Weirdest Non-Starting Problem

[GCPRO]

I could not find this problem reported in another thread. It has been plaguing me for years now. Any ideas would be appreciated.

Problem:

• Car randomly will not start

Vehicle info

• 1990 Supra with 7MGE JDM engine replacement 3 yr ago
• T-top
• Viper alarm

Symptoms

• Not related to humidity, temp, engine temp, etc.
• Flicking key repeatedly sometimes gets it to proceed
• Leaving car unlocked seems to make a difference
• Not using Viper (use old style key in door to lock/unlock) seems to improve things

What’s been tried

• Replaced starter motor 2 times over last couple of years. Another one (Bosch this time) is going in this weekend (not expecting it to make a difference)
• Replaced battery
• Battery power and ground cables replaced
• Ignition switch and tumbler replaced
• Replaced relay supplying V to starter solenoid

My intuition is that the Toyota theft deterrent system is disallowing it to start, although I am not sure how to test/fix this. I got frustrated trying to follow the aftermarket Viper wiring installation and gave up.



Anyone else see such weirdness? Any ideas?