My 92 SDV 4.9 has rough idle and sputters after the warms up . When i start the car in the morning it run like a champ ,but soon after it reaches normal temp. range it starts to run like this ,i'm puzzled.Here,s all the new parts i have replaced. Rebuilt 4.9,spark plugs and wires,cap and rotor,(all A/C DELCO ),iat sensor,map sensor,isc motor,thermostat,hoses, vacuum lines,cleaned egr tubes anbd throttle body, air filter,cat converter replaced by previous owner.,fuel filter and i only put BP/AMOCO premium .The egr valve works fine.Now if i run the a/c while crusing no problem until i stop at a red light the feels like it want to die ,then surge forward.I haven't change the o2 sensor but i don't think that the problem ,leaning more towards fuel pump problem.NO codes showing up.car average 15 mpg around town.Asking for help,please.

When you changed out the ISC motor, was the calibration performed by the book? It sounds kind of like it might be mal-adjusted or even not working at all (see related posts that show you how to go into diagnostics mode and observe the operation of the isc motor switch). Could also be a malfunctioning TPS. Just a thought.

It was done by repair shop ,but i don't think it was done right.I can see the plunger working ,so i guess it must be working.Today while driving with the a/c running ,while sitting in traffic,the car started idleling up and down then died .I fired it back up ,it was missing .When i started up at work to drive home no miss ,but sputtering after it got hot.Anyway,thanks for the info. i'll keep you posted.

hey mane. u ever find an answer to ur rough idle and sputtering

Sounds like mine did when the #8 injector failed. Seemed ok cold, but when warmed up ran like do do. #8 failed, then #6, then #4, all in about 2 months.

FSM has a good troubleshooting seq for injectors/plug&wires. Follow it and see. Basically it shuts off each cyl and you monitor for a rpm drop. If you find no drop, there is the suspect cyl.

Tom