Hello everyone and a very pleasant Sunday afternoon, too!

My 250 TD engine has developed this problem : when the engine is cold or hot, when on idle, it every now and then (sometimes it does, the other times runs perfectly still) starts to vibrate so much that the whole chassis vibrates along. All I need to do is to press on the gas and let go, the engine revs up, then the rev number returns to what it was before and the engine idles nicely, no shakes.

I start moving, stop at the next lights, select neutral and the engine vibrates again. I press the pedal, let go, the engine idles as it should. The vibrations however also happen when a gear is selected and the brake depressed. At low RPM so to say. On reverse the vibrations are felt at worst.

I have increased the idle RPM value on the injector pump, now the engine runs at 900 RPM which is a relatively high value but the shakes don't go away.

What things should I be looking for? Some kind of vac leak? The transmission shifts nicely though, air and fuel filters are new, bowden linkage gas pedal <-> injector pump runs well, injector spray pattern already checked for.

Thanks!

Since you have already checked the filters etc. , it sounds like either a vacuum leak or bad engine mount and/or engine shock.
Check all vacuum connector- the rubber connectors. Also visually check the engine mounts.

I would also do one more thing. A good quality (like rotella DFA) diesel fuel additive or anyother similar product that has fuel injector cleaning property should be added to little less than half the tank of good diesel. Run the car for a good 50-100 miles at a stretch asn see if that takes care of the vibes. good luck

MVK

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One penny saved is three penny earned.

1985 300D Turbo 179,000miles

Could you tell us what year and model? Makes a difference -- the 617 engine, especially later turbos, has an idle shake problem that can easily be resolved. The 602 doesn't have either the problem or the easy fix!

On any engine with considerable milage, the engine shocks are probably bad, or engine mounts, or both -- this allows engine vibration to reach the chassis instead of being absorbed by the mounts and shocks as it should be.

You can check by watching the engine, hood up, when it shakes. If it wobbles at lot, suspect bad engine mounts, it shouldn't move all that much even if idling rough.

Check the location of the fan in the fan shroud -- if it is near or on the bottom, the mounts have collapsed -- they will look flat, and some of them are fluid filled, when they go bad they leak oil.

Engine shocks can only be tested off the car, but if the mounts are bad, the shocks usually have been beaten to death by the engine sitting too low.

The mounts on my "new" '72 280 SE had dropped at least an inch and a half -- one shock was bent (!) and the other had no oil in it. New mounts and shocks and I cannot feel and idle vibration at all, although I can see some in the engine (bad fuel and sticky injectors).

Peter

__________________
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:

would you please enlighten me as to the easy fix for the later 617 turbos to solve the idle shake? Mine does it sometimes, and Id love to solve the problem...
Thanks

JMH

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Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
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1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)

My 601 does the same thing... MB told me the engine was fine, and it did that before I took her in... I just assumed it was normal.

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1984 190D 2.2 Auto 220k
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JZH,

I'm not sure if this is what psfred was referring to as an "easily resolved" fix for a shaky idle, but here is a simple remedy:

At the rear of the injection pump is a rack damper bolt. It sits snugly between the IP and the oil filter housing, so it's not exactly a breeze to reach. If in your case there is any thread showing on this bolt, simply screw it inward a little at a time until your rough idle problem disappears. If there is no remaining thread, you may be able to purchase a new one.

This is NOT to suggest that you do not have other problems related to your rough idle, i.e. bad mounts and engine shocks, but it's a fairly simple procedure, and it might well be the cause.

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Matt
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1995 E300 Diesel (Die Blau Frau)

Matt:

That is exactly what I was thinking of.

However, you need to do the following first: Check engine mounts -- if vibration is significantly less in reverse than in drive, fix mounts, they are bad (the left one, I think, lasts longer because engine torque pounds the right one down more).

Verify that you have good injectors (minimal smoke, good starts, good milage, no serious knocks).

If every thing is fine, but you have excessive vibration at idle only -- goes away completely if you open the throttle even a little, the rack bolt needs to be adjusted. It isn't the bolt, really, it's the spring on the other end, but to fix that requires an IP rebuild ($1200 or so at least, and why rebuild the pump for just rough idle?).

Proper procedure is to make SURE the engine is at full operating temp, in drive with the brakes on hard, plus parking brake (you don't want it to run away from you driverless!), then unlock bolt and slowly screw in until idle smooths out JUST enough for you to tolerate it. You aren't going to get is totally smooth, most likely, and if you overdo it, you won't be able to start it cold.....! Lock screw down, then bump the throttle hard, then recheck idle smoothness. If still too rough, adjust in some more. It is very necessary to run the engine up against the brakes to check -- leaving it in neutral will result in under correction.

If you then have hard start problems, the spring is so bad you will have to live with the vibration until something goes bad enough in the pump to justify an overhaul, or replace the pump.

Remember, a bad engine shock will look just fine, but no dampen vibration -- they are much cheaper than pump repairs! So are engine mounts.....

JMH:

Occasional is how this starts out, usually it gets progressivily worse with time. Bad mounts will do the same thing, especially later gel filled types.

19022:

The 601 has gel type mounts, replace them and your problem will most likely go away. The mounts are ovalish when good, spherical to flattened when bad, so if the look droopy (or leak oily stuff), replace them. Do the engine shock, if you have one, at the same time.

Peter

__________________
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, are you a mb tech by any chance? I have seen you answer a couple of my friends posts when they got stuck, who are quite knowledgeable.

Tank:

Only on my own cars, but I spend way too much time yakking with my friend, MB factory trained Master Mechanic (Dusseldorf, 1972) who moved over here in 1983. Great fun, and I learn a lot.

Besides, these are really very predictable cars -- you just have to get to know them!

Peter

__________________
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!

Thank you all for your suggestions. I have already suspected engine mounts. They look good. I know this doesn't mean they are but ... if they were bad the engine would vibrate all the time when on idle I suppose. Not only every now and then.

Can the engine shocks be changed without having to raise the engine up? I don't suppose one would need to completely remove the engine to do so.

The engine is a 602 (2.5l TD), 120k miles, there are no visual defects, also all rubber connections look good, the rubber as new. I already have increased the idle with the screw on the IP, doesn't help. It appears that the shakes have no direct relation to idle RPM. Originally RPM was ~750, I increased them to 900, the shakes disappeared but only until the next drive when they re-appeared. There is no (significant) smoke from the exhaust, no nailing, starts immediately).

As for the injection pump, it's all clean. It used to have a leak from the top, between where the injector line sits on the top of the IP. It was only a minor leak but one could smell diesel inside as it accumulated under the hood. I fixed that and IP leaks no more. There are no other leaks and the pump is clean. I could have the pump removed and rebuilt ($200 for both labour and complete set of gaskets for the IP at Bosch service) but wouldn't really want to have the IP removed from the engine, one has to remove a lot more things from the engine than just IP itself to have it out.

"If every thing is fine, but you have excessive vibration at idle only -- goes away completely if you open the throttle even a little, the rack bolt needs to be adjusted. It isn't the bolt, really, it's the spring on the other end" - this describes the vibrations quite well. I don't suppose one could just unscrew the bolt and change whatever part is needed (the spring on the other end e.g.) without having to take the IP off the car?

Fred, I already did the procedure with adjusting the idle with gear engaged, braked, moved the bolt until vibrations disappeared, when pulled the throttle cable, after the engine reved down the shakes started all again. Surely enough, they disappear when the idle is at 1000 or more but I find idle of 1000 neither acceptable nor normal.

Thanks again for all response, it's well appreciated.

I don't think you could have done the rack bolt adjustment on the 602 pump, it doesn't have one!

Jassper

The 602 turbo has electronic idle speed control. The selector is on the firewall, probably up by the brake booster. A black "plug" with numbers on it, usually has #4 lined up with the index. Pull it out, rotate, and plug back in on another number -- if the contacts are loose or corroded, you may be getting very low idle speed, or erratic speed control. I would undo whatever you did!

Also, what did you do to fix the fuel leak at the "top of the pump" (obviously the pressure vavle holders)? This is usually the 0-rings on the pressure valve holders, and it is important to get the pressure valves torqued properly if removed -- mine were only hand tight (!) and caused an internal leak, making the car shake something terrible. Cheap and easy fix!

You do not want to remove the IP, requires several special tools, and there is nothing worng with it that I can think of from here. Leave it be -- and a rebuild will cost $1200 and up, especially if you bugger it up taking it off.

Peter

__________________
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!

Hi Peter,

'I don't think you could have done the rack bolt adjustment on the 602 pump, it doesn't have one!'

Aww my! What is this bolt (screw secured with a nut) on the back of the IP, opposing the firewall? When I loosened the nut and turned the screw the idle rotations increased or decreased.

I shall look at the selector today and let you know what I found. I can't remember there is one though.

The interesting thing is that yesterday, as I read all replies, went to see the car to think what could be done about it and ... she ran fine all day long! No shatters at all. Can't be the mounts. However, with the end of the day the shakes started all again. I also thought this might have been caused by a vac leak but when I disconnected the line that cuts the engine off (moves the red STOP lever down) (several hours after having stopped the engine) there was still vacuum, I could hear hissing sound for over a minute. If that vac system is interconnected with the one that controls transmission there can be no leak.

My second thought was the causer for all of this might be that recently I hooked the front lights to vac (to be able to raise and lower the lights, depending on load) - found a rubber Y piece which I connected between the vac lines and also hooked the lights vacuum switch between them but that system also has no leaks.

