I've posted this before, but got no responses.

I'm idling at about 750 RPM's. I've got bad compression on two cylinders, so it rocks more than a bit. If I bump and hold the pedal, getting me up to about 850-900 RPM's, it smoothes out considerably.

Question is, can I bump up the idle and not run into other problems? Secondly, where is the darn idle adjustment screw?

83 300 SD 172K "Goldie" Abused before I got her, but now being loved.

It might be more useful to adjust the rack mount screw on the injection pump...provided you can access it and there are any threads left. It's near the oil filter housing.

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Matt
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1995 E300 Diesel (Die Blau Frau)

I don't think it should do any harm. Will just keep more pressure on the trannie when you're at a stop light, which may make the trannie run a little hotter in a lot of stop and go traffic. May make it act kinda wierd as to going back to 1st gear too. Other then that, try it and see.

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past MB rides:
'68 220D
'68 220D(another one)
'67 230
'84 SD
Current rides:
'06 Lexus RX330
'93 Ford F-250
'96 Corvette
'99 Polaris 700 RMK sled
2011 Polaris Assault
'86 Yamaha TT350(good 'ol thumper)

Rickg/Zoonhollis,

I already adjusted the rack adjustment screw. I might need to go to a new spring on it according to my expert. Where's the idle adjustment screw?

Would you believe there isn't one?

Sixto
91 300SE
87 300SDL
83 300SD ... any takers at $1100?

Then I have to adjust the idle via the Rack Adjustment Screw?

On the inboard side of the injection pump there is an adjustment screw (#4) with a slotted head. Use a deep socket to release the locknut (#3) at the bottom.

Attached Thumbnails

 

Mine idles about 900, just under the 1K rpm.

I'd go out and check, but it's up on jacks in the garage 'cuz I can't get the rotor off the hub. I'm sending them both to the shop with the wife's minivan and let them have a go.

What kind of SD do you get for $1100? DON"T tell me. I'm waiting on a 300E 4matic sedan from a couple at church. Only has 244,000 on it.

Good luck!

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83 SD 143 K miles
93 Grand Caravan 130K miles
92 Buick Regal (winter car)

maybe you could try a different fuel supplier and run some power service additive through/change fuel filters and then see if the idle smooths out before trying to increase the rpm's. 172 k does not sound like a lot of miles at all on the engine. also what is your approximate location? as in what is the ambient temperature where the car is.

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1984 300D Turbo - 231k....totalled 11/30/07 RIP

So there is an idle adjustment screw? I thought only the non-turbo 617s had an idle adjustment screw.

Sixto
91 300SE
87 300SDL
83 300SD ... any takers at $1100?

Thanks speedy300Dturbo for the photo, it really helps. I'll keep you guys posted to see if it works for me.

Yup, if your rack damper pin is silver, it's the old one. The new one is somewhat brass / gold looking.

If my memory serves correctly (and it doesn't always....) the correct idle for most of our diesels is the lowest rpm that still gives a smooth idle. 700 to 800 seems to be the norm. Of course, the assumption is that everything is in proper running order. With a couple flat cylinders, you might not get a smooth idle until you really speed things up and I don't think your tranny (not to mention the rest of the drive train) will like it.

Wes

Is the rack adjustment screw the same thing as the governor idle adjustment pin?

Be careful when you try to loosen the lock nut for the idle screw. I really suggest soaking the lock nut + idle bolt assembly with WD-40 or something similar before attempting to loosen it if it hasn't been touched for a while.

DO NOT !!! Overtighten the locknut... I learnt the hard way...
You don't need to tighten it that much.

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2008 BMW 335i Coupe