Mystery Hesitation/Power Loss Problem
 

I have a 1990 LS400 that I have owned since it was new.

This car always runs well when the engine is cold and runs well for the first hour or so.

Then the engine looses all power intermittantly but does not die. The car slows to about 15 MPH even when the accelerator is fully depressed. After about 10 seconds the engine goes back to normal for about another 10 seconds. Then the problem re-occurs continually until I let the car rest overnight.

The engine diagnostic light had been displaying for about 6 months but thethe car ran fine.
After the power problem developed months later, Ichecked the diagnostic code which indicated that the right oxygen sensor was bad. I replaced this oxygen sensor with a new one and cleared the diagnostic memory. The engine diagnostic light no longer recognizes a problem and stays off.

I have changed all spark plugs and the spark plug wires.

I have replaced both coils.

I have removed both ignitor modules for testing but Advance Auto, NAPA, Autozone don't have the connectors to test these modules, although they can test most other cars. I live too far from Lexus or Toyota dealer to make it to them. They want to test the ignitors on the car.

I have checked hoses for vacuum leaks but found nothing.

I replaced the fuel filter and air filter.

I have gone through several tanks of gas so it's not water in the fuel.

Any help on solving this problem is greatly appreciated.

Thanks.

RE: Mystery Hesitation/Power Loss Problem
 

Strangely, I recently bought a '90 LS400 with the exact same problem. Have you found the solution? If so, I could sure use your information. Please reply.
Jerry S.

RE: Mystery Hesitation/Power Loss Problem
 

I have a 92 Lexus LS400 with the same issue. have any of you gotten a solution. I know that lexls.com have some excellent site. Let me know your status.

come to think of it. if it feels like a kick back after you have stopped and you push pedal, it seems like it wants to go, then you have bad transmission solenoids-- #1#2

How did you solve that problem please post it, I have 97 LS400 which is having same problem

Try putting at least 1/2 to 1 cup of B-12 from Autozone or Advance Auto in your Tranny. I did that and it ran wonderful or you can try cleaning out your tranny but do not take the pan off, there is another way.