Continuing Vibration at idle
 

Well, I've done quite a bit of work on my 1983 300D and I still can't get the vibration at idle to go away.

Here's all I've done:

Valve Adjustment, transmission mount, new rack damper screw, cleaned out the alda line that goes to the intake (it was sooted up), two bottles of diesel purge through the fuel, resetting the linkage rods

The only major thing left is the engine mounts, which I haven't mustered up the money to pay for yet. But, they're dry and don't LOOK to be very bad, but looks can be deceiving.

That being said, I'm still getting a pretty decent vibration at idle, it's much worse when the car's cold, but still there when warm...all times it's worse when the A/C compressor is on.

No matter what I do, I can't get an idle of more than about 600 rpms.....is there any way on these cars to increase the idle speed?

Also, would worn injectors (or nozzles) cause rough idling like this?

Thanks,

Joe

Yup replace those engine mounts,I dont have the DTs anymore on my engine:D

The above in blue is an indication of something going on in the Combustion/Precombustion Chamber. The Fuel is burning better when the Engine is warm so it vibrates less.

I did a whole list of things to get rid of idle vibration; including changing Trans and Engine Mounts. But, the 1 thing that I did that took out the bulk of the vibration was rebuilding my Injectors.

The stock Injector Nozzles have holes drilled in the little Pintel inside of the Injector. On the set that came out of my Engine and almost all of the ones I have pulled from the Junk Yard those holes are plugged with carbon. (The FSM shows taking the Injector apart and picking out the holes with the proper sized music wire.)
Below are 2 pics; the drawing shows how the holes are drilled. On my I jectors even the bigger cross drilled hole was plugged.

If you are also having hard starting and smoke at starting there could also be an indication of poor compression.

Also it was not until I did the list of stuff to reduce vibration that the new Gold Colored Rack Damper Screw was able to help.

Yes, all the stuff you did is a good start but if the injectors are causing the rough idle, nothing will fix it until you fix the injectors. If you REALLY want as smooth a ride as you can get in this car, change the motor mounts and rebuild the injectors. If you have limited funds, I would bet the injectors make a bigger difference than the motor mounts.

FWIW. I have done injectors by Brian Kast, valve adjust and engine shock on my 82 240 and it still rattles and clanks at idle. The mounts all look ok not cracked or obviously compressed and they still seem to be keeping the belts and pulleys away from the cooler lines.

My attempts so far:

New filters
Diesel purge
Multiple valve adjusts
New nozzles w/shim,balance
Engine mounts
Trans mount
EGR delete
Delivery valve seals
Rack damper update
Primer hand pump update
Lots of DieselKleen
Timing check (eyeballed to be OK, balancer is inverted :mad:)
Engine shocks are next

Still shakes like it has Parkinson's at hot idle.

I doubt engine shocks will do much for this... they mostly work for engine shutoff and on.

Have you done a compression check? Might be a bad cylinder, stuck ring(s), or something of the like.

These cars idle higher when cold, so there's also a chance your hot idle is a little too slow for the engine's liking. A warm idle speed of 600 might just be too low, try 700 and see if that helps. Idle speed is set with a screw on the engine side of IP on your car, I believe. Check the FSM for sure.

I plan to up the idle speed a tick tonight to see what happens.

If I had my options, I'd rather work on the injectors, because I can do that at home, rather than paying for labor.

Are we talking about a complete rebuild of the injectors, or a changing of the nozzles?

If you put new nozzles in your injectors, you're basically rebuilding them if you get the shims, pop pressure and spray pattern right.

You have to check the spray pattern and pop pressure before reinstalling- if not, your problem might be worse than before.

It would be cheap to bring them all to a shop and have them checked, that way you know the offending injectors. An alternate (and imprecise) way to check them is to loosen your injector hard lines one at a time and check the effect on idle that way.

Opening injectors and replacing nozzles precipitates the need for a shim and balance IMO.

From my hours reading threads about the shakes, it seems that almost no two cars have the exact same fix for it, barring perhaps the rack damper and injectors. Those do seem to sort out a fair percentage of the complaints. Beyond that it's a hit or miss proposition. Mounts have done it for some folks. One guy had a hairline fracture in the spin-on fuel filter housing allowing air. The old-style fuel hand pump is known for that too. One did report that new engine shocks worked for him (and I know mine are shot from when I did the mounts). One found out he had low comp on every cylinder, but one was really low. That's just what I can recall quickly. What we really need for this issue since it's so common, is an ordered list of things to check ranked by how often it helps and how difficult/expensive it is to check and correct.

I believe my car does have a cylinder/ring issue. I haven't simultaneously had the time and inclination to check the compression since finally getting a tester, but it has run VO (details unknown) in the past and cyl 5 wasn't firing when I got it (is now), so I'm hoping for stuck rings. I suppose too I haven't done the comp check yet because I KNOW #5 would show weirdness. Moved right to trying to improve it without a rebuild so am running a heavy dose of MMO+DK in the fuel. Since it actually seems to be showing some improvement from that already, the comp test is looking good for this weekend and may even do a before/after with some MMO soaking in #5 overnight. It does smooth out with pretty much any throttle, but I hesitate to simply up the idle speed since it would just be masking the problem.

That is the same thing. If you put new nozzles on you will want to pop test them to make sure they are all within the same spec. You can build you own pop-tester for well under $100, less if you get a deal on a pump. Do some searching on here as there are pictures and instructions of how to do this.

I adjusted the idle speed to about 750 and the vibration is largely gone at idle...it comes back somewhat when I'm in Drive at idle. I have some nailing one of the injectors, no doubt...I think it's the second one from the front of the car.

I might just buy a set of reconditioned ones rather than have a shop around here do them.

Contact BGKAST to have your injectors done. they will be done right, not some off the shelf rebuilds.

Charlie