Originally Posted by 99v6mag
The truck starts and runs!!!! It runs great if you take it easy on the throttle. The problem occurs when you put it to the floor. It starts to backfire. If you hold the clutch in and let off the gas it will stop backfiring and then you can keep on driving.
Well their is somethings that you should try to do if not already been done.
1. Clean the distributor contacts of any corrosion and check the rotor.
2. Check the spark plugs for fouling, if they're fouling then find out what is going on to have them foul. Typical types of foul are carbon and oil foul. Oil foul is a problem. With your truck stick with old fashion copper plugs.
3. Check your timing chain make sure it isn't damaged or the chain has jump - if it jumped then timing is off.
4. Of course being it's a 86 it is not fuel injected so take the carb off and clean it inside and out with carb cleaner and compressed air. Be sure to prime the carb with some gasoline when you put it back on the truck.
MOST IMPORTANT IS HAVE THAT CARB TUNED, Usually a backfire is from having to much fuel. But this again can be lead to improperly connect the wireset. But tune the carb.