1993 300D 2.5 TD rough idle
 

My 300D starts without hesitation then, after idling for a minute or two it starts to run very rough. It clunks and smokes until I start driving then it's fine. Sometimes it will run smooth from the start but seems to have less power as if the turbo is not working. I don't know if these two problems are related. Any thoughts are welcomed. Thanks

Check your glowplugs. The glowplugs pre-heat the chamber and if one is bad, it will exhibit the symptons you are describing.

My 91 300D is doing the samething. #2 GP is shorted. Glow light doesn't come on until engine starts. it will stay on for 2-3 minutes after engine is started. will 1 bad GP causes that?

Any hint? thanks!

A shorted glow plug will do that!

My car does the same. Rebuilt injectors didn't cure anything. All the glowplugs are good. The engine starts without difficulties at any temperature, with or without the block heater. When not using the block heater, it starts to misfire when the glowplugs are shut off (afterglow time is up to 60 sec. on that engine). When using the block heater, there is almost no misfire.

Two weeks ago, I went to a ski resort : the parking was on top of a hill after a steep climbing of a couple of kilometers. After 8 hours at 15 F (unpluged), the engine went on without any misfire. Don't know why ! (altitude sensor ? decarbonizied prechambers after the steep ascent ?). The next morning, parked down the hill, the misfires were back.

I'm planning to have a compression check (not without some apprehension !). I'll keep you informed.

Thanks! CJ Is yours having that symptom in the morning?

DR,
Since injectors has nothing to do with it...could it be the valve stem seals leak overnight? My 83 SD never has valve stem seals changed and it doesn't do that. ???

I'm planning to do the GP this weekend. Ordered stem seals and gasket from Phil yesterday for next step.

SVose,
 

What color is the smoke?

I had a problem like that before and it was a bad GP. the extra smoke was unburnt fuel.

BJ

I don't think it is valve stem seals. The smoke is unburnt fuel.


CJ

Could a marginal glow plug be responsable for that ? As I said, as long as the glow plugs are on (and they stay on for a minute after engine start), the engine runs perfectly.

Amarginal Gp could do that, check them at the relay box for resistance.

DR,
I agree the smoke is unburnt fuel. thanks!

got new GPs and gaskets today. Hopefully that problem will be cured. I looked under the hood today and wondered what size HEX screws are on the intake manifold. Is it a 6 mm? should the manifold come out first before the crossover tube?

Please advice. thanks!

Don't know about the exact size of manifold screws, but if you remove the manifold, the crossover tube must go out first. It's attached to each end (the bolt on the turbo end is located under the tube) : remove the bolts and lift it first at the manifold end then pull it out from the turbo end. The shop manual says to renew the gaskets at each end.

It may be unnecessary to remove the intake manifold to change GP but it certainly will make the job easier. I didn't found any description of the GP removal procedure on the CD but I've seen many posts on the subject on this forum.

I've seen several pictures of engine bays on these diesels in which the crossover tube obviously did not match the rest of the engine. That is, in terms of condition and color. In one case they said the crossover came from a junkyard.

So, I think what this could mean is that the cast aluminum parts are more delicate than what some people might be used to. I plan to be careful if my crossover & intake ever have to come off, with a few treatments of penetrating oil beforehand. Too much torque on the bolts and something might break.

Ken300D

(Well, I think its cast aluminum - might be called something else.)

You can access all the GP's without removing the intake, you just have to take your time and wiggle your hand under there. The bolt size is eaither a 6 or 6.5 mm. If you want to remove the intake manifold, you will need to remove the fule lines first, then all the stuff that is bolted to the intake. make sure you lable the lines, they look very similar in lenth.

Good luck.
I am actaully removing my intake next week, since it is weeping slightly and I am very anal about having any seepage on my spotless engine. :)

GP's SHAPE is matter
 

thanks guy! bolts on Intake manifold are 6mm.

I managed to change all the GPs on my 91 300D with the new ones(cone shape from middle to the end. the old one has the same size all the way to the rounded end). Fired it up and it smoked like crazy. they sure make cold start a lot quicker but the smoke(light grey) never go away even the engine reaches the operating temperature. It also has pretty rought idle and misses. So I ended up putting 4 of the old ones back except the one which is shorted and it runs a lot better with very little smoke. I'm sure if I get another GP like the old one it will smooth out. I read it from another thread someone mentioned something like that and I had proved it. For those of you who is planning to change GPs be aware of this issue.

Here are some steps to make the job easier. You don't really have to remove the Intake manifold(IM) unless you want to clean it up like in my case.

1. Remove those 3 (2 on IM and one on Turbo end) screws on the crossover pipe, push it down on the turbo side this will separate it a little from the IM. Tilt it back toward the end of the engine and pull it up on the turbo end. cover both opennings before you proceed to next step.(not fun to do some fishing later)

2. Remove the throttle control machanism and the CC unit from the IM.

3. remove the connector for the pressure sensor and the vacuum line to cut off switch

4 remove all injector lines.

5. GPs


Be careful with those plastic wire hangers and injector line retainers. they break very easily. have a couple of them in hand will be a good idea.:confused: