Hi all,

A quick question about my recently acquired landbarge ('84 300sd). At idle, especially while conld, it shakes pretty significantly. While cold, the airfilter housing rattles all over in the engine bay, and while sitting at a red light, it is enough to shake the entire car noticeable. Is this normal? I do have to adjust the valves (I don't know when it was done last, currently 111k miles). Could I have some sort of misfire?

Thanks,
Jack

There are many things that could be (causing/contributing to) what you describe:

1. Dirty fuel filters
2. Misfiring injector(s)
3. Worn out or broken motor mount
4. Broken air cleaner 'feet' (excessive air cleaner movement)
5. Idle speed set too low
6. Idle not correctly set up (idle speed and rack damper bolt adjustment).
7. Valves out of adjustment
8. Bad fuel

And I am probably forgetting something.

Did this come on suddenly or just creep up? How is the car performing generally?

Do you have any history on work done to the car before you owned it?

__________________


Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Does the car smooth out while moving? If you are shaking in drive while stopped and you switch it to neutral, does the shaking stop?

I had the same issues with my 1991 300E with 175K on it and changed the 2 motor mounts and now the car feels like it's not even on!

IT doesn't seem to change when in neutral, I had that thought too. I don't have any maintenance record, and I just got the car about a month ago. It's happened since I've owned it. I have changed both fuel filters, and put about 2.5 tanks of fuel through it. I am going to adjust the valves this week, along with hopefully getting to the bottom of my hard 1-2 shift (adjusted modulator on trans, helped some, but still some intermittent hard shifting.)

I'll write back with results from the valve adjustment. And what should I look for in a worn out motor mount?

Thanks,
Jack

The small passages in your Injectors #12 at #14 and #15 can get completely plugged with Carbon. You idle Fuel quanity is supposed to go through those passages.

Rebuilding the Injectors and the Valve Adjustment took away the largest amount of shaking on my Car.

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84 300D, 82 Volvo 244Gl Diesel

to add to Zacharius' list.
9. Bad rack bolt or adjustment.

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1982 300SD " Wotan" ..On the road as of Jan 8, 2007 with Historic Tags

My first instinct is always dirty injectors, based on previous lists in which I participated, but on this list I've read lots of posts that led people into other issues so I hesitate to sound too sure about anything....

I would do the valve adjustment and see if that makes a difference. I suspect it will probably help but what you are describing would be a bit extreme for just valves.

Assuming the shake is still there, I would suggest running one or two bottles of diesel purge through and see if that smooths it out. If it does, then you need to pull your injectors and get them professionally cleaned by a Bosch injection service centre or, preferably, have new nozzles installed.

The DieselGiant site has a how-to on diesel purge: Diesel Purge Mercedes diesel maintenance tips

In my experience the benefits of the diesel purge tend to be short-lived (a few days to a few weeks at best) if the problem is a long-standing one. You will need to get the injectors serviced or rebuilt for a lasting result.

__________________


Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

I would also pull the Rack Damper bolt. After coming off of high-speed highway runs, my car would 'lope' once I got to an idle at a stoplight.

When I pulled the bolt (which was an updated, but aged cad-plated one), the tip had been worn down. Put in a brand new bolt I had in the parts bin, tada! No more lopey-shakey at the light.

__________________
'85 300TD "Puff The Magic Wagon" - Rolling Resto
'19 Mazda CX-9 Signature - Wife's sled
'21 Morgan 3-Wheeler P101 Edition
'95 E300d - SOLD
'84 300TD "Brown Betty" - Miss this one
'81 240D "China Baby" - Farm grocery getter

Do all of the free and cheapest stuff first.
From what I have read the first thing people suggest is a Rack Damper Bolt.

However, that did not work for me. I bought it and it had almost no effect when I adjusted it.

After I did the valve adjustment, replaced Motor and trans mounts installed the Rebuilt Injectors the Rack Damper was able to remove a little bit more of the shake.

I also replaced one Engine Shock but that was because I damaged mine.
I found that I had a small Air leak that only showed up when the Engine was hot. As it turned out my Fuel Inlet Hoses were hard and inelastic and for some reason did not seal when they got hot.

Cheap replacement with 5/16" Fuel Hose that any Auto Parts store sells cured that.

If the Injector passages #14 and #15 are entirely plugged with Carbon I do not think a Diesel Purge is going to flush it out.
(The manual shows using specific sized Music Wire to pick it out.)
However I believe periodic Diesel Purges will keep the passages open.

If the Injectors are apart an Ultra Sonic Cleaning Tank is what a Fuel Injection Shop would use to clean out the Carbon and the Music Wire if the Tank did not clean them.

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84 300D, 82 Volvo 244Gl Diesel

Thanks guys, this is the best. What an intelligent forum. I'm going to adjust the valves on Friday, since that needs to be done anyway, then start moving down the list, starting with the cheapest fixes.

It's strange how intermittent the problem is. Sometimes, it's relatively minor, while other times I feel like I'm driving a funny car.

Thanks again.
Jack

Ahhhh, okay if it's intermittent then have you found a commonality to when it occurs?

If, for example, it's after extended highway use (and returns to a smooth idle after a while once you are off the highway), that isn't that unusual. It's probably wear in the pump governor. My first SD did that all eight years I owned it.

If the behaviour is related to ambient temps, or engine temps the longer you drive, then it could be an idle speed adjustment/rack damper bolt (adjustment or wear) issue. Rack damper bolt wear means you need to upgrade to the gold bolt.

Just to further complicate things: I forgot in my original list to include air leaks in fuel system. But that would produce fairly constant symptoms, albeit likely worse with the motor fully warmed up.

__________________


Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Hi folks,

Just finished my valve adjustment (definitely do have to bend at least one wrench, no matter how stubborn you are). It made a massive difference. The engine idles much smoother, and runs much quieter and more responsively. Almost all the valves clearances were tight, so I got them to spec (erring to the high side). Not a bad job at all once you get the hang of it. Next project is pads, rotors, brake lines, and trying to soften that 1-2 shift.

Thanks all.
Jack