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Old 04-14-2003, 12:37 AM
Registered User
Join Date: Apr 2003
Posts: 13
Angry idle probs, loss of power, valves?

Hello friends, how is everyone. Ive owned a 78 240D for 1.5 months. Was running great.
not any more. Lost a little power and if that wasnt enough.
when I stop at a light.....the idle is rough.
enough of my poetry though. I'm thinking the valves need to be adjusted. Ive got the
feeler gauges. I understand that there are special wrenches. But Ive also heard you don't
need them. If I don't need them I don't want them. Basically I'm looking for any advice
on how to go abuot this. i.e. How tight should the be on they feelers?What should I do?
What shouldn't I do? I greatly appreciate any advice. Thank you very much all my fellow
deisle heads Bennylolo from the frisco Bay via VT peace.

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Old 04-14-2003, 01:12 AM
Mark Tamburrino
Posts: n/a
I adjusted the valves on my 300sd using two open
end 14mm wrenches. The special wrenches would
probably make the job a little easier and I would
get them if I worked on MBs for a living. I think the
78 is similar to my 82, and the Haynes Manual says
the clearence is .1mm on the intake and .3mm for
exhaust, engine cold. The feeler gauge should
slide with a very slight resistance. This is the hard
part, since you must keep the adjusting nut from
turning once it is in the desired spot as you tighten
the locking nut. I don't have a torque spec for
the locking nut but if it is too loose it can turn
back further when the engine is running and reduce
clearence to the point of the valve hitting the piston.
If you apply excessive force you can strip the threads
on the valvestem. I tightened mine pretty hard,
but can't really say to what torque. The job should
not be hurried. If you are just concerned about
how the car runs you can just make sure there
is some clearence on all your valves, if you have
clearence on all valves I don't think that is your
Mark T 82' 300SD 280K
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Old 04-14-2003, 01:55 AM
BIGRED's Avatar
Registered User
Join Date: Mar 2003
Location: Coarsegold Ca
Posts: 693
It could things other than the valves. What makes you think it is valves?

Could be fuel filters, just needing a good ole blowout of engine gunk.

How do you drive it, easy and conservative? jump on it and let the revs get up there? Add any additives to the fuel?

If it were mine and the valves had not been altered since it was running fine, I would first take it for a run and open it up, the kind of opening it up that causes people behind you to wave looking for the lines in the road.

Next I would change the fuel filters.

Good luck
1980 300TD-T (82 Turbo and Trans) 159,000 Miles "Jackie-O"
1983 300SD 272,000 Miles "Aristotle"
1987 Jeep Wagoneer Limited - keeps the MB's off the ice and out of the snow
1994 BMW 530it
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Old 04-14-2003, 11:36 PM
Registered User
Join Date: Apr 2003
Posts: 13
wizork in progresso

hey this is bennylo. replaced the filters and drove it hard. It runs better but its still not right should I turn up the idle. or try some other things first. let me know.
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Old 04-14-2003, 11:40 PM
ned2683's Avatar
Registered User
Join Date: Oct 2001
Posts: 693
trying running a can of diesel purge through it.
198? 300D ???K - Future DD
1989 300TE 285K - traded in '12
1984 300SD 186K - Sold in 08
1978 300SD 330K - Died in 05
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Old 04-15-2003, 07:56 AM
Former Dieselholic
Join Date: Feb 2002
Location: West Michigan
Posts: 380
I have the same symptoms on my 81 300TDT...I adjusted the valves, changed both fuel filters, and ran *6* cans of DP thru it! No change. I now also have a rough idle all the time, worse after a hard run.

Here is my humble suggestion, check the rack dampener, and possibly motor mounts. That is what my next task will be...

Current: '91 300TE 4MATIC 317k and climbing...
'81 300TD Wagon 168K "Tank"
'83 240D 216K 4spd manual "Da Bear" (aka best car ever)

"Never sweat the petty things...
and never pet the sweaty things."
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