Rough Idle When Cold

[veg_burner]

Rough/low idle when first started in the morning, conks out sometimes if I don't give it a little pedal. After that first start no problem, runs great. (Don't want to be adjusting my idle speed for that reason).
Tried searching the archives but there's so much stuff comes up with 'idle'...
I remember reading something about a vacuum controlled idle valve - or am I dreaming?

[mespe]

but I've attributed mine to high mileage,,, 344K miles is high, isn't it.

After she warms up, she purrs like a diesel is supposed to purr.

[whunter]

Originally Posted by veg_burner

Rough/low idle when first started in the morning, conks out sometimes if I don't give it a little pedal. After that first start no problem, runs great. (Don't want to be adjusting my idle speed for that reason).
Tried searching the archives but there's so much stuff comes up with 'idle'...
I remember reading something about a vacuum controlled idle valve - or am I dreaming?

Test your glow plugs Glow Plug Testing?

If you are running veggie, your mix may be jelling just a little.

Could also be rack dampener needs adjustment or replacing.

[veg_burner]

what is the rack dampener?
wouldn't be the glowplugs would it as it starts up just fine then idles low/rough.
no veggie yet...

[Jimmy Joe]

Mine started idleing rough.
Found a dead glow plug...

[w123jones]

Same issue with me. My glow plugs checked OK. I'm due for a valve adjustment. That may help, but I would think that would also influence starting, not just cold idle.

K.C.
84 300D, 214k

[shadetreetech]

my 81 TDT, idles so rough the whole car shimmys side to side even when warm.I just got it running though after 3 years of sitting.

[DieselAddict]

This has been an ongoing problem for me ever since I puchased my cars and it has come and gone. On one of my cars it got worse after I rebuilt my injectors even though I'm certain the injectors now spray a lot better (one of the old ones had a really terrible spray pattern). If your glow plugs work and you're letting them glow for 20 seconds or so before a cold start, your timing is correct, your injectors spray properly and you've done your valves (if applicable), and you still have a cold rough idle (which is my case) I've come to the conclusion that the only thing that will help is a new relay with afterglow. That's what I'm gonna try on the 87 and 82. I already have it on my 83 and the cold starting is beautiful, totally smooth and no smoke. The newer cars have afterglow from the factory and there must be a reason for it.

[veg_burner]

Originally Posted by DieselAddict

I've come to the conclusion that the only thing that will help is a new relay with afterglow. That's what I'm gonna try on the 87 and 82. I already have it on my 83 and the cold starting is beautiful, totally smooth and no smoke.

where did you get the relay from?

[DieselAddict]

You can get it just about anywhere, any place that sells new parts. Strangely, it's cheaper to buy the "relay kit" that comes with 4 glow plugs than to buy the relay alone.

[shadetreetech]

after inspecting the hard fuel lines under my car I found one to be partialy squished im thinking about cutting that section and patching in some soft line ,hope it helps.

[Shellnekov]

I agree with the relay idea, mine was exactly the same ,got the new relay and 5 plugs for 99$ and never stalls now. Worth a try.Never did install the plugs as mine were good.

[TonyFromWestOz]

Originally Posted by shadetreetech

after inspecting the hard fuel lines under my car I found one to be partialy squished im thinking about cutting that section and patching in some soft line ,hope it helps.

This would be more likely to affect high load operation than idle.
More fuel flow at high load, lowest flow at idle.

[DieselAddict]

I haven't bought the afterglow relays for my 2 other cars yet, but I tried something else. I replaced about 20% of my oil with the Lucas Oil Stabilizer and my cold idle is smooth now! I'm impressed. I guess this fluid does indeed reduce friction (as it claims) which especially makes a difference on a cold start. To have a smooth cold idle, you need good combustion and/or low engine friction. The afterglow relay improves cold combustion and this Lucas fluid clearly lowers the friction. I've also been using the Lucas PS fluid in my 87 300D and it has nearly eliminated a significant leak that I used to have.

[veg_burner]

I'd be wary of the Lucas oil product....
there was a thread I read recently that showed pics of a study someone did, and that the lucas product makes the oil "frothy" and therefore lighter, but that this isn't really a good thing for lubrication. I don't have it bookmarked but you might want to search for 'lucas' and see if it comes up. Just FYI...
Maybe use synthetic instead?
BTW I couldn't find the afterglow relay at the place you mentioned. Do you have a part # by chance?