Usually a rough idle caused by a vacuum leak, check your hoses and thottle body base gasket. It could also be the idle air control valve.
If it runs right when you first start it, I'm betting fuel system. Start with changing your fuel filter(s). If this improves it then you might be done but you might also have a dirty fuel tank. If it runs good on new filters for a while but reverts to the same symptoms afterward then you have a fouled fuel tank.
If changing the filters makes no difference then your injectors/throttle body/carb. should be serviced next. Aerosol sprays and engine additives do nothing but cost money and gunk up your system.
If the truck doesn't idle right from the jump then it might just need the idle adjustor screw...adjusted.
Fresh tune ups are a Godsend for diagnosing. These suggestions are assuming that you have a good tune up.
Here are the most common causes of idle surge, stalls at stops, slow idle speed, erratic idle speed, rough idle and engine hesitation (and other problems), it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake
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