torch (open valve - without lighting gas, of course) and SLOWLY move torch nozzle along any intake manifold hoses and duct work. You need to be upstream of the MAF (Mass air flow sensor so that you don't get a false result when the engine inhales propane gas from the air filter box or air intake). If at any point, you hear engine RPMs increase, you have a vacuum leak. At this point you can hone in on the source of the leak. This will take a little practice and patience. Disclaimer: Introducing propane into the engine bay may sound like a dangerous proposition, but in point of fact, it isn't, UNLESS you have an open flame or a lit cigarette in your mouth - be wise!! - Synectic
If your lower intake boot is torn, it is possible that your pcv valve has gone bad also. Will recommend to replace pcv valve and all hoses coming off of the pcv valve. Will not recommend if you do not have the proper tools and time to get this job done. If you have some mechanical back grounds, then it will not take you long. If you don't, will highly recommend to take to BMW dealer. Thank you P.S. Using propane is not a good idea, the best way is to use brake cleaners that you can purchase at any local automotive stores. Propane is highly combustable when vehicle is running, brake cleaner will not combust when introduced onto or into the intake side while the vehicle is running. - bmwtechmong
i had the same problem today took it to autozone and they told me it was a vacuum leak so it could be a couple thing thats what they told me so first he told me to try spraying brake fluid all around the head gasket and hoses in if the engine would start shaking then theres where the problem could be but my problem was the gas cap replaced it and light when off. - Visitor
vacuum leak i replace the air fielders boots going too the thottbod leak is louder
I have a sputtering problem that happens once or twice a week and my check engine light is on. I went to autozone and had it diagnosed as having duct tube damage caused by a large vacuum leak on en...