1990 Mercedes-Benz 420SEL Q&A
1990 Mercedes-Benz 420SEL Question: HIGH IDLE
My Benz just had a new transmission installed and since then, the idle is way too high. This model has no throttle body or idle throttle sensor. It has an EHA sensor on one side of the carburetor and another unit on the other side (don't know what it is). I was told it was probably the idle air control valve...I replaced it; no change in the problem. Is there something that needs to be reset or is it the EHA sensor,etc. I am tired of leaving my car parked in the garage!! Runs great other than the jerking and peeling out when put into gear. HELP!!! - Visitor
you really need an experienced MB tech to diagnose this for you. buying parts at random is expensive and won't fix the problem. - overbys
Idle control valve (5 inch cylinder with 2 wires on it directly below and at front of the air filter) should have 4 to 4.5volts going to it, if not, pull out carpet on passanger footwell, remove plastic cover (1 10 mm bolt at bottom middle) right on the footwell wall in middle u will see a black box, 3 inches by 4, this is the idle control relay, try changing it, also on a merc 116 engine (1 air intake to air filter) take off air filter, about 8 inches away from idle valve u will see temp sensor, (small round green plug with 2 wires on top, u want the one with a black stripe on it, join into that wire ONLY and then connect to vehicle ground, (if that ground was bad changing either idle relay or valve will not work. Make sure it is that temp sensor u ground and not the one on the thermostat housing - jaguarxj6
It is not uncommon for the idle air compensator to get stuck in one position, resulting in the engine idle speed (rpm) being too high or too low. Replacement of the failed compensator may be nece...
when driveing it idle well when stoping and putting in park it idle high
my 420sel idle high when in park but not when driving why