1990 lexus LS400 will stall to the point of cutting off. The tack will drop below 1 and the car will die even if the mash the gas pedal to the floor. Removed the fuel pump and ran hot from the battery. Seems to be working fine. Checked electrical connector going to fuel pump and does not seem to be getting any power. Any ideas as to cause.

Harvey N Tawatao

• 3854 Answers
• Posted on Jul 04, 2009

SOURCE: 1993 Lexus Ls400 loss of power at 2500-3000rpm

Check your MAF and MAP sensor. The first 80% of your throttle signal from the TPS works with the O2 sensor to try to keep the air fuel ratio to 14.7 to 1 with the ECM controlling the fuel injector spray time and timing the ignition. After the 80% to WOT the ECM puts the O2 sensor in to an open loop and takes the Reading form the MAF and MAP sensor to run the engine richer so there will not be any Detonation to the engine and burning holes in the valves for running too lean. That is why it always feel like you get a little more when you ease off on the gas peddle from WOT. Recap check the TPS, MAF,and MAP sensor and wires to those sensors, if you can get the car scanned that would be great and you may find out which sensor may have gone bad, the other thing to is the fuel pressure regulator may be going bad and at WOT the pressure may be to high causing it to run to rich causing the loss of power. Good luck and hope this helps. 

SOURCE: 1993 Lexus LS400 acceleration stalls or surges

I HAD THE SAME PROBLEM WITH MY CAR. 93 LS 400. THAT WOULD BE YOUR FUEL FILTER OR THE FUEL PUMP GOING BAD. TRY CHANGING THE FILTER FIRST. THE DEALER TRIED TO CHARGE ME $980 TO CHANGE FUEL PUMP.

SOURCE: Replace/fix starter on 1991 Lexus LS400

Not too bad. Not much room, just enough to drop the starter. It is probably easier to go up through exhaust if you can get your exhaust shield off the manifold .

SOURCE: need a wiring diagram for 1990 lexus LS400

My sincere apologies for the delayed response.
I am personally going back to answer your unanswered questions.
I have only been a free contributor to this site for the past 4-months.

I do not know if you still need this information, but I am going ahead and answering it anyway.

WIRING DIAGRAM:
For the 4.0L DOHC 8-Cylinder:
Cylinders:
(back of engine)
8.........7
6.........5
4.........3
2.........1
(front of engine)
Ignition Connections:
............(back)
|.o.o.o.o.o|..|.o.o.o.o.o|
|.^.^.^.^.^|..|.^.^.^.^.^|
|.2.8.C.3.5.|..|.4.6.C.7.1.|
.......O................O
.......I..................I
.......L.................L
............(front)

Again my apologies...
Let me know if this helped, or if you have any additional information or questions. Feel Free to contact me at FixYa.com!

SOURCE: how do i change my spark plugs on my lexus ls400

there located on top of engine under the cover thats says V8 FOUR CAM 32, 4 S.P. on each side,remove both covers and its easy access after that.