1987 420 SEL Idling fast at 2200rpm.

[Sandy]

G'day all,
I have a 1987 Mercedes 420 SEL that's suddenly started to Idling fast at
2200rpm as if the automatic Choke was stuck on..
I removed the air-cleaner and sprayed all the linkages and checked that
the solenoid was working correctly.
Has any one had this problem before and can offer any remedies.
I've had this limo since new and it has been very faithful to me.
Hoping someone can assist in keeping the old girl going :)

Regards ..Stephen

[Roland Franzius]

Post by Sandy
G'day all,
I have a 1987 Mercedes 420 SEL that's suddenly started to Idling fast at
2200rpm as if the automatic Choke was stuck on..
I removed the air-cleaner and sprayed all the linkages and checked that
the solenoid was working correctly.
Has any one had this problem before and can offer any remedies.
I've had this limo since new and it has been very faithful to me.
Hoping someone can assist in keeping the old girl going :)

My first guess is the cold start regulator. Its a fuel enrichment
bypass, that is heated electrically and by contact with the engine to
stop after reching a minimal working temperature. It is contolled by the
vacuum in the engine housing. So there a three weak functional spots:
Irs electric heating, its vaccuum membrane between engine housing and
intake manifold and the radial gasket on the crankshaft that guaranties
the engine house vacuum.

But first have a look at schema of the cold idle regulator for your
specific machine. Don't know exactly which injection system was used in 87.