Good afternoon,

Especially when its cold out, the idle on my 300D seems to move up and down at a constant rate. Maybe from 750 to 1000 or so. Not huge surging, just lightly going up and down at a very steady pace. As I said, it stops when the car warms up. I have heard another 617 do this as well. The rack itself is not moving.

Ideas?

Thanks,

dd

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

Try rotating the rack pin on the back of the IP out to the point where the engine starts shaking, then turn it back in slightly to stop the shaking and tighten it there. If this doesn't help you might need a new pin (also called governor idler adj. pin).

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

Agreed, but should show up after the engine has warmed up, regardless of outside temp.

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83 SD

84 CD

I already have a brand new rack dampener pin, adjusted just like you described. So its probably not that...or should I try turning it in a bit more to damp it?

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

I did the same thing, worked for a few months, then got really bad, was convinced it was something else. I had not properly seated the "O" ring. Have done so, no more problems.
I was readjusting, you back it out, the darn thing fell out! I shut off the engine, seated the "O" ring in the little recess in the lock nut.
Good luck, and make sure the bolt is properly installed.

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83 SD

84 CD

Bingo, fixed!! Improperly seated o ring for me too. Fixed it so far, although it hasn't been REALLY cold when the problem seemed to be much worse.

To re seat the o ring you need to take the pin out and push the ring back up against the lock nut. Its easy and obvious.

Glad this one seems to have been easy.

dd

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

I'm not grasping how an improperly seated o-ring will have any effect on the rack? Might leak a bit of oil, but, I can't see how it will affect idle.

Explanations??

p.s: The characteristic is called "hunting"..........and it's common when the governor is weak and cannot maintain a steady idle. The SD will do this slightly when it's brutally cold.

I dont understand why...maybe it keeps the pin from vibrating just enough to keep it from hunting?

My 617 would do this consistently when started under 40 F until it was fully warmed up (80 C coolant temp). It hasn't done it the last two days which have been under 40 but not under 30 ...so my sample size is small, but my results are fairly encouraging thus far that something changed based on what I did.

dd

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

Where, exactly, is this o-ring? I don't recall how it's installed?

It sits on the rack dampener pin between the IP and the rack pins's locknut. It seals the opening where the rack pin is inserted, and is held in by the locknut.

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

So, without the o-ring, the locknut would contact the housing directly and there could be a small amount of leakage between the nut and the housing?

I cannot fathom how this can affect the idle.

Mystery, I would love to see an explanation.

Reading your first post I would think you need to do the routine, valve adjustment, clean injectors, etc.

The act of replacing the o-ring and adjusting the pin resulted in the pin providing a different force on the rack..........it's slightly further out.........or further in.

This cured the hunting problem.

That's the only possibility that makes any sense..........the act of replacing an o-ring cannot affect the idle.

I can't explain it either, wish I could.
Bottom line, it worked.

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83 SD

84 CD