1992 6.5 missing at cruising speed but only when letting off to maintain speed not under acceleration. Runs fine starts great only just above 2000 rpm when maintaining speed no load. Any suggestions?

 

My guess is a injector/injectors are dirty or going bad do you have white smoke upon start up?

 

Have one that's let's it smoke a little but doesn't smoke after 2/3 mins. I checked by temping the exhaust upon startup. Won't smoke at all even under full throttle or any other time. It just started this after I removed motor to replace freeze plugs till then ran fine.

 

Another thing that slipped my mind is you could be sucking air into the system first place I would check would be the fuel filter manager there is a O-ring in the bottom that goes bad and usually is indicative of fuel under it on the intake it is like a $3 o ring then if that checks out start tracing the fuel lines to the tank.

 

Checked for air in the system nothing in the fuel according to the clear lines I put on everything. Next it will probably be start replacing injectors. So what's the best ones to get I want new bc I've had problems with refurbished ones and are any of them tested before they send them out.

 

I replaced my injectors and IP about 5 years ago got them from Memphis Diesel and have had no regrets whatsoever.