1984 500sl High Idle Issue any one have a 500sl m117.963 vacuum diagram

[Georgevlado87]

High idle hell im not on often and not good at this forum thks for the help btw its a 500sl m117.963

[Diseasel300]

I'd start with the idle control solenoid. Sticks right out front above the coolant hose. Pull the plug off and see if you have 12V. If you do, cycle the plug a few times, you should feel the solenoid "vibrating".

If no 12V and no "vibration", there is a control box behind the glovebox that controls the idle speed. If it fails (usually cracked solder joints), the default is to run high idle (1500-2000 RPM).

[Georgevlado87]

Ya i dont have a volt meter but the idle went higher when i disconnected them

[Georgevlado87]

Originally Posted by Diseasel300

I'd start with the idle control solenoid. Sticks right out front above the coolant hose. Pull the plug off and see if you have 12V. If you do, cycle the plug a few times, you should feel the solenoid "vibrating".

If no 12V and no "vibration", there is a control box behind the glovebox that controls the idle speed. If it fails (usually cracked solder joints), the default is to run high idle (1500-2000 RPM).

Thks for the input

[Diseasel300]

Mine gave me intermittent problems for years. It sometimes was normalish, sometimes up around 1000 RPM, sometimes 1500, occasionally 2000. The latter two were scary, driving in traffic was a clenching experience!

For the longest time, I suspected vacuum leaks since pulling the plug off the idle solenoid always made the idle go higher. When I pulled the idle control box, it was obvious that cracked solder was the culprit. Resoldered 4 years ago and it hasn't given me a single problem since. Cold idle is up ~1000 RPM, then drops to ~600 RPM relatively quickly.