I have a 78 240D manual.

It does not shut off when turned off, I have to stall it out or push the red stop button under the hood. That is annoying, but I think I can live with it.

But this morning on the way into work, I went to shift and the throttle continued to rev at the same level after I pushed the clutch in. the revs didn't come back down. It continued like this until I parked the car.

It isn't a terrible problem because once I shift, the transmission brings the throttle back down to normal revs and it drives normally.

Also, it doesn't open up by itself, just stays where I last pushed it to.

What is this? Vacuum pump? Is it likely to get worse? I plan on driving this 1900 miles tomorrow to Oklahoma and back to Michigan.

Thanks for the help.

__________________
81 300D 250K (sold)
79 240D 200k
83 Volvo Station Wagon (282k)

JoshMB,

Those cars have a manual idle control knob on the left side of the steering wheel, on the dash, which looks a little like a black plastic, squashed jelly bean or something. You turn it one way to speed the idle up and the other way to slow it down. It is used to make the car idle ok when it is cold. When the engine heats up the engine can race a little when you have it in neutral. Turn the knobin the "slower" idle speed direction to slow it down. I do not remember which way is which but the response is apparent.

Also, check to see if the linkage in the throttle actuator area is clean and lubed. It can get pretty sticky after 25 years if no one cleans and lubes the ball joints in the linkages. This is something I routinely combine with a valve adjustment as you have to disassemble the whole mess to get the valve cover off.

I have made some "custom crafted" parts from popsicle sticks to take up the slack in some of the linkage parts on my 240D (mainly because I cannot get the dealer's microfiche files to agree with the parts in my 1982 240D) and these have been known to change shape after being wetted with Diesel fuel, leading to issues with throttle response (nothing a new stack of popsicle sticks can't fix though). I do not recommend such solutions, but I know if I did it others might also, so look for home made junk in there too.

Good luck and I hope this helps. Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

On my 240D there is a spring connected to the rear IP mounting bracket on the inside/bottom of the IP, which hooks to the throttle linkage. It's a real bear to get to; you'll need a flashlight to see it, but if its broke or is missing it will not allow the throttle to return to the idle position.

Good luck.

__________________
1976 240D
1987 560SL
2007 E320 Bluetec
1998 C280 (now son’s car)
1982 240D Manual - Sold

Thanks for the quick responses.

The pedal does return to it's regular position when I take my foot off the accelerator.

I have not had a chance to go under the hood and lubricate anything. TO be honest I feared a vacuum problem (which I know the car has in general) and overlooked a such a simple solution.

The black idle knob is working fine, although it is loose in the dash.

Frankly Speaking, what is the IP? I don't understand the Abbreviation. Is that under the hood or under the pedal?

Thanks.
Josh

__________________
81 300D 250K (sold)
79 240D 200k
83 Volvo Station Wagon (282k)

IP = injection pump.

A vacuum problem will cause the shutoff to fail, requiring that you use the lever under the hood. Usually cheap and easy to fix, being a broken line or leakking fitting.

Check your throttle linkage -- do you have cruise control? If so, check that for binding, too.

If it isn't the return spring or linkage, it sounds as if you might have a sticking governor, a true weirdo for these cars (never heard of it before, in fact). Bad governor diaphram on the older vacuum governors is fairly common and a BIG PROBLEM!!!! Carry a 17mm wrench with you until you get this fixed -- if the governor really goes splaa the engine will run a full throttle and blow a rod or four. You will have to loosen the injector cap nuts to kill it, the stop lever won't work, nor will the mechanical shutoff on the W115s. You will get a bath in diesel fuel, but the engine won't explode!

If you can't find anything binding in the throttle linkage, or any broken parts, I'd take it to a good MB mechanic to be on the safe side.

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!

Josh,

IP = injection pump

The knob on the dash is tightened by the little chrome ring, but it is hard to tighten it effectively.

Throttle position is controlled by your foot through the linkage, unless you have cruise control and it is on. Some cars have a vacuum controlled cruise control sytem, so if vacuum is not working correctly the likelihood would be for the cruise control not to work at all.

So, if the linkage is hanging up, it is probably just getting sticky from corrosion and crud. Good luck, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

In a runaway diesel or any engine the fastest way to kill it in an emergency will be to stop the air. If a bad governor caused a runaway use a large towel, plastic bag, wad of paper or your hands to close off the air intake. Engine will slow and die within seconds without air.

I just had this problem with my car. It turned out to be a faulty shut off valve that wouldn't hold a vacuum. Its relatively easy to check the valve once you can pull it out. Essentially, push down the piston, put a finger to seal the opening on the shut off valve, if it holds you have a leaky line. If not, it's obviously the valve.


Good Luck