I picked up this car a few months ago and have gone through the front end and changed fluids,filters and done a general once over on the engine. Also changed the rack damper bolt which resulted in a super smooth idle. I usually drive the car around town and it runs nice. Today I took a 60 mile trip at 60-70 mph and when coming to a stop; the car started shaking pretty badly. The idle was steady on the tach and as soon as I gave it a little throttle, the shaking stopped. This went on all morning at every stop. Car would run smooth at speed but shake at idle. The thing that puzzles me is that it would also suddenly start running smoothly again as I sat at a stop sign. It would run rough for 5-15 seconds and then smooth out on its own. Any ideas?
Thanks
John

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1985 300TDT
2013 E350 Bluetec

It is likely a fuel restriction. My money would be on the strainer in the tank.

Dkr.

Thanks Dkr....I purchased a new strainer a few months ago and still haven't got around to changing it out. Guess it's time to get on it.

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1985 300TDT
2013 E350 Bluetec

And when the fuel restriction becomes infinite, the power and speed potential will also become infinite.

Have you run some biocide through it?

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Yes, I have run 3 tanks of fuel with Biobor as well as Power Service clear diesel tank cleaner. The car sat for 6 years and I'm thinking it may be too gummed up for this stuff to clean it. I may need to drop the tank and have it cleaned out. I'll pull the strainer after I burn through this tank of fuel and see just how bad it is inside and proceed from there.

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1985 300TDT
2013 E350 Bluetec

Could it be as simple as the air cleaner rattling against the valve cover? I had that and it shook the whole car.

I don't think so. The car "stumbles" at idle after a long trip but quickly clears up and runs smoothly. I'll check the air cleaner mount but I'm leaning toward a fuel starvation issue.

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1985 300TDT
2013 E350 Bluetec

I suspect backing out the rack damper bolt just a little may help.

I'll try that because when it was put in we screwed it in approximately the same as the one we took out and never did a final adjustment. I have to say that the cars idle improved so much that it runs pretty close to gas engine smooth.

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1985 300TDT
2013 E350 Bluetec

Startron has enabled me to never have to pull the fuel tank for cleaning.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

Have you changed the fuel filters since you ran the fuel system cleaners through it?

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'84 300D (211k) *New*... (Wife's)
'85 300TD (174K) 10th Year... (Mine)
'96 F-350 7.3L Dually (149K) Since New
'85 300D (156K) ~~~Wrecked~~~ Damn it! (parts)
'84 300D (176k) ~~~Wrecked~~~ Damn it! (parts)

Yes, filters have been changed, diesel purge done also. I'm going to try the rack damper bolt adjustment as a first attempt. The tank strainer may be plugged but after the trip I checked the clear primary filter and it was clean. Also it was full of fuel and no bubbles were present while the car was running. I never adjusted the rack damper because the car was idling so well I didn't think about it.

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1985 300TDT
2013 E350 Bluetec

As the primary is clear and full... I doubt its the tank filter but that's always low hanging fruit so have at it.

Most of the issues I have seen are with the secondary fuel filter (spin on) as they tend to trap more gooo (paper filter) from fuel system cleaning. There were about a dozen or so of us from about 07-10 who produced our own bio-diesel... which is a very good fuel system cleaner and has much better lubricity than diesel fuel. It wasn't unusual for someone to change thier secondary filter 3 or 4 times through the first 10 tank fulls or so as the paraffin sludge dissolved and passed through the system.

Rack Damper - Is this occurring @ an idle of 750rpm? I need to adjust the idle on my '85 TD... it's about 600-650rpm ...it's smooth but that's a tad slow when the AC compressor kicks in.

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'84 300D (211k) *New*... (Wife's)
'85 300TD (174K) 10th Year... (Mine)
'96 F-350 7.3L Dually (149K) Since New
'85 300D (156K) ~~~Wrecked~~~ Damn it! (parts)
'84 300D (176k) ~~~Wrecked~~~ Damn it! (parts)

I should have mentioned this before... Injectors. There is good debris and bad debris. I never *flush* my transmissions... I change the fluid (including torque converter) and replace the filter but I want to leave the microscopic debris that has formed around those tiny valves.
The same for Injectors whether some sludge from the cleaning gummed up the works or some good debris got washed away it can change how the Injector fires... i.e., is an injector firing @ 150bar or 120bar ...they should be firing @ 135bar. (1958 or so psi)

I'm personally not a fan of the mechanic in a can type of maintenance... as it has *never*, *ever* worked for me.

Just good info below... that may describe your problem (although I would not buy the product).

Why Does My Diesel Shake So Badly at Idle - Part 1 Fuel Injectors
https://www.youtube.com/watch?v=rAOVL3C0dvg

Why Does My Diesel Shake So Badly at Idle - Part 2 Fuel Injectors
https://www.youtube.com/watch?v=7cdyiy4g930&t=320s

The videos go on...

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'84 300D (211k) *New*... (Wife's)
'85 300TD (174K) 10th Year... (Mine)
'96 F-350 7.3L Dually (149K) Since New
'85 300D (156K) ~~~Wrecked~~~ Damn it! (parts)
'84 300D (176k) ~~~Wrecked~~~ Damn it! (parts)