sha4000

I don't know if it would change anything but I would def get the proper battery for the car. A weak battery can cause havoc in these cars sometimes.

Things do happen coincidentally sometimes. Why not just purchase a used cam sensor and see what happens.

Glad it worked out.

Good for you nice car.

Glad you got it fixed.

I suggest that you put some dye in there to find the leak. AC issues can get very expensive don't keep guessing on this one.

Sorry to hear about the tach.

Great, let us know how it goes.

This is a good read.

Have you tried changing the IACV and making sure you have no vacuum leaks?

It's worth a try and cheap enough to do if you know how to solder. Let us know what happens.

The caps in your ecu might be bad and the junkyard one could also be bad. This seems to be a common issue with the early 400s as they age. Check this thread out and determine if this is the road you want to go down. https://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000/656360-all-my-crazy-lexus-issues-solved-ecu-leaking-capacitor.html

Definitely interference.

Maybe your using a valet key which does not start the car. Can you post a pic?

I doubt many cars have the updated ECU If you do try a junkyard make sure the part numbers match up.