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1998 BMW 528I Engine Light On with P1188, P1189, P0173, P00170 Codes - Vacuum Leak & Poor Running Symptoms

Model: 98 BMW528I Fault Code: P0170 Posted: 2013-06-19 14:52

Hello, I'm looking for help with my 1998 BMW 528I. The engine light just came on, and before that, the car would run poorly at times—often making a noticeable air hissing sound, which I suspect indicates a vacuum leak or intake system issue. After this, there would be a small pop, followed by smooth running for a few minutes before the problem returned. Currently, the OBD2 diagnostic codes showing are P1188, P1189, P0173, and P0170. These codes point to issues with air intake metering and possible unmetered air entering the engine manifold. I usually take such vehicles to a dealer for repair, but due to my current job situation, I can't afford that right now. The car is essential as it's used for commuting to job interviews. I'm not sharing personal details—just seeking advice on how to diagnose and fix this issue. Any insights or experiences with similar symptoms and these specific codes would be greatly appreciated. Thank you in advance! Rkubiak

Related fault codes
P0170P0173P1188P1189
Comments (2)
Anonymous 2013-06-19 15:08

This issue is known to occur on certain 1998 BMW 528I models, possibly covered by a Technical Service Bulletin (TSB). One common cause is a faulty or damaged CCV (Catalytic Converter Vent) system, especially the oil separator tubing. Check all vacuum lines for cracks or disconnections—unmetered air entering the intake manifold can trigger P1188, P1189, and the fuel trim codes like P0173/P0170. While this information is general, it's based on known diagnostic diagrams from technical resources. For reference, see a related video explaining vacuum system components (theory applies to your case): http://www.youtube.com/watch?v=Eso0dgmymhY

Anonymous 2013-06-19 16:25

Thanks for the reply! I've already inspected all visible vacuum lines and don't see any breaks or damage. To clarify: when I rev the engine, I hear a loud hiss followed by a small pop—after which the car runs smoothly for several minutes before the hissing returns and performance drops again. This pattern suggests intermittent vacuum loss. Appreciate your input!