Lexus LS400 No Start

94 Lexus LS400
4.0L v8, rwd, 182k miles
Non-TRAC

Bought just a month ago. Ran perfect for 3 days, then lost power. Replaced ignition coils w/new units, ran perfect again for a few days then it started misfiring. High idle (1100rpm), feels like its firing on 7 cylinders.

Cruises nicely at highway speed, but instantly bucks and sputters the moment you press the gas.

Cleaned MAF, IAC, Throttle body, and EGR. All in good shape. Unplugged connectors for each sensor with engine running...each time the CEL came on, then went off after plugging the sensor back in. Did this for MAF, TPS, EGR, and the three emissions sensors by egr.

Engine was still running after all that, so i turned it off.

Now it wont start or even turn over. Found a blown 15A fuse for security system/shift lock & replaced it. Reset the alarm, and still nothing.

Bypassed relay and supplied direct 12v to starter wire under relay. No reply. Now the security system is unresponsive. No alarm, no red light, nothing.

All fuses still good, no trouble codes.

Things i noticed when it ran:
- Drivers side cat converter was about 250 degrees hotter at the rear than the pass. side converter.
- ECU is rebuilt, but done poorly...whoever replaced the caps also fried a couple other circuits. The car still ran fine regardless.

Im about to take her in to the stealership...please help!!

have you jumped the starter relay?

Yes we did, picture below.



Key was in on position. Top right prong had constant 12v like it should. I can hear things clicking and hissing near the intake, but no activity from starter.

Does anyone know if 94 came with an immobilizer? I thought they didnt show up til 97??

if your on the starter relay and jumping the load side of the relay the starter should atleast crank. so you might be looking at a wiring issue to the starter or a bad starter itself

How are your engine grounds? If I remember right- there is one underneath from block to drivers rail that like to rot off. Starters are not a fun job on those. Buried in the V.

Thanks for the diagram!

Where did you get it? And are you sure its for a 94??

UPDATE:

Removed anti theft ecu and inspected circuit board. No leaky caps, but the main bus is toast:

Seems odd, but we also noticed that the AM2 fuse in the main fuse block is a 60 amp fuse when it should be a 30 amp.

I thought AM2 was for ignition only....could this be my no-start gremlin?

Also, replacement theft ecu is out of a 93 sc400. Boards look completely different, but plugs and pinout are identical:





This should work right??