1999 E300 – Rough Running
 

Today at noon I started my 1999 E300. At first is run OK, but then after one or two minutes it would seem to ‘miss’ from time to time. I pushed the pedal down and varied the RPM’s and it ran the same. My wife drove it home and I asked if she had problems. She said that she was not notice anything.

My first guess was fuel filters. Tonight I change both fuel filters and ALL related o-rings/seals for both filters. I started it back up and it runs just like it did at noon…it ran great at first, but then after a minute or two it would ‘miss’ from time to time and at any throttle position.

Any ideas?

When my shutoff valve oring went bad (VERY minor staining over a week period of time) recently mine did that at idle, but not higher rpm's.

Know you've got viton orings (thanks for posting that data by the way), how long since that one has been changed? Assume everything is clean enough you are confident there are no other leaks.

Also, do you know the size of the fuel line orings (x4) that plug into the filter housing? They ae larger than the typical oring. How about the pre-filter oring size?

from your previous posts.... it sounds like Emily is one bad girl.....

Any chance you can try a code reader, and see if anything shows up there?

I'm pretty new at diesels, but... (I'm ase certified, and have a few hours around cars)

There is an 02 sensor or something like it on these cars. It sounds to me when it goes 'closed loop' (if there is such a thing for diesels) that the mixture is off.

MAF?
silly as it sounds... air cleaner?
time to go for a good highway run and blow it out?.
fuel? (siphon what is there, and replace it with fresh)
Maybe it's time for a diesel purge?

Anyways... My dime's worth.

For what it's worth... I've had my MY99 E300 for a year. 24K miles. Oil changes, filters, and glow plugs. 72K and counting....

Jnc...

99 E300
99 Boxster
03 S type.
70 914/6.

Can there be codes without the CHECK ENGINE LIGHT?

I November of 2005 all the fuel lines with the o-ring were replaced.

I was thinking of trying a diesel purge. If that does not take care of it I will likely go to the dealership and then sell this POS. For me the negatives of this car far outway and positives. With this car I am always waitng for the 'other shoe to drop' and I am tired of it. No more post W124, W126, or W201 Mercedes for me.

Is there any sign of leakage around the delivery valve seals on top of the injector pump?

What you are describing is almost always a fuel problem...a leak somewhere...can you look to see if there are any air bubbles in the lines while someone else revs it?

I'd replace that shutoff o-ring...even if it was done in 11/05 it could be leaking again. Mine did after less than 2 years, just after they started selling ULSD here.

There are pending codes, which are not codes per say, but.... diagnostic cycles that are not complete. I'm thinking there are like 8 diagostic cycles.

The typical $80 tester will tell you the code if you have a check engine light, and the systems that are still 'pending'.

Generally speaking, pending codes will also cause you to fail an emmisions test. (well, PA doesn't test diesels) They are sort of like a yellow light, prior to the red light.

A good read of a OBDCII tester manual will provide you with lots of insight. I consider an hour read of the manual, much better than just handing a dealer a $100 bill for a diagnostic check.

I think the hardest part of the new diesels is many things are 'out of our hands'. It's a little like cars when the points ignitions turned to solid state, and carburetors turned into FI. Everything we knew, became new again.

I'm very happy with my W210. But, I've also never had an earlier Merc. From my VW days, I can tell you that the 12 volt cars were always better than the 6 volt cars, and dual port was better than single port, but when they added a water pump, I just lost interest. It sounds like maybe the same for you. As the electronics got added, your interest went elsewere....

good luck....

Mine lasted 2 1/2 years and got replaced with viton this time. Will be interesting to see how long IT lasts.
*******

The O2 and MAF should both set off a CEL if not operating properly. In my experience you don't need a CEL to know the MAF is bad; the lack of a turbo and any meaningful acceleration tells you before the light lites up.

A DP might help but if it did, I would be left wondering what caused the problem that the DP cleaned up!

Weak spring on the EGR valve?

I have had the shut-off o-ring leak before. I caused hards starts and then ran fine once started. Also, you could smell fuel outside of the car and inside. I have none of these symtoms.

Did you ever replace your K40 relay or the MAF? If there are no fuel leaks (check under the black plastic cover too), I'd suspect those two. But if there are any pinging noises while the engine is missing, it's probably the injectors.

The MAF was replace at about 58,000 miles which was about July of 2005. I do have a spare K40 relay that I bought new, but did not need at the time.
There is no 'ping' when it misses.

What does the K40 relay control?

Yesterday was the first that I had noticed it. Monday I filled up at a different place than where I currently buy fuel, however, it is the same place where I used to buy fuel.

The K40 provides power to the shutoff valve among other things. Unless it has died suddendly while driving I doubt it is the problem.

I wouldn't rule out bad fuel as being the culpret...I'd drive it through this tank and see if it still has a problem on a fresh tank from a different source.

In that case I suspect bad fuel or a fuel leak somewhere as I mentioned last time. Did you check under the black plastic cover? See if there's fuel puddling in one of the injector holes. Also try adding some cetane booster and water disperser if you suspect your fuel is bad.

As far as water I remember when GM had their junk diesels there was a sensor to detect water in the fuel. With all of the monitoring on a 606 is there not a sensor to chek for water in the fuel?