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If the plugs, plug wires, are good then suspect a vacuum leak somewhere.
its most likely your idle control sensor. if you replace it the truck should run fine.
check all the Fuses and fuse links (Altnator to Fuse box to battery)
its a vacumn hose issue,,,need to look for a cracked hose at the rear of the motor,,down about half way .
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vacuum leak.
U have a blown head gasket,cracked cylinder head or cracked block.. The white smoke is from water getting into the Exhaust system.
Either the fuel mix is adjusted wrong or the carb is dirty
If the "check engine" light is on, use a code scanner to find out what's wrong. You can borrow, rent or buy a code scanner from most auto parts retailers. Sometimes they'll even show you how to connect it and how to read the results.
If you severely overheated the engine,the cylinder heads or intake manifold may either have warped or blown their gaskets. This creates among other things a vacuum leak which will cause the idle speed motor/solenoid to go crazy.
I've had this problem a couple of times with my 96 Ford Explorer. Either: 1. The car needs a tune up 2. A sensor is out and the car needs a tune up 3. Something is wrong with idle . . . needs to be checked The real answer is that you need to get to a mechanic asap . . . When the idle was loose, the car would die, but when a tune up was needed it ran rough without fully dying . . .
I would check the temperature sensor. Sounds like the sensor is telling the computer wrong information and the the fuel mixture is being affected.