Hi folks,

Been living with a shakey idle for a bit now. Before everyone suggests the obvious, here are steps I ve taken to improve things.

- Valve adjustment
- Injector rebuild by Greazzer
- OFV spring replaced from one by Greazzer
- Engine mounts replaced with Lemfoerder ones
- Driveshaft rubber mount and bearing replaced
- Flex discs changed with Originals
- All front suspension components replaced with new ones (no chinese parts)
- New hand primer pump

I have a pretty smooth sounding idle - as in it sounds reasonably quiet and revs up very nicely
There has been a significant power improvement since doing the injectors, spring and valve adjustment.

However; my idle both in P or in D is lopey. The engine sounds perfect but there is an obvious shake.

I have some ideas but they might be stupid so all of your wisdom would be greatly appreciated.

1. I have my A/C compressor disconnected. It doesnt work so I took the belt off. Is it possible that having a heavy object hanging from one side is causing the engine to vibrate?

2. Could there be an actual issue with the injection pump?

3. My belts are tight but is it possible to over tighten them and cause vibrations?

Here is a not so good video of what I m trying to explain. As you will hear from the sound, the engine sounds great and there is substantial power but I d really like to have a smoother idle.

https://www.youtube.com/watch?v=YFf2zr1SSQU

4. Am I being an anal idiot and comparing it to modern/gas cars?

Thank you all in advance for your advice.

Order a new rack damper bolt and adjust it properly.

It has a spring in it that wears out.

It is a maintenance item, like the OFV.

These 617's can idle smoothly.

Unfortunately Mine is a NON-Turbo so no rack damper bolt. There is a bolt on the back but I m pretty sure its not a rack damper.

Although I ve never tried moving it.

I don't think it is turbo specific

It is.

Was there an engine damper for this year/model? If so, was it replaced?

I found the best thing for my old 300D's idle was a valve adjustment, but sometimes I had to do it more than once to get it right. I always suspected that there might be some valve seat damage, but it didn't bother me enough to pull the head.

You might want to check your engine compression. If there is enough of a difference (imbalance) between cylinders, nothing you do will bring the idle to complete smooth.

Dkr.

This is something I have never done so maybe a compression tester is in my future.

Lets say there is a substantial imbalance in compression values between cylinders, whats a reasonable course of action? What would be considered substantial imbalance. I assume no OM617 out there - unless meticulously maintained would have exactly equal compression on all cylinders, right?

FYI, my car starts excellent in the morning - cold/hot/whatever. I have a upgraded pencil style glow plugs. Never changed the relay so the glow cycle is just as long as it used to be with the old loop style ones; however the starting performance is amazing. Wouldnt this indicate decent if not good compression?
Also, from your experience - is it possible to have smooth power delivery/more power with unequal compression, as long as everything else works fine?

MXFrank, thanks for the suggestion. I am due for another valve adjustment in a couple of months. I ve done valve adjustments myself in the past and they were never totally perfect. Now I let my local mechanic do it since hes much better at it and is an OM617 guy as well. Its not too expensive and is worth paying to get it done right for me. Hopefully the next adjustment will improve things a bit more.

Thank you all for the suggestions. Any other advice would be greatly appreciated.

The car is old. I would want to make sure the fuel pressure is adequate in the base of the injection pump. When low the idle is not quite as smooth as the power balance seems impacted. A quick test is to close the relief valve fuel line from the relief valve. If the idle is a lot better do the relief valve spring. I was also wondering about air getting in the fuel. It has a more profound effect at idle.

Something that should be checked anyways. Many times there is a problem with a sagged fuel pressure relief valve spring with age.

Or the fuel lift pump is getting tired but I doubt this from parts of your description. It is still possible but not that probable. I think I would borrow or get the cheap harbor freight compression gage and get a baseline on that engine. If the relief valve first test show shows no difference post that as there are subsequent follow up tests. Since it starts very well cold is a good sign though.

You need to check your valve lash before you check compression. Uneven compression can be caused by rings, valves, or damaged castings. If you discover a compression problem, you would then need a leakdown test to zero in on the cause.

I'd also suggest doing easy things like checking fuel pressure and injection timing before you go looking for major engine problems.

I've heard a variance of 10% is acceptable. If you have more, there may be nothing wrong with the car and it and the engine may still have a long life ahead of it, but you may not be able to get the idle where you want it. I think in general, the course of action would be to live with it unless you want to throw a substantial amount of money on making the perfect idle.

Dkr.

Thanks for the great suggestions folks!

I think I will check the injection pump timing this weekend as well as do a compression test. Will post the results once I get them.

I have a new relief valve spring so thats definitely good.

Unless something drastic is revealed through those tests, I think I will leave things alone and just live with it.

Too many times have I gone after some small issue that was bothering me on this car and ended up with massive hits to my finances.

BTW, the lopey idle really started after I had the injectors rebuilt. While they definitely increased power and smoothed many things, it probably unveiled some other issue that needed attention but was hidden by the worn out injector nozzles and sluggish performance.

Will keep everyone posted.

Thanks

An easy test is to try running a full tank of Propel Diesel HPR. It is available in LA. My two 300D's idle noticeably smoother on it. Being bio-based, it might also help clean the lines and injectors. It is compatible with all diesels, even new ones. If it helps, but no station nearby for normal use, many say that B20 gives similar benefits or similarly just pour a quart of vegetable oil in each D2 fill-up. I suspect that bio-diesel will be everywhere and cheap soon in CA, due to carbon credits and several plants being built to supply airlines.

__________________
1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

Thanks for the suggestion Bill.

I have been running almost exclusively on HPR for the past 5 or so months.

My engine idles nice and quiet and almost sounds like an older gas car. In fact with the windows down, I often hear the engines from cars around me more than my own.

Its just that there is a lopey idle.