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Old 03-18-2002, 06:46 PM
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Join Date: Jan 2002
Location: Morristown, NJ
Posts: 2
fast idle in Park or Neutral

1992 300E - The engine idles normally but the revs go up to 1500 rpm when I shift into Park or Neutral. This happens with the engine warmed-up and cold. Should I be looking for a defective transmission contact switch feed to the idle control.
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Old 03-18-2002, 10:20 PM
Posts: n/a
Exclamation Similar Problem, sorta

My 1989 300E with 254k miles (I've clocked 94k of those) did something new this morning - it's throttle stuck. Not the pedal, mind you.

I escaped unharmed despite being on a hugely busy street going waaaaaaay above the speed limit by slipping into neutral, watching the revs climb to about 4500, mashing and holding the brakes while I came down from well over 70 and then shifting back into D.

This did the trick, but it left an impression on my amygdala ( the part of the brain that told our caveman ancestors not to hunt squirrels where the sabre-toothed tigers were last spotted).

Later in the day it did not do this again.

I wonder if this is a "known problem" on aging MBzs?

Any ideas?

Alex Wade,
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Old 03-19-2002, 01:38 AM
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Join Date: Mar 2002
Posts: 3

Hey. Can anyone help us?

I have a 1989 560SL that is having the same problems. Whenever I start the car the idle stays high unless I'm in drive. Whenever it's in park or neutral the idle stays high and continues to climb until it reaches a max of about 1700 rpm.

My electrical system is having a problem too. Some of the warning lamp functions have gone out; such as the ability of the turn signal flashers to flash. They just stay on w/o blinking when turned on. I don't know if these two problems are related.

I've never had any problems with the car before. It's in mint condition with about 55k miles on it. The only other problem I've had with it is a broken ash tray door cover.

I'm a newbie to this list. I'd really be appreciative for any help you guys could give.

Mark Sadang
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Old 03-19-2002, 09:37 AM
Posts: n/a
TO: Rallyrcr: do a search of this site for "OVP relay" - could be------
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Old 03-19-2002, 09:56 AM
Mark Herzig's Avatar
Registered User
Join Date: Apr 1999
Location: Austin, Texas
Posts: 380
There is quite a bit on this subject if you search for Warmup Regulator or additional air valve.

My understanding is that once the engine is warm, in idle you do not want any additional air introduced into the mix. My 450SL has an thermostatically controlled air slide that shuts off once the engine temp reaches a certain temperature. If the valve does not completely shut, then the additional air causes the engine to run faster...
Mark Herzig
1995 E300D 153K
1985 300D 142K (sold)
1979 450SL 122 miles (sold)
1992 500E 127K (sold)
1987 300SDL 132K (sold)
1986 300E 161K (sold)
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Old 03-19-2002, 10:50 AM
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Join Date: Jun 1999
Location: Surrey, Beautiful British Columbia, Canada
Posts: 750
a lot of possibilies

could be OVR, idle control valve, temp. sensor,
air flow meter, to name a few.

it is either you change all of the above, of see
a qualified independent shop, to properly test
each and every item. good luck.
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