Expert: Robert Summers - 6/18/2008

Question
1998 chevrolet 1500 - 350 vortec v-8-   my truck has a sparatic miss to it that I cannot figure out. It ususlly misses right after you are under a light to med. engine load.It does not seem to miss at med to hard accel. though.At one time I was blowing fuses for the fuel pump/ecm but that was only for a short time. Now I dont blow fuses but it still misses. Fuel pressure is 55 psi under high vaccum and jumps to 65 psi when vaccum drops.fuel pressure never fluctuates when the vehicle misses.truck seems to miss more when it is first driven and sometimes when it is damp out(but not always). I have changed plugs-cap-rotor-wires-fuel filter-crank sensor-and tested the ign. control mod. I also cleaned grounds and added a 4 gauge aux. ground from block to frame.please help-I am frustrated. thanks jay

Answer
Hi Jay.... check the coil, also take a look at parts you have changed... sometimes new doesn't mean good...if everything is ok check dist for a short to ground in the hall affect reluctor and pick up....is there a lot of miles on the truck...if so check the cam for excessive wear...chasing down an intermittent miss can drive you nuts...hope this helps