i have a miss at high speed. i have a new fuel pump ,and new filters,fuel pressure is right on.(1973 144/B20F,fuel injected)also on the control unit there is a round knob,what does that adjust?seems to run OK for about 20 miles then feel's like it is running out of gas....fuel tank is full....what do you think?

Just to throw the full gamut of 'high speed miss' causes out there - how about a flat cam lobe? At low RPM and power settings the cylinder can breath adequately through the smaller valve opening, but floor it at higher RPMs and suddenly that cylinder can't get a full breath, and will run weaker than the others.

Of course, that's not a problem that would come into play only after 20 miles.

Here's a link with some D-Jet diagnostics. Check the sensors with a multimeter - the coolant temp sensor in particular has a large effect on mixture. The air temp sensor has very little effect.

http://www.icbm.org/erkson/ttt/engine/fuel_injection/d-jet.html

Whenever I get a high speed miss I check the spark plugs.
(They're cheap!)
I use NGK BP6HS
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma

My fuel pump used to seize up a little after running about 20 minutes. I'd shut the ignition off for a second then back on while at speed. It would seem to free it up and be okay for awhile. Had to replace fuel pump.

Whenever I hear "miss under load" I think "weak spark"

How are your points? How is your coil?

c

The knob is the idle mixture adjustment, and has no effect whatsoever on anything else.

When was the last time you replaced the fuel filter?

i checked plugs and they were a little fouled.i also adjusted the points ,seems to run better. how do you adjust to get a lean mixture?

Was the point gap closing down? That would explain a lot; you may not need to adjust anything. Note that when you increase the point gap, you also advance the timing, so recheck that.

The adjustment on the computer box has no effect on plug color while driving the car. If the plugs still tend to foul and you know fuel pressure is correct (right around 28 lbs.), the prime suspect is the water temp sensor, which is the one at the right front of the head right next to the aluminum cylinder with the rubber hoses. Make sure the wires to it make good contact.

Only after you're sure the car is tuned right when driving should you adjust the computer box. Simply turn the knob for the fastest idle speed. If something else is still wrong, though, you'll end up with an incorrect adjustment.

points were real wide.. could be one of the sensors causing plugs to foul . thank you... 1973 144 sedan........

Real wide will do it just as much as barely opening. I once
set my points to be really wide and the car would run okay up
to about 4k and then just stumble. Setting the points to "they
open but not a huge amount" produced a car that ran about correctly.

People say that you need to get the points dead on and you need
to check with a dwell meter. This may be the case but I have
usually just eyeballed it and the car ran well enough for me to
not care about it further. But then I'm just kinda sloppy about
some things...
chris