i have a 95 cherokee laredo, upon startup the tach does not work give it some gas and it jumps up and acts very erratic. while running at speed down the road say 55 mph the tach starts jumping around and seems to cause the transmission to down shift… i have posted here before and someone told me to change rotor and cap i did that and didn't fix my problem… i need help please. also when it heats up the problem seems to go away… please help i need this fixed