Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Tech Help

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 03-08-2008, 10:42 PM
Registered User
 
Join Date: Jan 2006
Posts: 94
126 Idle Problems

I have a 1982 380 SEL. I have a fast idle problem. The engine runs fine and most of the time idles around 500 RPMs. However for no apparent reason, the idle will suddenly rise to 1500 to 2000 rpms. Then after a while it will drop back down to 500 then go back up after a few minutes.

I tried to kick down the trottle, no change. The thermostat has been changed, no change. I don't think its a throttle linkage problem as the idle will increase even when I don't touch the accelerator.

Any suggestions?

Thanks,
Brad.

Reply With Quote
  #2  
Old 03-09-2008, 12:03 AM
pawoSD's Avatar
Dieselsüchtiger
 
Join Date: Oct 2004
Location: Grand Rapids, MI
Posts: 15,438
These engines have a cold-idle/ idle control valve (ICV) that can fail or have issues, causing things like stalling or high/random idle. I'd check that out.
__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)
Reply With Quote
  #3  
Old 03-09-2008, 01:24 AM
Dusty-NZ's Avatar
Registered User
 
Join Date: Jul 2002
Location: New Zealand
Posts: 147
My wifes 190e did the same thing for months , then it progressed to engine stopping at random corners , then at every traffic light .

Both the Fuel pump and the OVP relays were pulled and resoldered , problems are all gone.
__________________
'72 240D
'76 300D
'88 300sel
'40 Chev pickup , the shop hack.
'73 Monte Carlo Landau, for "Super Chevy Sunday"
Reply With Quote
  #4  
Old 03-09-2008, 10:48 AM
Moderator
 
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
The v8s had a significantly different idle system from the early 4 and 6 cyl cars. The v8 idle controller's natural state is open. It has to be powered closed. It is powered by a variable duty cycle pulse. The more "pulse on" the more closed. It can be driven to 70% (70% is the highest duty cycle)closed. If it is 70% closed and idling too high false air (vacuum leaks) are occuring or the throttle isn't closed.

More commonly with symptoms such as yours the controller is deficient and releases control. This often is due to weak circuits occasionally repairable by resoldering.
__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
Reply With Quote
  #5  
Old 03-10-2008, 12:32 PM
Super Moderator
 
Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,318
The throttle has to close fully, and the throttle switch work consistnently. or the idle controller will not get a ground signal, and won't "know" that it should start controlling idle speed.

I fought with this on my 380SL, which the PO had allowed to sit for three years.

I started with a constant high idle. Found no voltage at the idle valve. Replaced the idle relay and got an intermittent high idle.

Cleaned the idle control valve, and it became less frequent.

Lubricated all linkage pivots, cleaned around the throttle stop, and cleaned the throttle body and throttle valve, (you will be amazed at what's there) and it became less frequent.

Replaced the throttle position switch, and cleaned the grounds a) at the right lower corner of the dash (you will need to check the location for the 126) and b) on the engine hoist point. Problem has not recurred.

So you have an interesting choice. It's almost impossible to tell if it's a throttle closing problem or the relay, if it's intermittent. So you can start chasing either depending on whether you want to spend money or tinker.
__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
Reply With Quote
  #6  
Old 03-10-2008, 02:11 PM
Registered User
 
Join Date: Apr 2005
Location: Northern Louisiana
Posts: 481
Chuck has a great list. I replaced my Idle control box '86 420SEL (passenger footwell) and still had occasional high idle problems; I took a clean cloth and WD-40 and cleaned the throttle body where the round air plate fits, and problems stopped. I also replaced the injector seals later, anyway. Then I found a vacuum leak in the climate control. Air leaks = idle problems. I dread replacing the rubber seals under the throttle body, but I know I'm going to have to sooner or later. There is a ground on the firewall, you can see it if you pull the instrument cluster. I did not check to see if it was accessible from below.
If you like puzzles and mystery novels and have an alternative vehicle, you'll make a great Mercedes-Benz hobbyist.
Reply With Quote
  #7  
Old 03-10-2008, 02:15 PM
Registered User
 
Join Date: Apr 2005
Location: Rockville MD
Posts: 833
It sounds like the idle control valve is working. Check the idle control module.
__________________
1985 380SE Blue/Blue - 230,000 miles
2012 Subaru Forester 5-speed
2005 Toyota Sienna
2004 Chrysler Sebring convertible
1999 Toyota Tacoma
Reply With Quote
  #8  
Old 03-11-2008, 03:28 PM
Registered User
 
Join Date: Jan 2006
Posts: 94
Thanks for all of the suggestion and the "list."

I will see how difficult it is to take out the ICV. How would I check to see if its working or better yet, clean it?

Thanks...
__________________
Dr. Brad

2003 C320 4Matic Station Wagon
2002 C240 Elegance
1982 380 SEL Star Certified
Reply With Quote
  #9  
Old 03-11-2008, 08:16 PM
Super Moderator
 
Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,318
Find a plug to seal one of the holes. Squirt injection cleaner in the other. Shake it and set it up so the cleaner doesn't run out. Let it sit for four hours, shaking it a couple of times. Dump the cleaner out. Repeat until the fluid comes out clean.
__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
Reply With Quote
  #10  
Old 03-12-2008, 12:06 PM
Registered User
 
Join Date: Jan 2006
Posts: 94
Thanks Chuck:

I've found replacement valves between $200 - $800! I'll try cleaning it....

__________________
Dr. Brad

2003 C320 4Matic Station Wagon
2002 C240 Elegance
1982 380 SEL Star Certified
Reply With Quote
Reply

Bookmarks

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 On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 02:33 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2024 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page