1984 300TD acceleration issues different than others posts
 

Hello. Ok so the car is in park. I step on the gas, the car revs up and then without removing or moving my foot it goes right back down to idle... This happens while I still have my foot on the gas. If I step on it again, it'll rev up but eventually it'll come back down. What could be the problem? This happens while I'm driving too. The car has great pick up when I'm on the freeway though.

Digieditny

Have you checked for excessive play in your throttle linkages?

No. I just got this car on saturday and am completely new to mercedes benz and diesels... Is there a tutorial somewhere I can look at?

digi

have someone step on the throttle while you look at the linkage as it moves. odds are good you will see what is wrong if it's linkage related. likely the bolts that hold the swivel parts to the valve cover are loose.
if everything moves smoothly, and it does not look like things are broken, post back.

I'll do this tomorrow morning and get back. Do I do this with the engine running? Link to what the linkage looks like? I'll do a bit of searching.

digi

With the engine off!

Once the helper "floors" it, grab the linkage under the hood and see if you can move it more in the "go" direction.

Super-standard with a new-to-me '80s diesel MB car is to pop ALL the linkage balls loose, clean them, then lube with a drop of ATF (stone age, yes, but MB spec).

After my helper floored it, I was able to pull it in the go direction about half an inch. Would that need adjustment? If so, what exactly do I adjust?

Digi

There is a bunch of info in the Factory Service Manual about adjusting the throttle.

Available here: http://www.classictechlit.mbusa.com/MB/cstmsearch.asp?MYID=1038&SDID=1297&MDID=1168&ENID=1156&catalog_name=Retail

I recommend getting a copy, cheap too.

it could need the coupling on the pedal replaced, or the swivel on the firewall replaced.
take a picture for us.

K I will take a pic in a few minutes.

Full travel at the go pedal should result in full travel of the arm at the other extreme of the linkage the go lever on the injector pump.

Most common throttle linkage failure is the bushing on the firewall:

http://www.peachparts.com/shopforum/diesel-discussion/235493-throttle-pivot-broken.html?highlight=throttle+pivot

Here are some pictures of the linkage. How does everything look? I haven't adjusted anything. I just installed a new primary fuel filter.

Man I never noticed all the rust till I took these photos. OUCH!

digi

Oh I also wanted to say that after installing the new fuel filter, the car felt peppier but it still didn't hold power. Pushed the pedal and the rpms go up but then eventually back down without moving my foot. The car idles kinda rough. Thought it was gonna shut down on me

digi

Does the engine behave the same way if instead of pushing the accelerator, you grab the linkage near the IP and open it up all the way. If it still behaves the same way, you could probably exclude a linkage problem.