98 LS400 Will Turnover, Won't Start no CEL
 

I have a 1998 LS400 w/ 229,000 miles. I purchased the car 20 months ago and have had absolutely no problems or CELs up until two weeks ago. I was driving my car home from work and got a Tail lamp Failure warning light, so at a stop sign I turned the car off. When I tried to restart the car it would turnover but not start. I put the car in neutral and pushed it out of the way, when I got back in it started right up. I drove the car to and from work for three more days without any other problems. The CEL never came on. I did in fact have a Tail lamp out, which I replaced. I then went on vacation for a week, when I got back I started my car, backed it out of the garage to unload our other vehicle from vacation, and started it to move it back in. The next day I went out and started the car, but it died before I ever moved the gear shifter, and has not started since. My first test was to move the gear shifter to neutral and back to park, but that yielded no result. Since then I have un-hooked the battery overnight to reset the ECU, cleaned the throttle body, idle air port, and mass air flow sensor, and charged and tested my battery (battery reads 12.7v before start, drops to 10.4 while turning over, comes back to 12.4+v after attempted start). I have been able to get the car to start a few times if I push the throttle while turning the key, but it quickly dies. I have scanned for codes several times and still am not registering any (I even checked the scanner on a car w/ a CEL to make sure it still worked). The car still turns over, but no luck starting. A few other symptoms include a load humming/buzzing noise coming from the front of the engine (possibly throttle body) after an attempted start if the key is left in on position.

TL;DR 98 LS 229,000 mi turns over, but won't start. No CEL. Cleaned TB, IAP, and MAF. Charge and tested battery.

maybe fuel pump

Would it start with the throttle body open if it was the fuel pump though?

clean the idle ports in the throttle body, probably isn't the issue but definitely won't hurt.

I have already cleaned the MAF, TB, and Idle Air Ports.

I'm sure you know this but I'll say it anyway. A car needs 3 things to run properly. Fuel, air, and spark. Looks like you have tended to all but the spark. While you say that if you give more fuel that it will start makes me think that its not spark. Maybe insufficient spark.
Good ole leaking ECU capacitors could have possibly slimed their way into your life.
https://www.clublexus.com/forums/ls4...capacitor.html
Is the humming, buzzing noise coming from the engine bay or from the dash? Capacitors can be quite noisy when go bad. Kinda like steam in a kettle.

cap problems are rare in 98-00 cars.

is the security light on the dash blinking or on at all qhen you try to start the car? kinda sounds like the immobilizer's killing it.

The humming/buzzing is coming from the very front of the end, I would almost guarantee from the motor attached to the right/driver side of the throttle body.

The dash light is blinking when ever the key is not in the ignition, however as soon as the key is put into the ignition, the security light goes off. I have tried all three keys and the security light goes off for all three.

https://i.imgur.com/N20Rwdfl.jpg

This is the part that is buzzing. Does anyone know what this is? If it can be repaired/cleaned? Or what the price and part number are for a new one.

that's the throttle motor. sounds like it's toast, which is pretty rare. If the wires to it are all in good shape and fully clipped in then it's probably bad. It's not really end-user serviceable.

I would just try to find a '98-99 (2000 is different iirc) throttle body from a wrecking yard.

throttle motor doesn't explain the large voltage drop when starting is attempted, you have either a short or something locked up, such as a starter

Give it some gas
 

Battery is normal; a 2v drop during starter load is fine. Try shooting a one-second spray of starting fluid behind the throttle butterflly, then slightly press on the accelerator pedal while you crank. If it starts and runs for a few seconds, but then stalls, I suspect either an injector or fuel pressure problem. Could be fuel pump/relay problem. First make sure you don't have a clogged fuel filter, but that usually starts showing up when the engine is under load for several seconds. Injectors are ECU controlled, but eliminate the fuel delivery as a possible issue first.

Purchased a used (130,000 mi) throttle body assembly off of '99 GS400 ($275) and replaced my entire TBA last night. Car started up on first attempt. I talked w/ a local Toyota Dealer Mechanic and he said that it is common for the clutch to go out on the Throttle Motor (the part circled in red in the picture above) on the older V8 Tundra's and Tacoma's. Hopefully things will return to their problem free selves. Never got a CEL through the entire process. On a side not fixmiester is correct, a battery will drop about 3v when trying to start, but will jump back up to about 14v after start, during idle. a 2-3v drop while the starter is being engaged is completely normal. Thanks for the help.

TL;DR replaced entire TBA, car started and ran on first try.

not unless it is seriously COLD weather where you are in Missouri (considerably below freezing and not using 0W oil) - I guess I am too used to sunny Alabama! :D