My tach jumps when i am crusing it deosn't really matter the speed just at constant speed and my engine also misses i just changed spark plugs, sp wires, rotor and distrib i have an 87 305 tpi. I seems to get worse with the amount of timing advance i have, which is advanced pretty far cause i put a new prom and cal pac in there. plz Help


john

 

anyone?

 

the only thing i could think of is that your prom is bad, even though it is new, or the computer is bad. I had a gm product do the same thing. Although I had to replace the control module. try to retrieve a trouble code from it, and see what it says.

 

I forgot to hook up the plug wire on the # 1 cylinder one day after undoing it to adjust my timing. My car did the same thing you describe, it missed horribly and my tach was all over the place. I seriously thought my engine blew, it was in bad shape at the time, until I figured out the plug wire was just dangleing there. Considering the mods you just did I would double check all of the plug wire connections, both at the engine and at the distributer. If you don't find any shady connections then I would question the new wires themselves.

Good Luck!