Hey guys this a cry for help i really don’t know what to do now. I try starting my ls almost once a day and it never starts (brand new batterie can hear fuel pump and it smells like good ol fuel when i crank it) but every once in a while it will start and i can go around town turn it off at a gas station and it ALWAYS starts back up when the engine is hot... now i’ve tried boosting it unplugging the batterie when im not using it to always have it full charge. Now i’m taking out the ecu to have it checked out but i really don’t think that’s the problem because if it was a bad connection it would just not start ever and when i use it be unpredictable but! It runs great no problem hi revs a-ok. Now i’ve read on some forums that it could be the anti-theft system but even when i lock it from the outside the little red light does not flash (im going to check again at nightfall though). Any ideas i’m thinking no spark but why would It only sometimes (because to be clear it starts once in every say week and a half) and if i don’t touch it for like 2 or three weeks i get in it and it starts no problem. I’m stumped and need some help please guys im on my knees here i want my baby back. Please help...

 

checking the ECU is a great start since it's a known problem!

more:
https://www.clublexus.com/forums/ls-...capacitor.html

 

ECU is a top place to start on these older cars to make sure that is not the problem. The battery cables as well as any connectors in the wiring harness for shorts. If there are any signs of a parasitic drain would be worthwhile to verify too.

 

While the ecm is a suspect and the LS does have a few unique complications that simpler engines don't have, I thought a basic primer might help:

 

Actually there is a parasitic drain so might be some short circuits but it has allways had it so don’t think thats whats preventing it from starting must be the ecu as mentionned earlier but why would it just start sometimes and (most of the time it doesn’t) but sometimes it does start and runs perfectly and after checking the troubleshooting for the ecu none of the the symptoms match i’m thinking no spark

 

If your electronics seem operational and problem persists, seems related to temp/humidity and ambient temperature; check your idle air control valve, and i had an SC which would intermittently not start due to a broken one

edit/disclaimer: I’m not a mechanic, I am just kind of a geek for our old Lexus cars. I have a wealth of nearly useless niche knowledge, most of which is beyond my mechanical ability, workspace or both.. ranging across LS/SC and some of the GS cars