i've got a 92 7.3na with approx 90k. it idles at approx 500rpm, it runs rough between an idle and smooths out at approx 1k rpm. it's hard to describe how it runs. it kinda shutters or buffets. maybe even surges. the surging or shuttering gets faster as you increase rpm then goes away or becomes unnoticable above 1krpm. at an idle the whole truck kinda twists side to side and if you're runinng down the road/ accelerating between 500 and 1k you can feel it. i don't think it's affecting anything, the truck has plenty of power. there's no smoke associated with it unless i stand on it. it has a new fuel filter and air filer. has anyone noticed this?

 

The specs for hot idle in gear "auto trans" or manual in nuetral is 650 +/-50 try that see what happens... Are you operating at any special altitude above 2000ft.......

 

Same thing happened to me. Rough idle that shakes whole truck, no smoke, smooths out with throttle. I pulled the injector pump out and the shaft came out of the pump in my hand. I ordered a rebuilt from American Diesel Serv. and the motor runs like new. Cost $295.00 Not saying to jump to conclusions but could be your problem.

 

Hey all, FYI- The injectors will also leak at the (not sure of terms) assembly nut and the head assembly mating surfaces and has to effect spray pattern and amount of fuel delivered. The injectors can be disassembled and cleaned to correct this.
rbpems- $295 for a pump is a good deal! All total after doing a seal refurbish on a pump I had $240 into it, (solenoid, face cam, advance plunger, return hose/ seal kit) plus my labor.

 

It is a good price and I'm real happy with the pump. It looks like new and the truck runs better than it ever has. I'm gonna keep checking my fuel milage too.

Tpolley- I checked my compression, fixed all leaks(fuel and oil) and replaced the rubber seals where the fuel line connects to the fuel filter and pump and still had the same problem as you are. I even ran the fuel down to almost nothing and filled up with fresh diesel thinking bad fuel. If everything else is good- fuel, compression, filters, no leaks, and good valvetrain/valve springs, then it is probably injectors or pump. Injectors could be leaking or pump could be wore out or broke like mine was. With a broken pump it still had power and started without to much trouble be shook and had the same problems you discribed.