240D shakey at idle, fast idle, how to adjust?? - PeachParts Mercedes-Benz Forum

unkl300d · #1 10-17-2003, 04:14 AM

Hello, the 1979 240D has a bit of a fast idle especially after long rides.
The engine shakes at idle more when the car has been warmed up than when idling at first start up in morning.

Very shakey, that is , it shakes the car and driver but the idle is constant and does not fluctuate. I believe that the rate of idle is too fast.

When I bought the car, the idle adjust dash knob worked but now it does not seem to make a difference when moved from clockwise to counter clockwise direction.
So this cable may be undone or mis-adjusted.
The motor mounts are brand new and so are the front shocks.
It has one new injector (closest to firewall) and the other three
have undergone two bottles of diesel purge but not physical cleaning.
The motor runs fine, sounds great and the power is good for a 240D automatic trans {133K miles}. It passed the PPI but the rough idle was noted.
My other mechanic said the engine sounded fine and did not recommend changing the injectors but said the injector pump may need timing, i.e. remove pump and time etc. ($$) He however said that I should just live with it as is.

After reading the archives, I understand that the rack damper screw can be adjusted or replaced.
>>>Does the 240D have one??
>>>>How do you adjust the idle on the 240D?

The car does not smoke oddly and it does not nail at all. The valves were adjusted by an indie a few months ago as per records. I don't believe the timing chain is in need of replacement becuase the mechanics did not site this
and there is no audible jangle sound as far as real layman diagnosis goes.
Thanks for your help.

Denis

Rick Miley · #2 10-17-2003, 10:44 AM

As far as I know, the 240D does not have the governor idle screw. If your dash mounted idle adjustment is not working, then what you should do is open the hood and watch the stop lever while you reach in and turn the knob on the dash. If the cable attached to the stop lever moves, then you can adjust it at the mounting point on that end. If not, then it has probably come apart at the knob.

Edit: This thread has a picture of the stop lever. Yours should be similar but not exactly the same. Notice the two cables? One goes to the cruise control actuator mounted on the inner fender. The other is the idle adjustment. Both are adjustable at that mount in the lower left corner of the picture.

unkl300d · #3 10-18-2003, 01:29 AM

Thanks Rick, I will check that out.
Denis

wgreen · #4 10-18-2003, 02:12 PM

if you look from the stop lever linkage down, behind the IP, there is a connecting rod. that rod pulls the IP pump arm up against the idle adjustment bolt, the bolt is apox. 2-3" long and has a lock nut at the bottom, turn the bolt CW to increase idle CCW to decrease. at least that is the case on my 1981 240d.....

unkl300d · #5 10-19-2003, 09:39 PM

BILL, BRILLIANT ! I see what you mean.

I will adjust this soon.

Thanks

Denis