1998 E300 smokes going down hill
 

My 98 E300 runs perfectly on flat ground or uphill. It idles perfectly and creates tons of power. As soon as I start down a long hill and give it even the tiniest bit of throttle, it starts belching white smoke and missing. If I get on it harder and put a load on the engine it will stop. If in park, I take the rpm to around 2000 (same as it seems to be going down hill) it will miss and pump out clouds of smoke. I have replaced all the fuel lines plastic and rubber, all the o rings, all the fuel filters including the tank screen, the glow plugs and used diesel purge. The car has 140K miles and I drive it 120 miles per day on the highway. Anyone have any other ideas?

well, since white smoke is usually a sign of water have you lost any coolant in the cooling system?

I'd say maybe there was water in the fuel filter but since you changed it I don't think that's it so I am thinking maybe head gasket.

I've posted about a similar problem in the past with my 85TD. My smoke is not white and as far as I know it only happens in cold weather. It's been happening with mine for a least a couple of years and no good diagnosis yet.

Your smoke is probably different if it is not white. I used to have an old diesel which would do this too - I think it was due to a ring or valve seal problem...does yours consume any oil?

Not enough to speak of.

It doesn't use any water and doesn't use any oil. It has a very strong smell of fuel, like when you are stuck behind a big diesel truck. I see the people behind me backing off to avoid the cloud! Once I hit level ground and I put a load on the engine, it stops.

You've confirmed that at 2k high idle there is no air in the plastic fuel lines?

Every now and then a tiny bubble will go by but no more than that.

What an odd fault. I think its likely fuel related (you have checked for oil/water contamination haven't you), I would be looking at the injectors.

Yeah, I guess that would be my next area too...it would not hurt to have them pop tested.

No problem with water or oil getting where it doesn't belong. The injectors were done a year ago but that was 60K miles. Maybe time to look again.

Is indeed an odd set of symptoms.

I'd continue to monitor water and oil levels and then probably have the inj's tested if you have somone close by who can do it. Maybe an inj is weapy or has a bad spray pattern that only occurs during mid range rpm's and low fuel demand conditions.......?

I'd also like to know how long you have experienced this for? It doesn't take a lot of water to make a cloud of smoke so I would not be so quick to discount the coolant theory though if you said you have had this happen for a long time and not noticed any coolant loss then I would say it is probably not it.

It has been a few months now and I haven't lost any coolant. The smoke has a very strong fuel smell and I am convinced that it's unburnt fuel.

A nozzle not closing sounds feasible.