1982 300 CD.
Went and took a look at this car today and it had a problem that I was not familiar with, and I had not found anything about after doing a topic search. It at first appeared that there was a problem with the throttle linkage. I gave it a pretty good going over an couldn’t find anything obviously amiss, from the throttle pedal through the firewall to the STOP lever apparatus, and the vacuum apparatus on top of the valve cover every thing checked out and looked OK. I eventually disconnected the upper ball joint end of the linkage shaft that is connected to the IP. All the other linkage parts that are in sequence prior to the now disconnected joint work freely. When I grasp the vertically oriented rod attached to the IP it can be operated by pushing it downward and the engine increases RPMs. The pressure required to get a response is substantial. There is a piece of linkage that is towards the rear of the IP that operates a light greenish vacuum unit. If I pull up on this second linkage while pushing down on the forward linkage the engine revs. It appears that the connection to the internal IP is a shaft with a seesaw arrangement (regulating lever?) the linkage pushing down increases RPM while at the same time the other end of the seesaw rises and that linkage operates the vacuum unit. This shaft end with the seesaw apparatus with the linkages attached is located between the IP and the head/valve cover.

My question is regarding the IP shaft that is the seesaw pivot point. I have been looking through my 126 CD and found the 617 engine manual I believe this part that is not moving freely is the IP regulating lever. Obviously this shaft should not require so much force to move, is there some common failure mode I should know about? The area does not appear to be rusted externally, it ended up being to late to go get a can of WD40 that I had forgotten, so I couldn’t saturate the area and see if that would make any difference. It will be the first thing I do when I go back! As it was late with fading light and I didn’t disconnect the rear vacuum unit operating linkage to isolate and possibly eliminate that as a cause of this problem. Any advice as to how this aspect of the linkage could cause this problem is valuable.

I’d like to get this throttle problem solved so I can get the car moving around at more than an idle. I need to get it out on the road for a hell ride to find out if any larger problems exist. Cars got 278k and no records but it fired up in an instant cold about 35 degrees today so compression can’t be too bad, blow by was not excessive but there, so I’m optimistic at this point.

If anyone has any advice or opinion as to why this IP shaft would be so hard to move I would very much appreciate the advice and opinions. I plan on trying to free up any external obstructions of binging agents but I was wondering if there should be some internal IP condition I should be aware of and consider. Thanks.


I'll bring my camera when go back!

Good evening Bill, thanks for that info for sure! Very interesting, I was just searching through my library for an exploded diagram of this IP. I had done a pretty thorough search here, but didn’t find any thing remotely like this. This sounds logical I didn’t get a chance to disconnect the vacuum unit but the force required to get movement seemed more than any vacuum operator could muster so I suspected some problem internal to the IP. I was able to move it and then I would have to move it back it had no spring return function the way it is, I think for starters I’ll use some penetrating oil from the outside as best I can and then work the lever back and forth thru its range and see if I can get it to free up some. I wonder how he got the shaft out as it doesn’t seem that there would be enough space between the IP and the engine to remove it in that direction, I’ll have to look closer maybe the regulating lever itself is removable, maybe a nut or bolt hold it on, take that off and pull the shaft thru. Perhaps the IP needs to be removed or rotated? Your right it’s not mine so I’m not going to start my amateur brain surgery on this guys brain that’s what I’ve got my own for! Thanks for the tip on the used IPs that kind of price must beat a rebuild by a good amount. This cars got some body rot and I don’t anticipate that it will ever be much of a restoration project but I thought that if I get it running dependably for not to much money it would make a good backup or a beater for my 17 year old daughter to cut her teeth on, and when and if it died I’d recoup some from any useful parts left. The guy is asking $350 for it so I’ll bring up the “needed IP scenario” and maybe he’ll pay me to take it away! I’ll let you know if I figure anything out and thanks again for the info.