My thoughts too! I'd start with the fuel filter, and a fuel injector cleaning(motorvac) can only do good things too-no more than $150...no diy because it is done with a machine. I'd bet that the fuel filter is the culprit. If the car has been fine on regular for 2 years, I'd say that the '87 gas is ok(it'd cause valve pinging rather than no response).
O.k. Thanks for telling me about the fuel injectors. I had no idea they had to be done on a machine. I assume the car is EFI then is the reason? On my Honda Accord, I just have a fuel rail that you pop out the old, put in the new, and your on your way.
I found a fuel filter at O'reilly Auto Parts for around $16.00. AutoZone didn't have one at all, but they did have the directions for where it's located for removal. Sounds easy enough, but I wanted to make sure:
On your 1992 LEXUS LS400, the FUEL FILTER is:
UNDER VEHICLE, DRIVER SIDE, BELOW SEATING AREA,
FRONT OF REAR WHEELWELL, MOUNTED ON CHASSIS IN FUEL
LINE
Is that right? Also, I'm having a hell of a time finding a Chilton's Manual for this pig. Parts stores don't even carry them. any ideas there? Sorry for the hundred questions.
Just a guess
Look under the hood to see if your the overdrive cable is loose.
If it is loose thst might be your problem.