Car did not idle rough until mechanic replaced injector pump seals (the ones going from the pump to each injector). I noticed as soon as I pulled out of his shop at 5 pm yesterday.

How can a simple job like this result in a rough idle? I would not describe the roughness as severe, but it is quite notriceable (enough to shake the mirrors) and definitly not there before the repair.

What is the best injector cleaner to get, is this worth a try, how often should they be cleaned with a fuel additive?

Any ideas appreciated?

ezrider.

I replaced one of these in the past due to a leak ... I got all six just in case. Not sure why the idle is affected, but if you do a search you will find all sorts of odd stories of weird hammering effects ... seems there are three parts that are replaceable ... I replaced two of the three.

There is a compression spring (did not replace), a copper seal, and an o ring - I replaced these two. It fixed my leak.

I gotta tell ya that the 350SDL I have is a sweet running engine with an occasional weird thing or two happening. One is that it is rough at idle (not always) and once in awhile it spits a bunch of smoke (can't tell if black or grey) while cruising at 80mph or so. I use injector cleaner (85+) a bit each tank and a good cleaning with a can about once every six months ... it burns no oil, is suitably fast for its vintage on diesel and is way comfortable.

All this said, I also wonder when it is displaying signs of spitting its guts out ... it appears from all the info available, to be the worst engine MB has ever built ... what a shame. However, I may stick with mine, drive it for as long as it works and replace the engine ... it is far less troublesome than the 140s (at least according to the web information available) and far easier and less complex to work on for the average guy.

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George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg

Have your mechanic re-torque the pressure valve holders. The copper seal can leak, resulting in rough idle -- I got my 300D cheap because #4 didn't fire at all at idle and #s 2 & 3 were weak. I replaced the seals, and found that #4 pressure valve holder was so loose I could unscrew it without the wrench!

What happens is that the leaking seal prevents pressure from holding in the injection line at low speed and low injection volume. The amount of fuel injected on the affected cylinder is low, causing rough idle.

The effect tends to disappear at higher speed, especially if the leak is minor.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

psfred, what is the "pressure valve holder"?

Thank you

Follow the injector lines back to the pump. The splined cylinder that each injector line attaches to at the pump is the pressure valve (or delivery valve) holder Peter mentioned. You need a special ~$30 socket to remove and install these holders.

Sixto
91 300SE
87 300SDL