Twitchy ignition?
 

So my '85 Z31 n/a has been acting strange recently when I try to start it.

First off when it does start it's a very weak start. There's times where it's turning over the motor but wont start. and there's time where nothing happens at all but a click.

I've checked the fusable links they look fine. I got the battery/starter test done at autozone which came back as a positive.

It's really strange because it's intermittent, I almost want to say it's a bad ground somewhere, or maybe it's the ignition switch going bad? With the weather getting colder I'm worried it wont start at all once it gets down to freezing.

Any insight?

I would say this is a classic example of corroded battery leads. I'd replace both the positive and ground straps to the battery.

Get your battery load tested. Be sure you have clean, tight corrosion free terminals on both ends of your battery cables. Be sure the ground (negative) cable goes to a bolt into the frame before going to the starter. grounding through the starter is not a reliable connection. Z's don't like low voltage. causes the electronics to act funny. it is possible to have enough amps to crank but not enough voltage to run the electronics. If you have one size fit all cheapo clamp on terminals they are a problem waiting to happen.

Clean the connectors for the maf or afm, ecu and tps. Deoxit by CAIG is probably the best connector cleaner on the market. spray with CorrosionX after cleaning and before putting together this will help prevent any further corrosion.

if you do the above you may solve your problem but if not then at least you will have eliminated bout 75% of the usual z31 problems. Get an interstate battery. they don't die and they last far beyond the five year warranty mark.

Thanks! This weekend I'm going to be putting a lot of TLC into her, weather permitting. I'll give an update to whether I get it fixed or not.