Lexus Repair: 1990 Lexus LS400 Misfire, lexus ls400, rotor arms

Question
Hi Jason,
Two months ago I brought my 1990 Lexus LS400 to the dealer for repairs. They carried out a service, replaced the air filter, replaced the spark plugs and fitted a new power steering pump. After they returned the car, it developed an intermittent misfire. I have been back and forth to the dealer about eight times trying to get the problem fixed.
They kept handing it back thinking it was OK, and I could drive the car for a week sometimes without experiencing the problem. Then, after first starting the car from cold and driving for a couple of minutes, the misfire occurs again for no obvious reason. One time I could not start the car at all and it was towed in.
The dealer has replaced the plug leads, alternator (presumably damaged by the power steering pump leakage), battery, distributor caps and rotor arms. Also a switch in the ignition was replaced as it was cracked apparently. They reckon they have checked the coils.
I have drawn up a list of things that they need to check, but I was wondering if you have any ideas from a fresh and expert perspective as to what the problem might be, given the repairs that they initially undertook.
Many Thanks,
Steven


Answer
Steven,
   Have you check the fuel pressure? What is your fuel pressure at starting up?  What about the Fuel pump ecu?  Are you getting enough sparks? I would scope the uppper and lower coil. Without looking at the vehicle it would be very hard to diagnost it. I would suggest that you find a competent Lexus tech service your vehicle!
Regards,
JP Importz
Dallas Independent Lexus and Toyota Repair/Service Center