Poor Throttle Response below 2000RPM
 

New to the car this '83 300 SD has a "new" motor - I still have to track down the PO to find out how many miles it has....

Here's what's going on so far: Take off from a stop is sluggish, until the revs get up to 2000 or so then things start moving. Feels like turbo lag, but excessive. The car has power when revved from 2200-up through range, but below that it is scary slow, like am I stepping on the correct pedal? :eek: slow. Normal????

:confused:Could this be:
A- poor injector performance (ie not as noticeable at higher RPM)
B- sloppy throttle linkage (I did test this and though there is slop - flooring it from a standstill does nothing)
C- Turbo itself needs service???? (wastegate jammed?)
D- Transmission issue? Not starting in lowest gear.... (I am a neophyte with auto transmissions)
E- Air flow impeded by something...a flap I read about....

Any other wisdom here would be greatly appreciated. :D

By the way does any one use Seafoam in the tank to clean injectors ???
I use it in my Toyota Diesel, but it has new injector nozzles.....and it's a manual.

Very interested in hearing more seem to have the same problem?
 

Hi not trying to thread hi jack but am a new owner as of a few weeks ago to a 82 300sd and have similar symptoms with mine. Runs great at higher speeds can't comment on the RPM's as mine needs a amplifier, very impressed with the way it cruises but very slow at accelerating from a stand still. Any ideas that may give us something to try to help correctly diagnose or correct this condition and boost the low end power?? I adjusted valves and did the diesel purge both of which have made a difference. I have now bypassed my black vacuum box on the valve cover and the EGR. Any suggestion would be greatly appreciated.

Thanks for the response
 

I do have another question. My car after having sat for a while/ or each morning is not hard starting but does require me to cycle the key several times also push on the fuel peddle a few times to get it started, is this normal with these or should I not have to touch the pedal to get it to fire up and idle? It seems as if the fuel is bleeding out of the injector lines? Is there a external valve that keeps the lines full of diesel or is that only done through the injection pump?

Are you using Your Glow Plugs?
If you are is your Glow Plug Light coming on?

Mine was deadly slow (same sympotoms) also due to extremely sloppy linkage between the Fire Wall on down to the Throttle Arm on the Fuel Injection Pump.

With the Engine Cold and not runing; grab a hold of the Throttle Lever on the side of the Fuel Injection Pump. Have someone slowly step on the Accelerator Pedal and see if there is alot of play/slop in your linkage.
Also keep a special eye on the Bell Crank Mounted on the Fire Wall. There is a plastic Bushing (Ball) behind it that falls apart and also the Rubber on them cracks.

For starting it might help to be sure you Idle Speed is within specs. The speed is written on the Emission Sticker along with the Valve Adjustment specs.

I am using the glow plugs, the light does come on but only for a moment/1 sec maybe 2 it is quite warm out though close to 100* so my thinking was it was due to the fuel bleeding down maybe? My linkage feels pretty tight I will double check as you stated and also check the idle specs as well. Thanks for the reply.

At 100 Degrees F the Glow Plug Light would not stay on long.
However, even after the light goes off if you leave the Key in the Pre-Glow positon the Glow Plug Relay will continue to keep the Glow Plugs on for about 20 seconds more. You will here the Glow Plug Relay click off about that time.

If Glowing longer improves your starting you could well have some other wear issue going on.

It is best to give the Milage on your Engine so we would have a better idea.
Also you have not mentioned if when you get your car started there is any smoke or the Color. And, if the smoke changes color or dissapears after the Enigne is fully warmed up.
Does it smoke under normal driving or on heavy acceleration?

If you believe that the Fuel is leaking back to the Fuel Tank While the Car sits the cause is most often an Air Leak on the suction side of the Fuel Supply Pump that is on the Side of the Fuel Injection Pump.
The main suspects are the two pieces of 5/16 inch (7.5mm) Fue Inlet hoses; a few dollars to replace from any regular Auto Parts Store.
Next if you still have the Old Style shiny Aluminum Bodied Hand Primer with age they are prone to be a source of Air leaks.
Replacing it with a newer style Bosch (only get the Bosch made one as some of the copies have had quality control problems) does not cost too much.

Also you never said if you are only using Diesel Fuel or an alternative Fuel.

One question that came to mind when you mentioned the glow plugs still glowing after the dash light goes out. Am I supposed to be waiting until I hear the click of the relay or only watching the light until I crank engine like on newer diesels? The mileage is about 270k the car does smoke at start up after it has sat for awhile I believe the smoke is usually darker/black. If I start shortly after it has been driven recently it starts fine and no smoke also after warming up no smoke while driving, sometimes smokes under heavy acceleration with an incline not usually though, seems to run fairly clean for a diesel and has alot of top end power with good acceleration. I run it on diesel only. I also replaced the old style primer pump because it was leaking big time when trying to prime the system after changing the fuel filters. Thanks for the replies gives me more options to try and things to think about.

ForcedInduction, thanks for the feedback.
82Benzo - don't sweat the Highjack - more questions= more knowledge.

I recently found out that the "new" engine was a pulled from a donor vehicle and installed in mine complete with transmission. It has less than 250K, but exact mileage is unconfirmed.
Here's what I did last night (after replacing the rear shocks):
-Checked ALDA - it is virgin, so I chose not to tamper.
-Checked Vac. lines to Switchover Valve for Overload Protection, cleaned banjo bolt at intake (Coleman fuel worked great), replaced line it was poorly fitted to the banjo and made refitting near impossible due to hardness.
-Removed Switchover Valve for Overload Protection - cleaned by applying light vacuum to all ports.
-Replaced vac line from Vac control valve on Injection Pump, it was cracked and porous, and removed green vacuum dashpot tapped it on hard surface to dislodge particles and put it back in line.
-Checked and clean Vac line and Banjo from ALDA to Switchover Valve for Overload Protection.
-Lubed Throttle Linkage, Pivots, and Braden Cable using a Teflon Based Bike Chain Lube/cleaner - (T-9 Boeshield).
-Checked Transmission Modulator - seemed intact, good connection to vac line.
-Checked Shift Levers in black Vac Box atop Valve Cover - though worn they were not dysfunctional - applied small amount of lube to surfaces to facilitate movement. (earmarked this part for replacement).

Findings: Until warm, car behaved as before. After 10 min at highway speeds, throttle response improved. Shifting smoothed somewhat as well. Most noticeable was take off from an on ramp-using kickdown the car revved and accelerated in a way I had not ever felt - that is to say it actually accelerated :D A nice puff of black smoke out the exhaust and I was on my way.(normally I get no smoke at all when driving).

Further city driving - stop and go - yielded better response to throttle. Kickdowns happened more easily and shifting remained smoother through the gears.

Next project= go through throttle adjustment protocol - all 24pages of it, and consider fuel injection system tune up.