It really sounds like you have a bad coil. I have seen one vehicle do this. It was a bad coil. <br>When you changed the Distributor cap. How was the ground strap in the distributor?<br>all so, is your distributor loose? if not than your timing is probably ok. unless it has a problem with the timing chain.<br>You can take the truck in to a garage and just have the problem diagnosed. We would normaly charge one hour labor for this. $60.00 <br>PS. I check the coil that was causing the problem just like you have. It passed all the tests I ran on it with a DVOM. only an ignition scope would have shown the problem. low output voltage. Coils are cheap. and easy to install. maybe you should try one.