I purchased this truck from a "trusted source" few months ago.
During my time in owninh this truck ive had several things that go wrong

1. truck ia running rough idle. The rpm guage likes to move around the 1 nd 1 1/2 area.

2. white spoke accures for two minutes but goes away .

3. today when i accelarate my truck started to stop when letting go of the gas then makes a speaking sound/loose screw sound.

4. power doesnt go out at park but at stop. weird.

 

Have you had to add coolant to the reservoir? The 97 and some of the 98 4.2 V6s had bad lower intake gaskets.What happens is,the gaskets go bad.After the engine is turned off coolant leaks by the bad gasket area into the cylinder/cylinders and fills them with coolant.Upon start up the engine hydrolocks causing catostrophic damage.The 97 also had a recall on the timing cover gasket.Some of the 98s were affected too.

From what you are saying about the white smoke it sounds like your lower intake gaskets are going bad or are already there.If they are you better replace them ASAP!

 

i havent needed to put coolent in the truck. it never over heats and i thought that was the cause of a blown head gasket.

 

Yes,a blown head gasket causes white smoke from the exhaust also.But being it is a 97 I was looking at the lower intake gaskets as being the culprit.If you're not losing coolant then it's not the lowers or the head gasket that is causing your problems.

I would start looking at fuel and tune up related problems.Such as,fuel filter,injectors,throttle body,plugs,wires,coil,etc.