hello all,
i have a 1990 5.0, the timing jumps all over the place at idle, with the advance in or out. i just went through the harness and ohm'd every pin location on the wiring harness and never came across anything unusal except the tfi module so i replaced it, needless to say it made absolutely no difference. heres what the car does, idles very rough, sounds like i have a big cam and its stock, when i rev the engine up it shakes and misses up until around 3500 rpm then smooths out, and you can feel the car shake again on decel below around 3000 rpm. i have been trying to figure out this problem for awhile now and am frustrated as hell. please help!
i have an msd 6al, new cap rotor wires and plugs. now a new tfi module. vortech blower, 70mil T.B., 80mil mass air calibrated for 24p injectors, and of course 24 p injectors, and miselanoius other parts. this car ran this way before i put all the performance parts on it and they have just added to the problem.

 

I don't mean to make you feel stupid here, but did you check to see that the distributor is clamped down? If so, then you may a timing set (chain or gear) that has jumped a few teeth.

 

i know it hasnt jumped i had the heads off to replace my head gaskets and the cam was dead nutz with top dead center of the #1 piston(same with the distributor ). and there is absolutely no lag of the timing chain when ive spun the crank by hand, the cam and distributor both move immediatly.

 

And the distributor is clamped down....?

Maybe you have a failed pickup. Is it a magnetic type?

 

And the distributor is clamped down....? yes
Maybe you have a failed pickup. Is it a magnetic type? ...i could have a failed pick up that will be the next thing that i replace. so ill give you the update if that solves the problem or not