Engine revs up to 2500 RPM with a/c on - BMW Forum - BimmerWerkz.com
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#1 (permalink) Old 09-13-2007, 07:44 PM
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Engine revs up to 2500 RPM with a/c on

1990 E30 M20

This just started. Any ideas appreciated...
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#2 (permalink) Old 09-16-2007, 02:32 PM
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It's possible that you have a bad idle air motor. Does it idle correctly other wise?
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#3 (permalink) Old 09-16-2007, 09:39 PM
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It Idles high (see other post) 1500 RPMs initially, then 1000 after a few minutes. Problems could be related I'm sure.
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#4 (permalink) Old 09-19-2007, 07:58 PM
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Anyone have troubleshooting ideas?

Thanks...

Steve
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#5 (permalink) Old 09-24-2007, 11:59 AM
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I checked the ICV for proper voltage and operation per Bentley's. I've also checked the TPS for continuity. Both systems seem o.k. to me. I'm not sure where to turn next.

The idle is a LITTLE high. 1000-1100 after warm up. Of course, I don't have a tach so it could be gauge error.

Last edited by snpower; 09-24-2007 at 12:29 PM.
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#6 (permalink) Old 09-24-2007, 12:59 PM
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90% sure your idle switch is either not adjusted correctly or has gone bad. My car did the same thing last summer, I had to remove the throttle body and adjust the idle switch then everything went back to normal. Also, it is not a TPS as it does not read any throttle position other than closed/idle. All it does is tell the DME if the throtle blade is closed or off idle/open.
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#7 (permalink) Old 09-24-2007, 01:34 PM
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Well I don't know why they call it a TPS if it isn't.

Since continuity is O.K. I would guess adjustment would be in order...
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#8 (permalink) Old 09-24-2007, 03:27 PM
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Quote:
Originally Posted by snpower
Well I don't know why they call it a TPS if it isn't.

Since continuity is O.K. I would guess adjustment would be in order...
It shouldn't be listed or refered to as a TPS, if it is that is not correct for the M20 idle switch. When the switch is adjusted correctly you will hear a click from the switch just after the throtle blade starts to open. It should be in the bently on how to adjust the switch.
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#9 (permalink) Old 09-24-2007, 03:54 PM
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Ok I have continuity as the blade starts to open but nothing when the blade is within 10 degrees wide open. I tried adjusting the switch but to no avail.
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#10 (permalink) Old 09-25-2007, 11:48 AM
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Ok, try this. With the car idling hit the idle control valve with the plastic end of a screwdriver, if the idle changes the valve is bad.
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#11 (permalink) Old 09-25-2007, 12:31 PM
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Ok. As soon as I get a new crankcase ventilation hose I'll try this and see. Thanks for the tip. More banging is always a good thing!
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#12 (permalink) Old 09-25-2007, 05:01 PM
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Done!!

Ok as soon as I reinstalled the adjusted throttle switch and new crankcase ventilation hose, the idle dropped to 700 rpm's and 800 rpm's with the A/C on (if that). The hesitation on acceleration is gone as well.

There's just a tad of a sputter left that I hear in the exhaust. Maybe clogged injectors... that's a topic for another thread.

Thanks for all of the valuable help. Hopefully I can start helping others out soon.
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