I have a 99 E300 and when i start from cold is runs ok for about 30 secs and then begins to run rough which then lasts until it warms up. Once warm it then runs great. It has 156K on it and I recently bought the car so unsure of history. When the misfire happens it smokes too... so was thinking too much fuel. Could this be injector problems? Any ideas?

I would start with checking the GP's and relay with a multimeter. The relay may be cutting afterglow out too soon.

Go to dieselgiant.com and follow the tutorial for the W123 thereon. Relay is diff, principals are the same.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

I agree with Terry in that the gp's are supposed to stay on for 1-2 minutes and if you are experiencing problems after 30 seconds it might indicate an issue with the relay. My only caution is that if you have a cylinder which misfires when cold after 30 seconds of running on GPs it might still indicate an underlying problem like a weak GP, low compression or a bad injector because the afterglow really doesn't prevent misfires - it aids in more complete combustion for emissions but the engine ought to run on all 6 cylinders after the initial GP cycle. Typically the most noticeable effect of the end of the afterglow cycle is some increased clatter until the engine warms completely, but no roughness.

You might consider running a can of diesel purge through it. If you don't know its history you don't even know what kind of fuel the PO ran in it...for all you know there is some chicken fat in there clogging up the works.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

I'd say you have a bad GP or 2. I had the same problem. After you start the car, does the orange GP indicator stay on? If so, that idicates a bad glow plug.

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Mike Mass
Freehold, NJ

1999 E300 TD 178,000 miles
2007 E320 Bluetec - Sold

1998 E300 TD - R.I.P.

Ditto.
If it was an not working afterglow issue I would think that the whole Engine would run ruff. Unless in the OP by miss you ment the whole Engine was miss firing.
Check the Glow Plugs and the Relay to.

Next choice would be an Injector issue. While it is missing loosen and tighten each Injector Hard Line Nut. When you do this to the good one there should be an obvious change to the worse as to how the Engine runs. When you get to the bad one there will no or a little differance in how the Engine runs.
However, the above only identifiys the problem Cylinder.
You will have to swap Injectors and see if the problem follows the thought to be bad Injector to the new location.

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84 300D, 82 Volvo 244Gl Diesel

He's def got a bad GP. The after glow is not working, which could be a relay issue. But my guess and the more likely cause is that he is probably firing up on only 5 good GP's. If it is warm enough outside, he'll have no prob firing up on 5, but the afterglow stays on for....? I'm not sure. is it an extra minute? 3 minutes? Whatever it is, that is a sure symptom of the misfire in the one cylinder.
Grayslinky, give us the details of where you are. i.e cold morning starts, you in green bay, WI, or sunny south CA, etc? Also, if it is what I'm predicting, I bet that thing belches white smoke out the exhaust till you are warmed up. That is the unburnt fuel passing thru the cylinder with the bad GP. Is that the case? I went through the same exact thing. Replaced the bad GP and all good.

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Mike Mass
Freehold, NJ

1999 E300 TD 178,000 miles
2007 E320 Bluetec - Sold

1998 E300 TD - R.I.P.

Mine is doing the samething. I dont think it's a GP cus it will miss around 1200rpm once it's warm. I think it's either the IP or a bad injector. Also white smokes bad untill it warms up. My DV seals are leaking slightly could that cause a miss? Thanks

Frothy fuel can cause a bad spray pattern/miss. Replace the DV orings and seals; then check the spray pattern of the Injs if that doesnt clear it up and compression after that if the problem persists.

Ask for help if you havent done DV seals before.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)