I just went through the exact same problem with my 91 tracker. 385000kms and she finally stopped running. At first I thought the turbo caused it. Then I thought it was a bad ground. Then I started reading on the different zuki forums. I found that the Computer in these things has a life span of about 10 years give or take a few.
I don't know if you're electronically knowledgable or not, but I'm on a roll; here I go:
They used electrolytic capacitors that over time begin to leak out the electrolyte. The electrolyte is acidic and burns out the tracing underneath it.
My electronic background is limited to a highschool basic electronics course, and some good old tinkering to see what stuff looks like on the inside. So I know what these capacitors look like. Little blue (or black) (usually) cylinders with two leads coming out the bottom.
So I switched the two caps out for new ones (60 cents each) and made a little jumper where the tracing was damaged under the offending capacitor.
Turn the Key........Yeah! It's alive!
And thats my story.
PS. The computer is in the steel box up under the dash, not the black plastic one on the fire wall.
