Accelerator Pedal Too Heavy - PeachParts Mercedes-Benz Forum

nyko46 · #1 04-15-2015, 07:51 PM

My 1984 300 SD Mercedes Benz have the accelerator pedal too heavy that I need to put force on my feet to keep constant speed.
I apply some lubrication on accelerator cable but it still no helping as I would like.
Other than lubrication, what else can be done to have a smooth and light accelerator?
Thanks

Mölyapina · #2 04-15-2015, 09:12 PM

I'm not sure what you lubed -- there is no accelerator cable in the 300SD.

Here is a recent thread on the topic of softening the pedal:

Removed Throttle Spring - wow, big difference!

nyko46 · #3 04-15-2015, 09:54 PM

Hey Jooseppi;
I lubed the cable that goes to the linkage at the top of the valve cover.
You are right, that cable is not from the accelerator.
I liked your verse from Bible.

Mölyapina · #4 04-15-2015, 10:16 PM

Quote:

Originally Posted by nyko46

Hey Jooseppi;
I lubed the cable that goes to the linkage at the top of the valve cover.
You are right, that cable is not from the accelerator.

Yup, that's the Bowden cable

. You can adjust shift firmness with it, though I don't remember exactly how.

Quote:

Originally Posted by nyko46

I liked your verse from Bible.

Thanks! I've actually been thinking lately of changing it, but I haven't settled on a replacement yet.

Skid Row Joe · #5 04-15-2015, 10:41 PM

First of all, are you sure you just don't need a new rubber foot pedal?

I wore mine out and had to buy a new one after it was 13 or so years old, and the car had 250K+ miles on the original pedal.

Mölyapina · #6 04-15-2015, 11:21 PM

Out of curiosity, what was it about the wear that made your pedal harder to press?

mannys9130 · #7 04-16-2015, 12:27 AM

Quote:

Originally Posted by Jooseppi Luna

Thanks! I've actually been thinking lately of changing it, but I haven't settled on a replacement yet.

How about Romans 13:10?

OP, it's advised to clean the throttle linkage periodically and lube the ball joints of all the connections. I have used ATF since that's what MB suggests, but this recent round I used white Lithium grease. Both work, but the main idea to to clean old crud out, and put new lubricant in. That will help a lot!

Ceristimo · #8 04-16-2015, 11:57 AM

@Jooseppi Luna
I adjusted the bowden cable on my W123 a few days ago. If you screw the nut in the cable will get more slack and the car will shift earlier (lower rpm's), and if you screw it out it will pull tighter, and shift later (higher rpm's). I could screw mine by hand, didn't need any tools.
I think you want it to where it has a tiny little bit of slack.

nyko46 · #9 04-16-2015, 06:31 PM

Today I checked the accelerator spring in the back of the engine and it is a really big spring. First I am going to clean and lubricate all throttles and linkage and see how smooth it will be. If it still not better then I will try a spring with less tension.
About the Bowden Cable, years ago, suggested by a friend who works in transmission , I made some adjustment for shifting and it worked good. I did the same as Ceristimo described.

leathermang · #10 05-08-2015, 11:55 PM

In the FSM there are specs as to the adjusted length of each of the parts in the accelerator linkages.... we have seen this problem before..... sometimes part from other cars are substituted..... or the relative distances are changed... and it changes the mechanical advantage of the pedal... it can make a lot of difference....
I would not remove the spring completely.... as I am sure it is there to provide a NON OVER SPEED situation if something breaks.....

BayouFlyFisher · #11 05-09-2015, 07:01 AM

I removed my spring almost two months ago and could not be more pleased with the results. Good luck!

leathermang · #12 05-09-2015, 08:48 AM

Quote:

Originally Posted by BayouFlyFisher

I removed my spring almost two months ago and could not be more pleased with the results. Good luck!

That is nice... it is well documented that you know more about the design of these cars than Mercedes did..... You only need to wear your seat belt just before an accident... so you can leave it off all the rest of the time....
You think they just put that spring in there to harass you ?
That is your car.... but the idea of feeling the need to post and suggest to others less than well thought out actions mystifies me.

OK... here is a LIFE RULE... not just Mercedes diesel rule...

If you do not KNOW the function of a part on a machine.... any machine....
Do not let hubris overtake you and remove it....
because it might be a safety backup part.

Junkman · #13 05-10-2015, 04:50 PM

[QUOTE=leathermang;3473380]That is nice[QUOTE]

Reminds me of an old joke.

Southern Belles were sitting on the porch.

One said "look at those nice diamond ring my husband bought me."

Response: "That's nice"

Look at that new Cadillac my husband bought me."

Response: "That's nice".

"What has your husband done for you?"

Response: " He sent me to finishing school."

"Finishing school? What's so good about that?"

Response: "Well, I used to say *%&#!!! you. But now I say that's nice".

leathermang · #14 05-10-2015, 05:12 PM

LOL.....

Maxbumpo · #15 05-11-2015, 10:41 AM

Quote:

Originally Posted by leathermang

In the FSM there are specs as to the adjusted length of each of the parts in the accelerator linkages.... we have seen this problem before..... sometimes part from other cars are substituted....

I agree with this, often some ignorant soul will try to "adjust the idle" or some-such foolishness by making adjustments to the throttle linkage. Dig into the FSM, set all the throttle linkage back to factory spec, be happy.