W124 Stiff accelerator pedal

[Mark Wheeler]

I am a new user just registered today and hope you can help where my local garage has failed. I have a (1991) 230TE estate which has inherited a strange problem. The accelerator pedal becomes extremely hard resulting in the car lurching forward rather a smooth take off. The problem is worse when the engine warms up, and especially irritating as the car is automatic.
The only diagnosis (by phone) has been to suggest a problem on the vacuum side of the inlet manifold. My garage and I have peered down inside at the butterfly and the flap is clean .i.e. no deposits to cause sticking, and the accelerator is completely smooth when the engine is switched off.
The throttle itself doesn't stick yet the pedal can become extremely hard to push initially then once through the (cogging/stiff) stage, behaves perfectly smoothly thereafter.

If anyone can help with diagnosis I would be extremely grateful.

Yours in anticipation.

Mark Wheeler
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[MotardMan]

Hi Mark,

I am assuming that you have lubed the linkage, and that there are no worn joints in it, as you say it is smooth through most of the pedal travel. However if it gets worse as the car warms up, could it not be the underbonnet temp warping the linkage, if it is worn? Maybe, when cold, the linkage is on the edge of the problem, but not until the heat causes the metal in the linkage to expand, does it get stiff? I'm just guessing as this does seem strange.

It is not a carpet mat or grommet in the bulkhead that is snagging the cable, linkage or pedal is it??

If you remove the air filter to allow access to the cable and linkage, let the car warm up and then operate the throttle from the engine bay, does the symptom persist? Try operating the linkage at various points through its length and travel to see if you can isolate what is making it feel stiff. For instance, operate the linkage where it attaches to the throttle bodies, where the cable attaches to the linkage etc...

HTH,

Jim

 

[maybach]

Hello
The 124 had a problem with the pivot point on the throttle pedal.
there is a modification available(not loads of money)
Speak to one of the old guys in your local M.B dealer for the part numbers
If no luck then place a post and I can get them for you
Regards
Maybach
Not all dealers are bad

 

[Mark Wheeler]

Thanks for the suggestions put forward by Maybach and Motard Man, I plumped for the mod to the pivot point which my local MB agent ordered for me. This consisted of a new accelerator pedal and clip, now fitted but hasn't cured the problem.
(I'm assuming as the throttle cable hasn't any pivot points between bulkhead and manifold, that there are no other bits to modify), can you confirm Maybach please.

Meanwhile I've been looking at the correspondence on this site and note what appears to be a similar problem posted as 'notchy throttle W124'. Possible solutions pointed to either a simple lube of the cable. (Even I can do that), or more hopeful is an adjustment relating to throttle housing and butterfly. I'll talk to my garage and let you know the result.

 

[Richard.Wilson]

Hi there Mark
The "notchy throttle W124" was mine, and having put a couple of thousand miles on the car since then, I can report that the problem has not come back.
I think this is caused by a build-up of crud and wear on multiple components, because the linkage is over-complex with too many wear points. Different wear adds up to the same problem.
However, as you may have read in the last thread, it sounds like yours is like mine (ie, it is worse with the engine running) and that lead me to look at the butterfly itself.
You can eliminate the linkage by just disconnecting it, and running the engine carefully (no filter or return cable remember) for a short while, whilst you open and close the butterfly by hand.
I think the other guys have resolved the linkage issues, so if it's that, you should find the answers in the forum.
I never did get an exact measurement to set the butterfly stop, but a clean throttle body and .002" between the body and the butterfly worked for me.
Good luck

 

[Andy]

Hi


I would agree with Richard. Problem could be a worn throttle housing. Especially if the problem is only there with the engine running. Try giving the throttle housing a little adjsutment about half a turn at a time.


Good luck

Regards

Andy @ www.mercedesservicing.com

 

[Mark Wheeler]

Hi Richard and Andy,
just a quick note to say the problem appears to be solved. The solution was as Richards, a minor adjustment to the butterfly seems to be what was required. I've only put 200 miles on the clock since the tweak, but no sign of the problem to date, And conditions have been such that it should have played up on numerous occasions since, so thanks to all for your help.
Mark