1989 420SEL High Idle and easily overheat - Mercedes-Benz Forum

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post #1 of 2 (permalink) Old 11-25-2009, 11:07 PM Thread Starter
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Smile 1989 420SEL High Idle and easily overheat

just got this 420SEL.

the engine idles very very high rpm when the car starts then goes easily overheated at over 100 degrees within 3 min.
i can even drive the car at 45 mph without a foot on gas pedal. it just keeps on going until i brakes.

last night i was at Mcdonals drive thru waiting for the car in front for about 3 min, the car overheated and smog came out and had to get out of the drive thru abandoning my food and had to kept driving to cool down the engine, then the smogs gone and rpm returns to normal and temperature went back to normal.

this high idling is only happens when the car is in parking mode and revs up crazy like someone is stepping on the gas pedal constantly, but when the car drives out on the roads, the temperature backs down to low and rides so smooth and cool.

is there any way i can adjust or lower the engine idling myself?

time to time the idle resumes low when i put my foot on the brake pedal hard and put the gear into drive.
its very quiet and smooth car when driving..

Last edited by irvineharley; 11-27-2009 at 05:21 PM.
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post #2 of 2 (permalink) Old 11-27-2009, 10:20 AM
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I would first check your throttle body and idle air controller motor. If they are dirty, give them a good cleaning.

Also, check for vacuum leaks, it sounds like you may have a big one.

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