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#1
03-02-2008, 05:08 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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____________________ Jeff '77 350SL, Euro-Manual 
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#2
03-02-2008, 08:41 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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'70 111 280SE/c 3.5 (4 spd manual) - sold '63 MGB '73 MGBGT V8
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#3
03-02-2008, 09:07 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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ASE Master Tech Quality Enterprises Mercedes Svc. & Restoration Sheridan, IN 317.769.3536
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#4
03-02-2008, 09:11 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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ASE Master Tech Quality Enterprises Mercedes Svc. & Restoration Sheridan, IN 317.769.3536
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#5
03-02-2008, 10:57 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
03-03-2008, 03:43 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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____________________ Jeff '77 350SL, Euro-Manual
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#7
03-15-2008, 11:45 PM
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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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____________________ Jeff '77 350SL, Euro-Manual
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#8
03-16-2008, 12:13 PM
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yes, and it's inexpensive. -CTH
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#10
03-16-2008, 04:53 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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Ron 2015 Porsche Cayman - Elizabeth 2011 Porsche Cayman - Bond,James Bond Sadly MERCEDESLESS - ALways LOOKING ! 99 E320 THE Queen Mary - SOLD 62 220b - Dolly - Finally my Finny! Sadly SOLD 72 450SL, Pearl-SOLD  16 F350 6.7 Diesel -THOR 19 BMW X5 - Heaven on Wheels 14 38HP John Deere 3038E Tractor -Mean Green 84 300SD, Benjamin -SOLD 71 220 - W115-Libby ( my first love) -SOLD 73 280 - W114 "Organspende" Rest in Peace 81 380 SL - Rest in Peace
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Do you know what this part is called?
Linear Mode
