what is the correct idle for a w140 300sd 1993?

[mirage1]

i'm idling at 525rpm I think it is low.
getting vibration in the seat replced engine mounts and still vibration
i'm thinking it sould be around 650 rpm?

[Brian Carlton]

650-675 is preferable.

I'm not sure if the W-140 has the dial adjustment for idle speed............

[bobodaclown]

Diesel Engine 610-650
Specification is with electronic idle spped maintaining RPM. Idle speed can be adjusted for customer satisfaction.

[sixto]

No idle trim knob in a W140.

There's a connector to a round device on the back side of the IP. Pull the connector with the engine running. If rpm doesn't drop, EDS isn't communicating with the IP. If rpm drops, I'd rather have bent rods

Is the tach working? If not, check the OVP fuse and relay. I don't remember where they are in a W140 or if a W140 even has them. I hope it's not one of the modules in the breadbox by the right hood hinge because they all look expen$ive. Check also the wire to the flywheel sensor behind the oil filter (quite a chore in a W140).

My guess is the AC compressor won't engage either indicating it's probably a bad OVP relay or flywheel sensor.

Being a 93, it's subject to MB's biodegradable wiring harness.

Sixto
87 300D

[mirage1]

Originally Posted by sixto

No idle trim knob in a W140.

There's a connector to a round device on the back side of the IP. Pull the connector with the engine running. If rpm doesn't drop, EDS isn't communicating with the IP. If rpm drops, I'd rather have bent rods

Is the tach working? If not, check the OVP fuse and relay. I don't remember where they are in a W140 or if a W140 even has them. I hope it's not one of the modules in the breadbox by the right hood hinge because they all look expen$ive. Check also the wire to the flywheel sensor behind the oil filter (quite a chore in a W140).

My guess is the AC compressor won't engage either indicating it's probably a bad OVP relay or flywheel sensor.

Being a 93, it's subject to MB's biodegradable wiring harness.

Sixto
87 300D

It was at the dealer and they said it to start with the harness $475 + 2.5hrs= $800ish

[mirage1]

the dealer is pretty fair with me,allow me to go back and talk directly with the tech(s).
3 opinions said it is the harness, the one senior tech said "the timing seems retarded but first do the harness it is the original one."

[mirage1]

everything works on the car,it was in for oil presr sender and front springs.
mentioned the vibration.
they came up with Harness

[sixto]

If timing is retarded, they can use their snazzy RIV tool to set it for you. They might hit you up for a new chain.

Front springs can't be bad so soon unless you go off-roading. My guess is the fluid filled lower control arm bushings are shot. Cheaper to replace the springs so hope they're right.

Sixto
87 300D

[Bill Ladd]

On older 603 IPs, there is a mechanical idle speed adjustment (Item #3a -- locknut and flat head adjustment knob). Not sure about later model 603 IPs.