In the last few days my 1985 300D has been very sluggish until it hits boost, at which point it picks up quite suddenly and feels normal. In other words it seems to struggle in the low rpm's until about 2200rpm where the boost comes in. Also, as soon as the rpm's drop below about the 2200rpm range the boost goes away very quickly and the car suddenly feels like a brick with less power than my former 240d.

For example yesterday on a medium grade hill i had it floored and it wasn't accelerating past about 1700rpm with the pedal floored. I had to manually downshift at which point it did slowly accelerate to the point of hitting boost.

Also, when starting from a stop it feels similar to how a manual transmission car feels when you try to start from second or third gear, very little torque until the rpm's slowly start to creep up.

On the other hand once on the freeway it accelerates easily to 75-85mph and runs like a top with the RPM's in the 3k range.

A few things I've done recently:

* rebuilt my front suspension
* new starter
* dsconnected and capped-off the EGR
* had to reconnect the vacuum hose going to the transmission at the transmission (not sure how long it had been disconnected)
* replaced a few vacuum connectors that were worn out and possibly had holes in them, particularly at the 'blue flying saucer'.
* replaced the air cleaner bracket

A few thoughts on what it could be or what i should try:

* probably wouldn't hurt to change the fuel filters, but they have been changed about six months ago
* is my kickdown switch not working?
* could the recent vacuum hose work be messing with transmission shift points, e.g. preventing it from downshifting?

Any wisdom here is appreciate.

I'm experiencing very similar issues with an '85 300TD

The first point to check is if the throttle linkages are actually moving properly, under the hood.

Have someone sit in the car (not running obviously) and push down on the accelerator pedal gradually until it reaches the floor.

You stand and look under the hood to see if the linkage is moving properly in response. When the pedal is on the floor the vertical pump linkage should be at its full travel.

Two suggestions: (1) that work you did you may have accidentally caused something in the linkage to bind or catch and limit or slow its travel, or (2) that the big rubber throttle bushing at the firewall has come detached and is limiting your actual linkage travel under the hood. If the latter, you have to replace the assembly, though JB Weld will hold it for a few days or a week if needed.

A car with that bushing separated will drive like it's towing a flatbed of bricks. In effect you are getting 1/3 of the pedal input reaching the injection pump.

Edit: Auspumpen, I read your linked post as well and I suspect these are different issues the two of you are dealing with....

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Sounds like your ALDA capsule popped.

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James Marriott
2003 Buick Regal
1983 300D (228k, frau Auto)
1996 Suburban K2500 (192k, 6.5 turbo diesel/4WD towmaster 10,000)
www.engineeringworks.biz
1987 300SDL junker 170k
1982 300SD junker, 265k

No where did you mention cleaning the Boost Line or Banjo Bolt at the back of the Intake Manifold. The Banjo Bolt gets gunked up from the crud inside the manifold, deposited by the EGR dumping soot, and blow by oil from the VC.

Remove the Banjo Bolt, there are 2 aluminum washers don`t lose them. clean it out and blow out the boost line with Brake Cleaner, and some compressed air. line runs over to the Switch over Valve next to the Brake Booster. then the line goes over to the ALDA.

(Be sure to disconnect line at Switch Over Valve before blowing out line)

If this line is plugged, you will develope the systems you describe.

Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

Thanks for the replies.

I checked the throttle bushing and it is indeed torn, although not completely separated. The linkage was definitely not traveling as far as it should with the pedal all the way to the floor.

I have the bushing in a clamp with some jb weld at the moment. hopefully that will fix it until i get the new part. if that's not the issue then i'll look into the alda next.

Those bushings have two main parts that fail. The hard rubber on the outside and the plastic ball on the inside. I used some rubber cement and patched mine until I got to the junk yard and found another with issues. I took both apart and managed to cobble together one good one. Then I ordered a couple new spares from Peachparts.

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Codifex
1981 240D ChinaBlue (Got her running with a donor engine.)
1983 300DTurbo w/sunroof.
1984 300TD manual sunroof. (Electrical Gremlins)

Replacing the throttle bushing with a new one fixed the problem and then some. I can't believe how much better it drives now. It must have been partially broken since I bought the car a year ago. Both the rubber ball and the rubber bushing were deteriorated and broken.