My 99 Ranger has a habit of shutting down after it has been ideling for a few minuets. It starts back up easy enough but it’s bothersome when you are waiting in line for something like a train passing. The weather makes no difference. I have run injector cleaner thru it, tried different obtain gas and have cleaned the throttle body to no avail. I have changed the air filter and raised the idle speed. The idle speed increases like it’s supposed to when the engine is started cold and when the AC compressor kicks in. Dont have much hair left trying to figure this out. PS The motor runs smooth and gets good gas mileage. Any ideas would be great.

 

Aging (weakening) fuel pump?
Partially clogged fuel filter?
Extremely clogged air filter?
Dirty (inaccurate) MAF sensor?
Bad CTS (coolant temp sensor) confusing the 'main brain'?
Vacuum leaks?

 

I would eliminate the first three because they would show up more at higher rpm. I would add Idle Control Valve to the list and may put it in first place.