Parts Catalog Accessories Catalog Tech Info Tech Forums
  Search our site:    
 Cart  | Project List | Order Status | Help    

Go Back   PeachParts Mercedes ShopForum > Technical Information and Support > Tech Help

LinkBack Thread Tools Display Modes
Old 10-29-2000, 04:52 PM
Registered User
Join Date: Mar 2000
Posts: 517
1991 300 E (M103.983) has suddenly started idling at approx. 1500-1800 rpm at startup, regardless of engine coolant temperature. Disconnecting the power harness to the idle speed valve results in a drop of RPM to approx. 750 in park; reconnect the harness and the engine idles fine under all conditions. With harness left disconnected, engine idle speed falls below specs when drive &/or A/C is engaged.

Installed a new idle speed valve, with same results: high idle speed at start-up and then drop to normal when harness is pulled and reinstalled. Fuse on overvoltage protection relay is intact. Any ideas as to where to look next? TIA.

Reply With Quote
Old 10-29-2000, 06:03 PM
Registered User
Join Date: Mar 1999
Location: Suwanee, GA, USA
Posts: 4,712
You should check the idle speed contact on the lower part of the throttle plate.
Also check to make sure that there is no binding in the throttle cable or related hardware.

The other possibility is a fault in the fuel mixture controller (air plate housing)> If any problems are seen, the system will go into limp.

A lambda tester will show a fixed percentage and can be traced this way if the fault is occurring at that time.

Donnie Drummonds
Reply With Quote
Old 10-29-2000, 09:01 PM
Registered User
Join Date: Jun 1999
Location: Surrey, Beautiful British Columbia, Canada
Posts: 750
had similar problem before. my mechanic replaced idle control valve, temperature sensor, and overvoltage relay. i believed the real culprit, in my case was the overvoltage relay. good luck.
Reply With Quote
Old 10-30-2000, 09:42 AM
Posts: n/a
I have a '89 190e, 2.6 that does the exact same thing. I checked all the same things, idle air control, idle switch, etc. If I turn off the engine and then turn it back on, it usually corrects the idle. I suspect the Overvoltage Protection Relay, but have not yet replaced it.
Reply With Quote
Old 10-31-2000, 12:15 AM
Registered User
Join Date: Mar 2000
Posts: 517
Replacing the throttle linkage microswitch (002 545 68 14) solved the problem.

Thanks for the assistance!
Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
high idle speed M110 280 G-Man Tech Help 4 01-13-2004 08:33 AM
High Speed Pinging Sounds 85 300 Tdt shear2001 Diesel Discussion 7 12-28-2003 04:04 PM
High Speed Radiator Cooling Fans Problem? 350 SDL-126 ezrider Tech Help 0 05-17-2002 02:59 PM
High Idle Bill560 Tech Help 1 04-11-2002 01:51 PM
High Idle speed merc380sel Tech Help 9 03-08-2001 04:55 PM

All times are GMT -4. The time now is 10:28 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2016, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2011 Pelican Parts - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page