Why wont engine run smooth at idle or low rpms ?

SOURCE: ford f350 6.0L Turbo runs rough

Still sounds like there is a fuel issue. I would check the obvious. Check the Air filter and fuel filter and water seperator. Debris could have gotten into the new injector, which also could have upset the other injector. Get the exact code from the dealer your truck experianced.

SOURCE: engine vibration at lower rpms

Check motor mounds.or perform full tune up.

SOURCE: lite tapping in engine,very ruff idle,stops when idled up and runs smooth

ruff idle may b idle controll senc. ----tapping may be plugs-- wires, and or gas try 91 oct gas next 3 tanks and see thats the cheeepset place to start

SOURCE: 1991 F-250. feul injected 460 w/c6 tranny. acts

Hello. katienjoe. the fuel line from the filter to the fuel rail has a restrictor in the line its at the fitting at the rail. the opening messures 3/16 of a inch. so loaded it doesn't pull above 50 mph. you can change the line I did on mine the hot rod shops can supply what you need.

SOURCE: ruff idle on my 2001 for taurus. At higher rpms it runs fine.

It is most likely you wheel alignment (costs about 20 bucks to have your wheels aligned) or try checking the tire Pressure to make sure they're all even maybe hope this helps