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  #1  
Old 03-02-2008, 06:08 PM
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1977 350 sl - Engine races out of control

I have a 1977 350 sl that has been running fine for over a year and all of a sudden the engine races out of control as if I'm holding the accelerator to the floor. It happens immediately after starting the engine, cold or hot. It has a 116984 engine (euro) with a manual transmission; a little different than the 450 sl but I have found that most everything is the same. Any body have any ideas as to why this might be happening?

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  #2  
Old 03-02-2008, 09:41 PM
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Check whether throttle cable or bar is stuck. I don't know much about SLs, but that happened to my old 114 250C. Throttle bar was rusted in the hinges and a bit dented so would not rotate back sometimes and engine started racing on startup after pressing (and releasing) gas pedal.

Good luck,

Bert
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  #3  
Old 03-02-2008, 10:07 PM
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* Is the gas pedal stuck on the floor, wedged under several layers of mats? I know, that was a stupid question, but I've seen it happen, and no one bothered to check the pedal first.
* The binding throttle linkage is probably your best bet. There is a throttle rod that goes from the center/left side of the top/back of the motor back to the firewall. It's mounted, spring-loaded, in two spherical pivots. The plastic spherical pivots like to disintegrate.
* If it's not binding linkage, then it's a huge vacuum leak.
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Old 03-02-2008, 10:11 PM
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* Correction to that last post. A huge vacuum leak wouldn't allow the engine to run in the first place. It would have to be something like a hose off at the idle air bypass.
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  #5  
Old 03-02-2008, 11:57 PM
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There's a spring to hold the throttle plate back. Sounds like it got disconnected.

Remember, the big metal plate you see at the top of intake is NOT the throttle. Follow the curve of the metal from that point down and it will lead you to the right place.

-CTH
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  #6  
Old 03-03-2008, 04:43 PM
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Nothing obstructing the pedal area and the spring (throttle) is in tact and working. I am wondering if it might be the Auxiliary Air Valve? But I cant find mine. It's a K-jetronic system and I don't have literature for the car. If anyone out there has a vacuum diagram for this car I would appricate a link to it or a post with pictures.
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  #7  
Old 03-16-2008, 12:45 AM
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problem found...

The throttle plate was being held open by the plastic (Baffle - I don't know what this part is called) that fits between the throttle body and the air intake area. The sides had weakened and I guess it got sucked down; but regardless, I fished the part out and the engine purrs once again. So now trhe question is do I really need to replace this part (baffle)?
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Old 03-16-2008, 01:13 PM
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yes, and it's inexpensive. -CTH
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  #9  
Old 03-16-2008, 03:42 PM
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Question Do you know what this part is called?

What is this part called and where can I get one?
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  #10  
Old 03-16-2008, 05:53 PM
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I have an intake off an 81 350, I wonder if its similar, I will take a look, can you post a picture?

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