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535is Stalling out when it rains

Posted: Jan 24, 2023 1:18 PM
Twice now my 535is has stalled out after driving in the rain. Today drove thru moderately heavy rain, got to my destination and then it restarted but died within a few blocks. Sounds kinda as if its trying to start without the AFM hooked up, but will rev a few times then die. Last time it happened, 3 mos ago, went back the next morning and it started and drove fine til today. It does have a bit of a rough idle, but nothing that has been a major problem. 183k miles, engine clean, no leaks, new plug wires, injectors, distributor cap and rotor. No sign of moisture anywhere near any of those things. Shield is in place for the sensors on the transmission and they appear to be dry from my view point in the engine bay (they haven’t been replaced in the year I’ve owned it).

Re: 535is Stalling out when it rains

Posted: Jan 24, 2023 7:02 PM
by Shawn D.
I see it's your first post -- welcome! Please read and heed the Forum and Tech FAQ sections.

Thanks for doing an excellent job of describing what you've looked at and done. Many folks new to the board don't do that, so thanks!

The next thing to consider is a wet oxygen sensor and/or sensor wiring. Lots of folks have found those to be the culprits when issues like what you're describing have popped up. Sometimes just disconnecting the oxygen sensor works, sometimes it just has to dry out.

Re: 535is Stalling out when it rains

Posted: Jan 24, 2023 9:58 PM
by adam_poll
I think Shawn is right here that it is the oxygen sensor wiring, especially if it has the connector under the car like they were in 86 and older. You can clean up those connectors, pack them with dielectric grease and tape them up to help seal them from the weather. If it does happen again you can unplug the sensor input to the ECU at the firewall under the hood where the wiring harness goes through, you will see a single green wire with a connector right there, just unplug that and see if it clears up.