1991 300d 2.5 idle 124 - PeachParts Mercedes-Benz Forum

xeus · #1 02-09-2008, 09:46 AM

I have the above vehicle,I've read many threads on the older diesels where the fuel rack dampner bolt can be adjusted or replaced,but what about the 602's.How can a rough idle be adjusted without just raising it via the linkage?

pmckechnie · #2 02-09-2008, 10:17 AM

I don't believe the 902 has a rack dampner bolt. I am usually wrong but maybe I will ge lucky this time.

bobodaclown · #3 02-09-2008, 01:43 PM

Idle speed is electronically controlled and no adjustment is necessary. If problem exists, check by-pass air valve operation.

2.5Turbo · #4 02-09-2008, 03:17 PM

A rough idle could be a number of things. Injectors, air in fuel, bad filters, intake problems, etc.

If you're talking about a low idle, then make sure the ELR actuator (I think that's what it's called) on the IP is plugged in and functioning. Without it, the car will idle somewhere near 500rpm and will not compensate for loads like A/C.

sixto · #5 02-09-2008, 06:25 PM

Quote:

Originally Posted by bobodaclown

If problem exists, check by-pass air valve operation.

Does the 602 have one of these? AFAIK there is no air throttle in a 602.

Sixto
87 300D

sixto · #6 02-09-2008, 06:25 PM

Have you checked the engine mounts?

Sixto
87 300D

xeus · #7 02-09-2008, 06:48 PM

the idle is low around 600 rpm.did a diesel purge and rebuilt the injectors.

babymog · #8 02-09-2008, 06:55 PM

The idle control is not working, is the tach and A/C compressor also out? Would then be the overcurrent protection relay or fuse behind the battery.

Idle is electronically controlled, resister pack looks like a knob near the fusebox, if the air-flow sensor or ?? are not working properly it will idle low.

xeus · #9 02-09-2008, 09:00 PM

Ok just checked the fuse behind the batt,its fine and the tachometer and a/c are also working.

sixto · #10 02-09-2008, 09:04 PM

Someone has a similar problem with a W140. Dealer suspects it needs a new engine wiring harness.

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

Sixto
87 300D

2.5Turbo · #11 02-09-2008, 11:13 PM

Quote:

Originally Posted by sixto

Does the 602 have one of these? AFAIK there is no air throttle in a 602.

Sixto
87 300D

There's a little butterfly flap valve between the turbo and the EGR. If that gets stuck closed it makes the engine cough and sputter while puking white unburned fuel smoke when revved. It really doesn't affect idle too much at all...at least as far as I could tell when I got curious and pushed it closed while idling once