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

LinkBack Thread Tools Display Modes
Old 12-26-2000, 08:07 PM
Registered User
Join Date: Dec 2000
Location: AL
Posts: 1,219

We own a '91 300E which has been a wonderful car. Has about 120K. Used to routinely get around 22 MPG average. It's our fifth E class we've owned.

Anyway here's the deal: When you take your foot off the gas at highway speeds, you're supposed to feel the car decelerate. But our car usually gives this strange sensation that your foot is still on the gas or the cruise is set; it decelerates ever so slightly. Except sometimes, when you take your foot off the gas and it decelerates normally. Or other times when it seems to surge; It's a subtle feeling like someone is turning the engine on and off. And yes, the throttle is in fact closing all the way; it's not hanging open a bit. None of our other 300Es have ever done this. Also, the MPG averages about 17-18 now.

The fuel is supposed to shut off completely under these deceleration conditions, until the engine slows to 1300 RPM, at which time fuel flow resumes. Our car seems to be confused, usually. It works properly maybe 20% of the time.

I have checked the switch that under the air cleaner that signals idle position of the throttle. It's fine. I replaced the speed sensor in the back of the speedometer with another I had: no change.

BTW, the car usually fails the decel shutoff test as outlined in the factory manual. But sometimes, it performs the decel shutoff just fine.

I have ruled out the following potential problems: linkage/cables, computer, idle microswitch & wiring, throttle position switch & wiring, cruise control, over-voltage relay and anything in the fuel pump relay. Maybe the electrohydraulic actuator on the back of the fuel distributor?

Ideas? This is driving me nuts! I don't like problems I can't figure out.

Michael Brewer

Reply With Quote
Old 12-26-2000, 08:40 PM
Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
Many times the micro-switch that signals the fuel computer to go into decel & equalize the fuel pressures, will not send a complete open or closed signal. Many times the ohm reading will be 20-70 ohms & the ECU doesn't know what to do. Intermittant problems can drive the computer into fixed operation mode (FOM). Other than trying another switch you really just don't know unless you are testing when it's happens.
Reply With Quote
Old 12-28-2000, 10:46 AM
Registered User
Join Date: Dec 2000
Location: AL
Posts: 1,219
Moderator M.B.DOC was exactly right. The problem turned out to be an intermittent decel shutoff switch. Thanks for helping me solve this!

Michael Brewer

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 On
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
I have info on symptoms/diagnosis of a failing/failed Fuel Pressure Regulator! azhari Tech Help 0 12-14-2003 11:23 AM
Manually adjusting fuel pressure in a 300E?? mike690003 Tech Help 14 11-22-2003 07:33 PM
280SL fuel injection question hollander_marc Tech Help 15 02-25-2001 11:57 PM
280sl fuel injection pump 63230slbenz Tech Help 3 11-19-2000 12:46 AM
300E Fuel Injection Fault Code 60 Tech Help 6 03-13-1999 03:34 PM

All times are GMT -4. The time now is 05:15 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page