a month ago, my 89 Supra, started to stutter at times on acceleration or not. Plugs and wires are good. After setting in storage about a month, it ran fine. Parked at home, and the next day, it barely run, on about 3 cylinders. Took it to a friend who has a heated garage, but decided to bring home and store until spring. Drive home on about 3 cylinders and parked. Went out today to drive on blocks and put on cover. Ran fine. I'm thinking I have a timing belt, that's jumping around. Any ideas?

Have you looked at the distributor cap? cracks, carbon traces? https://www.google.com/#q=89+Supra+distributor+cap&tbm=shop

probably would not run at all if the timing belt were jumped...is it time to change this belt...perhaps you shoud do that...wires and plugs too~

Thanks for you're response. The turbo does not have a distributor, just an exciter and coils. Timing comes from a cam sensor.

the ignition wires come from the distributor cap or coil packs...you've got to have one or the other....switch the coil packs...they are probably two in one unit....test OHMS to ground on each of them to find the defective coil pack~~

If stored with not much fuel in it will cause condensation to form in the tank. You might just need some fuel treatment to get condensation out of the fuel.

do I place induction pick up on cyl1 or cyl8