Missing Buffer or Misaligned linkage

[w113abudhabi]

Hello

My engine is not downshifting properly and my mechanic has worked through a few things. One question please: should there be a buffer to enable the accelerator pedal to engage the kickdown switch? I am guessing that either I have a missing buffer or a misaligned throttle linkage and probably the latter.

All comments gratefuuly received.

Many thanks,

Pierre

[ja17]

Hello Pierre,

The kick down switch should have a small rubber/plastic button on the end of the unit, which contacts the pedal when depressed. If the accelerator pedal does not reach the kick-down switch then the engine linkages could be set incorrectly. Check out "The linkage Tour". If the accelerator pedal does contact the switch, then the switch could be faulty. Check it with a test light. If both of these check out OK, then check the engine timing. Engine timing can cause a change in engine vacuum. Kickdown may not occur if engine vacuum is not correct.

[ctaylor738]

In addition, you may need a modulator pressure check and/or adjustment.

[Benz Dr.]

I find low engine vacuum will affect shift quality. The better your engine vacuum level is the better it will up shift. High vacuum will soften up shifts - the higher the vacuum the softer the shift will be if you lift off the throttle to affect an up sift. When you have WOT and the engine shifts into next highest gear, the shift should be quick and firm so that the trans doesn't flare as it's shifting. The modulator will self adjust according to RPM, load, ( vacuum ) and throttle position.

[w113abudhabi]

Many thanks to all those who responded.

Please find attached pictures from my car.

You will see the temporary solution that the mechanic has strapped onto the throttle pedal to ensure the kickdown switch engages. He reports it is now functioning well with the assistance of the temporary and unsightly solution. Based on JA17's response am I right in thinking that my issue may well be that there is a plastic button missing from the kick down switch which may have resulted in the gas pedal failing to engage the switch?

Don't worry about the dirty carpets - they are covered in my plan!

[ja17]

First make sure all parts are in place, looks like the small plastic cap on yours might be missing. After confirming this and installing any missing part, the pedal height is adjustable vial the engine compartment linkages. The linkage tour should shed light on this if you have an issue there.  The two possible places to adjust the pedal height are the slip adjustment on the firewall linkage (near the booster) look for the spring and 13mm hex head bolt. This is a slotted connection. Remove spring before any adjustment or the linkage will adjust itself too far when the bolt is loosened. In addition changing the length of some of the primary engine linkage rods (before the cross-over rod) will also change the pedal height. In any case after any linkage adjustment for pedal height, you should confirm two things:  the accelerator pedal engages the kick down switch when fully depressed, and the intake venture is all the way open when the pedal is fully depressed (if not, you are not getting full throttle power).

[w113abudhabi]

Thanks Joe. It would be very helpful to see photos of the equivalent area from an automatic with well functioning linkage and  kickdown, if any users have time to share theirs.

[w113abudhabi]

Can anyone confirm if the automatic 280SL should have the cover shown in the below link:

http://pages.ebay.com/link/?nav=item.view&alt=web&id=181292182427

[wwheeler]

Does anybody have a picture of the plastic cap on the kick down switch? My W111 never had one and has just the metal stem protruding like the above pictures. My kick down works fine, just curious about the cap. Is it just a W113 part?