Very little low-end power... ideas?

[KevRC4130]

Hey everyone,

So I didn't know my beloved 1984 300D could get any slower... But it has.

It's reallllly sluggish off the line, and struggles to make it up hills. Once it's at speed, it seems fine, and the transmission seems to be working well.

I do live in Southern California, where it's been HOT (100 degrees or so) - the problem seems to be worse in the heat, but that could be all in my head.

Any thoughts? My novice mind is thinking it's something like the o2 sensor, but I really don't know.

Thanks!
Kevin

[Wodnek]

No o2 sensor on these primative diesels. restricted fuel maybe? Try replacing both fuel filters.

[Wodnek]

Also, possibly the bowden cable to the transmission slipped and lost adjustment. That could be causing too quick an upshift. What happens if you shift it manually?

[Strand]

How's your throttle linkage doing? This sounds dumb, but I noticed a dramatic improvement in initial acceleration after a quick lubrication of the easily accessible linkage components. I can only imagine what a thorough cleaning/re-greasing would result in.

[tangofox007]

Cleaned your intake manifold-to-ALDA pressure line lately?

[toomany MBZ]

^ I second this.

[gastropodus]

Have you checked compression on the engine? If not, is it using quite a bit of oil? An engine with worn rings will often run normal in the upper RPM range, but poorly in the low end.

Kurt

[clacker]

Injection pump calibration, not a cheap fix either but the last thing to do in a long line of things to check. It is simply amazing how much power is lost of the years until you have it done!
GO through the entire fuel system-tank screen, filters, test injectors and compression, check boost and vacuum controls, when all else fails go inside the pump.

[Zacharias]

Everything else people have mentioned is fine.

I would add: there is a big throttle pivot bushing up at the firewall, that is connected via a clip to the horizontal part of the throttle linkage that makes the other linkages move.

When this bushing comes apart with age, it means that pushing down on the pedal is giving you about one-third the normal throttle linkage travel, hence way less than normal power and no way to climb a hill or merge into fast traffic.

I have attached a pic of the bushing. Usually the separation is behind the rubber part and it will be hanging out of the firewall opening (you will see a white piece poking out, as in the pic). It is supposed to be flush (second pic).

Also in general, even if this looks okay, have someone sit in the car (motor off of course) and press down slowly on the throttle pedal. You watch under the hood to see if the linkage to the injection pump is moving through its full range of travel. If not, something else is messed up in the linkages.

[scottmcphee]

Maybe someone replaced the go pedal with a slow pedal as a joke when you weren't looking.

[rscurtis]

Have you verified that it's starting in first gear?

[Phillytwotank]

Idea - Low fuel pressure caused by failing lift pump

[oldsinner111]

also check hose the little one on the turbo for leaks.