The car is a 1983 280SL, long-neglected, and with a lot of needs. One is the throttle action.

With the engine off, the throttle moves easily. Start the engine and it takes a huge amount of force to move the accelerator pedal or the linkage from the engine compartment. There are no restrictions in movement and all the pivot points have been cleaned and oiled.

I disconnected the linkage at the throttle valve so that all that had to move was the butterfly, and observed a small amount of in-out play with the engine off. But start the engine, and the throttle lever appears to get pulled in hard against the housing, making it very hard to move.

I think that either the butterfly shaft or the hole in the housing housing which is passes through is worn, allowing vacuum to escape and pull the mechanism up against the housing.

Anyone seen this or have other suggestions as to what the problem could be?

TIA

__________________
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

Sounds more like there is something between the air flow meter and the throttle plate.

The throttle plate is "balanced" (meaning center pivoted) so is should move with very little effort. Either it is binding on the housing (new housing or at least a set of bushings custom installed) or there is something like a mouse nest on top of it so the vacuum holds it down.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I have inspected the throttle plate and there is no obstruction, rodent nest or otherwise, so all I am left with is the shaft vacuum leak. There are probably used units around since the recyclers take the FD's off for rebuilding and don't care much about the rest.

__________________
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

Gotta be a worn pivot then. If it goes off center under vacuum, it' won't move easily since it will be jamed up on the sides of the venturi.

Also check to make sure you aren't dragging the cruise control servo for some reason -- I've seen some pretty strange configurations of throttle linkage when someone didn't know what they were doing when they put it together!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

When I cleaned the throttle and modifeid the stop screw. would like now to get it back as nominal and correctly adjusted

Anybody knows the method to adjust the Throttle flap stop?

Attached Thumbnails

 

__________________
Keep us posted especially if your problem is solved
Present cars:
My car: E-class 420CDI, 2008, W211, V8, 180 000km

Wife's one: C-class 220CDI Sport Coupé, Euro, 2002, W203. 345 000km

Son's one: GLK class 220CDI, 2009, W204

Sold E class 260E, W124, 1988 beloved car sold after 489 000 kilometres of reliable services (engine M103, clutch and 5 speed manual gear box all original).

E-class, W210 320CDI, 2000[/B], 225 000km, Sold

Sounds like the throttle stop screw is not touching the throttle shaft allowing the plate to jam in the bore under vacuum.

The throttle stop screw looks like it should adjust idle speed but its purpose is to keep the throttle plate off the walls of the bore. The screw should be backed off til it doesn't touch the throttle arm then be adjusted up to the arm till it just moves it.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Thanks, Steve.

I did check that the lever was against the screw. So I gave the screw maybe an eighth of a turn in and that fixed the problem.

__________________
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

Thanks Steve,

Did not take the picture at idle.
The screw is touching the throttle arm and is used at idle. Adjustment is very sensitive.
This is what I am interested in to do it properly (I should have said it more explicitely). Would you know how to do it at idle?

Could not find how Bosch does it the factory.
The position on the picture is full gas.
will post one picture later.

__________________
Keep us posted especially if your problem is solved
Present cars:
My car: E-class 420CDI, 2008, W211, V8, 180 000km

Wife's one: C-class 220CDI Sport Coupé, Euro, 2002, W203. 345 000km

Son's one: GLK class 220CDI, 2009, W204

Sold E class 260E, W124, 1988 beloved car sold after 489 000 kilometres of reliable services (engine M103, clutch and 5 speed manual gear box all original).

E-class, W210 320CDI, 2000[/B], 225 000km, Sold

I started with a half turn in, backed it out until the vacuum problem started, then in just a hair.

__________________
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

thanks ctaylor738.

I assume you did it with the throttle body fully mounted on the engine.

I would like to do it separatly that is why i believe there there is another way ( bosch does it)

Here is the picture mentionend in previous post.
Shoudlm the flap be under the smaller hole on the left, and at what distance?

Attached Thumbnails

 

__________________
Keep us posted especially if your problem is solved
Present cars:
My car: E-class 420CDI, 2008, W211, V8, 180 000km

Wife's one: C-class 220CDI Sport Coupé, Euro, 2002, W203. 345 000km

Son's one: GLK class 220CDI, 2009, W204

Sold E class 260E, W124, 1988 beloved car sold after 489 000 kilometres of reliable services (engine M103, clutch and 5 speed manual gear box all original).

E-class, W210 320CDI, 2000[/B], 225 000km, Sold

The M110 that I was working on is is a completely different design. I don't know where the adjustment is on yours.

__________________
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

My engine is a M103
The adjustment is made with the screw visible on the first picture.

__________________
Keep us posted especially if your problem is solved
Present cars:
My car: E-class 420CDI, 2008, W211, V8, 180 000km

Wife's one: C-class 220CDI Sport Coupé, Euro, 2002, W203. 345 000km

Son's one: GLK class 220CDI, 2009, W204

Sold E class 260E, W124, 1988 beloved car sold after 489 000 kilometres of reliable services (engine M103, clutch and 5 speed manual gear box all original).

E-class, W210 320CDI, 2000[/B], 225 000km, Sold