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E36/7 Z3 (1996-2002)
E36/7 Z3 Roadster, Z3 coupe, Z3 M Roadster and Z3 M Coupe talk with our gurus here.

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  #1  
Old 05-14-2017, 08:11 PM
ackwik ackwik is offline
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Location: Northern Ohio
 
Join Date: Oct 2010
Posts: 7
Mein Auto: 2000 M Roadster
Problem with high startup RPM

I have a 2000 MZ3 with 45000 miles which I recently brought out of winter storage. All seemed well and it was running (idling) fine so I pulled it back in the garage since I didn't have the time for a good run.

That was a few weeks ago, today when I went out and started it up for a drive, the idle went straight up to around 1500 which didn't seem right for 70 degree weather but I let it run, about 30 seconds later I blipped the throttle which I thought would bring it down. Well it didn't and it started to slowly increase to 2000 I blipped the throttle again but it continued up so I turned it off. Did retry to start a few times with the same results.

I checked all the throttle cables and they all seem to be returning correctly and have some play, so I don't think that's the problem. Went in and checked the forum and Internet but couldn't find the exact same issue, but did find related idle problems with vacuum leaks, idle control valves (ICV) throttle position sensors (TPS) and temp control switch. So i have looked over as many of the areas I could see for vacuum leaks and didn't find anything.

So out of curiosity I unplugged the ICV and started the car, it idled just fine around 700 without a single miss, revved it up a little and it came right back down, plugged the ICV back in and it went right back to 2500-3000. From what I've read this means it maybe ICV related but may not be the ICV?

I need to do some more investigation, but would like to know if anyone has ever see or had this problem and can point me in the right direction.

Thanks guys!!!
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  #2  
Old 05-16-2017, 06:56 PM
ackwik ackwik is offline
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Location: Northern Ohio
 
Join Date: Oct 2010
Posts: 7
Mein Auto: 2000 M Roadster
Update

No responses, must have everyone stumped?

Thought I'd give an update and ask more questions. Talked with a friend that talked with some BMW techs and they all seemed to think it is a stuck idle control valve, especially since it's a garage queen. But before I take it out I thought I'd do some more research.

I bowered a scan tool and did some checking, there were no codes either current or pending, but when I did a live check with the key on engine off the TP% was at 71, and when I slowly depressed the throttle it went to 99 before I even got half way down?

First thing I did was to actually check the throttle position and it was completely closed even though the scan tool showed 71?

Not knowing exactly what the number should be I check my truck and found it to be 14 with the the key on engine off and went to 90 but that took the pedal to the floor.

Could this mean it's the throttle position sensor and not the ICV? Any other checks you can recommend?

Thanks!
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  #3  
Old 05-17-2017, 07:21 PM
ackwik ackwik is offline
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Location: Northern Ohio
 
Join Date: Oct 2010
Posts: 7
Mein Auto: 2000 M Roadster
Another Update

So today I recheck the TP% on the scan tool and it still read 71%. I removed the screws and the TPS, then rotated the inside with a screw driver, the TP% on the scan tool followed down to 15% and up to 99%. Seems to work OK and smooth?

Check the throttle plate and it was closed, reinstall the TPS on the body and realigned the holes and the TP% read 71 again, rotated the TPS on the body until it stopped, approximately 15 degrees and the TP% read something like 15.

At this point I decided to start the car, it idled perfect and I could raise and lower the rpm with the throttle pedal so I turn it off. Turned the ignition on with the engine off and read the live TP% it still read 15 and I could take it up to 99 with the throttle pedal at the floor.

When it idled perfectly, to me, this means that the ICV is functioning properly and there is no vacuum leak? But something is still wrong with the TPS? Decided to see if I can take the TPS apart, broke the clips that held it together but did get it apart.

Everything looked good and I did not see any moisture or debris even under magnification. Put it back together and reinstalled it on the throttle body, not sure what I did or what happened but when I lined up the holes the TP% was at 15? So I locked it down with the screws (the TP% fluctuated some) but it settled in at 15.

Started the car and everything acted like nothing was ever wrong so I let it warm up and did some revving all is good. I will be getting a new TPS, but I'm still confused as to what was really wrong, did I fix or just get the ECU back in sync?

Will take it for a run once the new TPS is in and the idle is steady again. Will let you know!
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  #4  
Old 05-22-2017, 01:19 PM
ackwik ackwik is offline
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Location: Northern Ohio
 
Join Date: Oct 2010
Posts: 7
Mein Auto: 2000 M Roadster
Yet another update

Installed the new TPS Saturday morning, RPM was right were it belong. Don't know if its just me or the new TPS, but the car seems to be idling the best it ever has, not even a miss! My schedule and rain still would not allow me to take the garage queen out this weekend for a run, which I still really need to do.

I did bring the old TPS into work today and looked at the inside using a Mantis at 6X, its a microscope our electrical guys use to inspect PC boards. We noticed some really small droplets of fluid that looked and moved like water? Snapped it back together and retested it for flat spots with an ohmmeter, all seemed OK throughout the full range.

After thinking about the fluid, and if it is water, maybe I introduced it while rinsing the engine compartment, something I like to do when the engine compartment gets dusty?

Note to self; be more careful with the hose and water pressure!!!
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  #5  
Old 05-22-2017, 03:14 PM
vintage42's Avatar
vintage42 vintage42 is offline
BMW CCA 1405
Location: Louisville, KY
 
Join Date: Jun 2007
Posts: 3,760
Mein Auto: 1997 BMW Z3 1.9 5MT
Quote:
Originally Posted by ackwik View Post
... 2000 MZ3 with 45000 miles which I recently brought out of winter storage. All seemed well and it was running (idling) fine so I pulled it back in the garage since I didn't have the time for a good run. That was a few weeks ago...
Quote:
Originally Posted by ackwik View Post
Installed the new TPS... did bring the old TPS into work today and looked at the inside using a Mantis at 6X... noticed some really small droplets of fluid that looked and moved like water... maybe I introduced it while rinsing the engine compartment, something I like to do when the engine compartment gets dusty?...
So right after taking the car out of winter storage, you washed the engine?
Not to turn this into a engine cleaning thread, but I use a spray made for motorcycle engines, S100 Total Cycle Cleaner, made for electrical connections.
http://www.s100.com/s100_tcc.htm
I cover the alternator and big electrical connectors (squids) with tinfoil, and rinse with a fine almost misty hose spray that won't penetrate. Then use a leaf blower and start up immediately.
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