Greetings Forum Members,

I would like to report to all those chasing a high idle issue with your Djet fuel injection systems
what I discovered to be my biggest problem but never found mentioned to check in all my researching.
And that is to MAKE SURE THAT YOUR THROTTLE BODY FLAP IS CLOSED COMPLETELY AT IDLE AND OFF THROTTLE.
After testing sensors, checking engine vacuum, checking and adjusting timing, adjusting the MAP sensor,
adjusting the throttle position sensor, rebuilding the idle control valve and doing a smoke test for leaks (***not finding any ) I still could not
adjust the idle to spec with the idle screw. Finally, tonight, when checking the switchover valve function
I found that I had no vacuum in the line coming from the throttle body. I blew into the line . It was not blocked. The line gets vacuum from the opening in the throttle body below the flap. If the flap is not completely closed at idle or off throttle then there is no vacuum to the line = VACUUM LEAK. I removed the air filter housing and sure enough the flap was just so slightly not completely closed. I remove the throttle body. loosened the bolt holding
the throttle body flap shaft, loosened the throttle position sensor nuts and tightened the throttle body flap shaft nut while holding the flap tightly closed. I readjusted the throttle position sensor, installed it, the air cleaner and vacuum line. I started the engine. Smooth adjustable idle on the 1973 450sl.
I had been dealing with this problem for over a year. Prior to resolving this issue I could not get my idle below 1000 rpm without playing with the MAP and or retarding timing which resulted in less than desirable engine performance.
(***Actually when I did the smoke test, smoke did rise from the throttle body but I assumed that that had nothing to do with my vacuum leak. I was looking for leaks from lines and hoses, NOT THE THROTTLE BODY.)

I Hope This Experience Can Be Of Help,

Knarf

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72 350SL #69
73 450SL Parts Car?
78 450sl Parts Car
79 450SLC - Sold
1985 280sl
87 190E 2.6 - Donated
90 300E-Junked
97 E420