1986 4X4 S10 2.8

Sounds like either a bad sensor, like an 02 sensor, or perhaps a throttle position sensor, or malfunctioning fuel injector. If it is carbureted, you may need a carb rebuild.

OK THANKS, WE HAVE REPLACED ALL THE SENORS IT HAS.PUT NEW FUEL PUMP NEW COMP. NEW TIMEING CHAIN AN GEARS. GOT INJECTORS OUT OF ANOTHER THROTTLE BODY.IT WILL IDLE FOR FIRST 2 MINUTES THEN STARTS RACEING UP AN DOWN. LIKE IT RUNS LOW ON GAS. THEN WHEN IT DOES IT STINKS.DONE WORKED ON CONVERTOR. THEN BLACK SMOKE COMES OUT OF TAIL PIPES.

If the air cleaner is attached, the cold air flap is stuck closed in the horn. Causes: -Bad vacuum line. Replace line. -The rod that goes through the flap can slip out and cause a jam. Fix it. -The heater hose from the manfold to the air cleaner is broken or disconnected. Replace or repair. Other possible causes: Catalytic converter or plugged exhaust. Bad TBI injector. Wiring problem. ECM/Computer. Vaccum leak. Blown head gasket. Squirrels. -I had birds stuff my muffler with plums once. They actually flew under the truck, hopped up and stuffed the plums with pits into a hole in the tail pipe. The plums then rolled down into the muffler and plugged it half up. (Yeah, question was 12 years ago. But you never know...)