most of the weird intermittent problems mentioned in this thread sound like a classic case of bad ECU capacitors

you would not believe all of the issues that this one inexpensive fix solved on my car, all the impossible to figure out problems went away at once!

 

this is a great diagnostic thread
https://www.clublexus.com/forums/sho...d.php?t=551125

 

I have had the same problem with my car stumbling and cutting out at idle I have changed out everything from plugs to fuel filters and it still happens only in hot weather. I changed the coils and even the MAS costing 1100.00 at the dealer and when it gets hot the car will do this about couple of months. All I do is open the hood let her cool for a while and off I go. I have 277,000 miles and she still runs perfect still gets 23-24 MPG on the road and everything is still original they sure built one hell of a car. I ran a toyota cressida 529,000 and everything was original lets see a MB do that.

 

I tried two different used ECUs in my 1991 LS400 (Owned for 20 years, 255K miles) but still had the engine cut out problem in hot weather, regardless of engne speed. Then last year I took my original ECU to a company that specializes in ECU repair. I throughly described the symtoms and even gave them pictures from this site of the culprit leaking capacitors. They said mine were not leaking and the unit was meeting specs. The engine still was cutting out, now more frequently.

But replacing the fuel pump seems to have solved the problem.

It has now been 5 months since I replaced the fuel pump and the car continues to run perfectly. Granted it has not been extremely hot outside and I still have no idea why hot weather would affect the fuel pump.

The new pump came with an insulating sleeve which the old one did not have. I assumed it was to make the unit quieter. Maybe it was for temperature?

 

Very sorry for the resurrection of this thread. But since people continue to have similar problems and I may have an answer why its the fuel pump.
I didn't see anything about fuel rail pressure checks in any of these posts. I would bet the pressure was down and that allows a vapor lock to occur, the fuel pumps could
be weak and just not upto snuff, and rather that the relay being replaced why did no one replace the fuel pressure regulator that may even be the main contributor.
Just trying to be helpful. I should get off this pc and work on the car.

 

You've been a MAJOR help with these threads, I haven't gotten any results yet.. and I took mine down the street the other day it cut off about 7 times just in my neighborhood. The ecu is more what I'm leaning towards as well as the fuel pump.. this WAS an auction car after all

 

A simple thing to try is loosen the gas cap and vent the tank. That is if you drive a bit then it starts powering down.

 

I just want everyone to know, do NOT go and buy random parts unless you have that kind of money. Replacing the spark plugs and wires is a good start and should probably be done anyways if you either don't know when it was done last or if it's pretty much due anyways.




Secondly, I've noticed a lot of people going out and buying parts and realizing it's not the problem.




How I fixed mine? I disconnected the coil spark plug wire (at the coil, since all the covers were already installed) and tried to start the engine. Sure enough, it ran exactly the same (I started with the one on the top because it's fairly easy to get to).




Then, while it was running, I plugged the wire back into the coil. No change.




I then shut off the engine, and took the spark plug wire off of drivers side one... The engine would not start at all. Just cranked over (and yes, the passenger side was plugged in). This is an easy and free test for the coils. I replaced the passenger side one since it runs on the driver's side one, and its fixed!

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thank you to everyone who helped troubleshoot my 93 , I got my ECU replaced two months ago and it runs like new !!