S50 Vanos Solenoids - lumpy idle

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  M roadster S54
Location: East London/Essex

S50 Vanos Solenoids - lumpy idle

Post by Gazza » Mon 01 Jul, 2013 10:29

This description is taken from the thread by Mad Max

Then the solenoid saga began... I was driving along one day, stopped at some lights and noticed that I had an idle that was lumpier than school dinner custard! When I got into work I checked the obvious air pipes but couldn't find anything. I rung my local indy who said "oooh, that sounds like what happened to my old Evo - it was the exhaust solenoids!". Fearing the worst I popped in on my way home from work and my fears were confirmed when the Auto Logic brought back the exhaust advance solenoid. Queue the VANOS test and every single one clicked bar the exhaust advance. Gutted!

These little buggers are the exhaust advance and retard solenoids. They are about £600 from BMW for the pair! Still, I didn't pay that, I spoke to a few people (Enda!) who pointed out that the main cause of the failure is a little bit of solder on the solenoid. Off to work I went, took the car apart in the car park and then had my soldering-ninja guy at work do the work... checked it on a meter and it was perfect. Reinstalled it and... that's one creamy idle! :)

Happy... for now. I was driving her the next day and she felt underpowered below 4k rpm, after that she was fine. I ran a diagnostic on the old laptop that I've got at home and what did it bring up? VANOS solenoids! Only this time it was the intake one... annoyed by this and owning a soldering iron I decided that I could do what I'd seen my mate do at work the other day, and I did. I took the intake solenoids out, soldered them up and checked on a meter... perfect. Great, so I put the VANOS back together and went for a spin... she felt great for 100m but then after that the performance went again! Back home, another diagnostic and it flagged exactly the same. I started to take it all apart again, but then I noticed that the intake solenoid was unplugged - how odd, I'd just plugged it in minutes ago, so I took off the black cowl underneath and plugged it back in, tightened the bolts up on the cover, gave the plug a wiggle and it fell back out again!

It turns out that if you over-torque the nuts on the black plastic cover it flexes and presses on the release for the intake plug! My own bloomin' fault..! Haha!

"Understeer is when you hit the wall with the front of the car, oversteer is when you hit the wall with the rear of the car. Horsepower is how fast you hit the wall and torque is how far you take the wall with you"

S54 M roadster Image, BMW Z1, BMW M3 CSL, Mustang Fastback


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