Hesitation / stalling .............1995 525iT/ E34/ M50/ chassis # GD26133

[budshaw]

Car was running great. Parked for 2 hrs, then would barely start, and would die when given gas. Check engine light came on. Would finally stay running, drove 200 mi home. Stomp test threw code for mass air flow sensor. After replacement.........no change. Car is still very hesitant when starting from a stop and will completely stall if the pedal is feathered or lightly tapped .Also, for the past 2 months low oil warning has been on though level is fine. Any relation? Also, I had pulled up back seat to retrieve seat belt right before this all began. Wife swears this has a connection. Spent two hours reading related threads and honestly don't know where to begin. Crank position sensor, oil level sensor, fuses (1st thing I checked), relays, fuel issues, oxygen sensors, etc. I recently acquired an electrical tester but in all honesty, don't really know how to use it. How can I get to the cause of this problem with my limited expertise?
Any help will be greatly appreciated.
Thanks,
budshaw

[genphreak]

On a late M50 this is probably flooding.

Oxy sensor may well be bad- but you could also be suffering from a an intermittent/under-spec fuel pump problem. Quite common too.

Other things I'd look at if these don't fault when properly tested or replaced.

Remember that on there are many things that wear, and many things will make a difference. Always best to test the items you plan on replacing before doing so so you can isolate root cause. But the Oxy sensor is something that is rarely done, can save you money even if it is still working after 100k or so and can be had very cheap and swapped out in 20mins by any shop with a hoist.

[budshaw]

thanks for your input. A couple questions................Can the fault code ever be wrong? I mean why would 1215 (air mass sensor) keep coming up if it was not faulty? After I installed it is there a follow up or reset procedure? Also isn't the oxy sensor threaded into the exhaust manifold/pipe? Couldn't I replace it myself?

[Dave M]

thanks for your input. A couple questions................Can the fault code ever be wrong? I mean why would 1215 (air mass sensor) keep coming up if it was not faulty? After I installed it is there a follow up or reset procedure? Also isn't the oxy sensor threaded into the exhaust manifold/pipe? Couldn't I replace it myself?

Yes and yes. Not sure why, but fault codes can be wrong and should be used as guides. Depending on how long your O2 has been in there, it can be a relatively quick job. I've done it on my M50 in < 1/2 hour on a gravel laneway with one side jacked up.

Dave

[genphreak]

Best to consider fault codes as symptomatic first, causal second. All they tell you is that at some point, the device identified was working (or is likely to have been working) outside its range. The cause is often upstream of the fault that got isolated by the ECU.

[budshaw]

the latest twist in this mystery is that now the check engine light only lights up when at idle. As soon as I give it gas and continue to cruise, it goes out. When I stop, back on. Is this a useful clue?

[shogun]

What about voltage? Battery light working? Idiot Light - keeps the promise of "what's in a name!" (http://misterfixit.com/idotlite.htm)
Unlock the OBC and check BMW E32 OnBoard Computer (http://bmwe32.masscom.net/johan/obc_secrets/obc_secrets.html)