"Also, what did you do to fix the fuel leak at the "top of the pump" (obviously the pressure vavle holders)? This is usually the 0-rings on the pressure valve holders, and it is important to get the pressure valves torqued properly if removed "

Well, on the top of the pump the metal injector lines connect. The line goes into a cone thing that has grooves all along its sides- obviously for adjustment by rotation. The cone thing is secured by a metal ring with a screw (with paint seal on the screw). The ring is there so that the cone thing couldn't be rotated and thus adjusted illegaly I figure. When you unscrew the screw and lift the ring from the grooves you can rotate the thing. The diesel leak was from where the cone thing was screwed in to the top of the IP, beneath the metal ring that secures the thing. (Excuse my ignorance but I have no idea how to name these parts). As I suspected the thing with the grooves ought not be moved (so I was told by a Bosch mechanic who does IPs only) because that's how one adjusts the injection parameters, (my first thought was to screw the thing tighter but that would also change injection I was told), what I did was to remove the metal ring to get access to where the IP and the thing with grooves meet and pour a rather thin layer of liquid sealant all around the grooves and then put the metal ring back on. The sealant turned hard and I have leak no more. Naturally, if it was an internal leak this was no remedy for that.

"You do not want to remove the IP, requires several special tools, and there is nothing worng with it that I can think of from here. Leave it be -- and a rebuild will cost $1200 and up, especially if you bugger it up taking it off."

It takes special tools indeed, MB have 6 hours for removal and back mounting of an in-line IP (with the cost of $13.50 per hour for a W124 that makes $81 just for the removal and as I said to have the IP rebuilt with a compelte new sets of gaskets, the Bosch service ask $200, labour and new gaskets inclusive).

I will check for the idle selector but if it is a round plastic dial then I don't have one.
***************************************************

Right-o! This is I again, several hours later. As suspected, there was nothing beside the brake booster (or anywhere else) that resembled the dial. I know there is one (wired across with a lead seal) on my Dad's car but that runs on petrol.

Interesting to notice however is that the engine is smooth now apart when I put the selector to reverse. Immediately the engine starts to vibrate heavily. Any suggestions?

Also I noticed that overnight the vac leaked - the red STOP lever was up. This takes several hours though. I wouldn't expect the system to retain vac for ever after the engine is off. Or, should I? Do you think this is normal or is there a leak after all?

Jassper,

I recently underwent the task of chasing down leaks in my vac system, and I got a lot of good pointers from the archives here. I found that the plungers on the door lock bellows were cracked and leaking, so I fashioned a fix with yellow dishwashing gloves. I now have 100% vacuum on my 300D, and it's a pleasure to actually USE the door lock features the way they were meant to be.

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Matt
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1995 E300 Diesel (Die Blau Frau)

Jassper:

In order of importance: The "grooved things" on the IP are the pressure valve holders. They don't adjust anything (there are IPs that have external adjustments), but they do hold the one-way pressure retaining valve for the injectors. What is leaking (or was) is the o-ring at the outside of these -- seals the low pressure fuel chamber in the IP. You can take these out to replace the o-ring, but you will need new copper seals and must tighten them correctly. They are locked with the rings so they won't vibrate free.

I still think the 2.5 turbo is electronically controlled, so there should be an idle speed controller somewhere -- the 603 (3.0L) turbo certainly is. You do have a turbo, don't you? It is possible it is not, but I would guess it is. You may have adjusted the maxumim fuel delivery instead! Who knows, I will ask.

I don't believe a rebuild for an IP for $200. That would barely cover gaskets and gasket replacement, certainly no test bench time or adjustments beyond minimal fuel delivery testing. Unless you don't have a electronic pump, but that is still VERY cheap!

Your cutoff lever should stay down until the key is turned back on. You need to check for leaks, can be in the hoses, rubber connectors, or in the shutoff solenoid. Fairly easy to replace (you can do it without removing the intake manifold on the turbo version).

I would T the vac supply for the headlights in at the main accesory T at the front of the engine at the vac pump -- it won't hold vac with the engine off, but will also not screw up the rest of the vac system.

You will need to lift the engine to change mounts and engine shock(s). If the old mounts are bad, it is sitting pretty low now.


Peter

__________________
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!

This is an interesting discussion : as for the idling speed control of 603/602 engines, I've just checked my CD. On all models it is electronically controled : the speed is ajusted by an actuator on the back of the IP that receives a signal from the EDS control unit, who in turn receive a signal from a speed sensor on the starter ring gear. But there is also an "ajusting screw for idle speed" on the back of the IP. That would be the one that Jassper talked about.

As for the electronic "idle speed" ajusting device refered by Peter, the CD talks about a "resistance trimming plug for idling speed" that was fitted on model year 1986, 1987 and 1989 (W124, W126 and W201). All diagrams from 1990 and up related to US models don't show that device and I didn't find it on my car.

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DR
1992 300D 2.5T 351 000 km