well its my dads truck..we just put a 4 inch straight pipe on it tonight and we pushed his number 11 fuel plate full forward and was taking it out for a test drive to see how much his egts drop and his rpm tach starts jumping around and then goes to 0 then he gets in to the throttle again and it will catch back up and keeps doing this i believe it would be a short somewhere but where do i start to look for that kind of problem? where is it that the rpm guage gets its reading from the motor?..this has happend about 2 times within the last month or 2 but it would go away after about 5 mintues now its seems to be pretty consistant

 

The sensor is mounted just above the crankshaft damper. More than likely the ground has some corrosion and just needs to be cleaned. The clearance is .050 with a non-magnetic feeler gauge.

 

alright thanks ill go check that out...hopefully thats all it is because its starting to get really annoying now.

 

well washed all the grease off the front of the motor and on the balanceer and it seeems to be working good again thanks for the help