Lexus Repair: rough idle when the A/C is on, lexus ls400, poor maintenance

Question
I HAVE LEXUS LS400 1991 WHEN THE A/C IS ON FOR 3HOURS THE CAR WILL IDLE VERY BAD LOSS POWER UNTIL THE A/C IS OFF THEN COOL DOWN IT WILL PICK UP AGAIN NO PROBLEM PLEASE HELP.I BOUGHT THE CAR IN AUG 2003 HAVE NOT REPLACE THE SPARK PLUG OR IGNITION WIRE JUST DO THE OIL CHANGE ONLY, PLEASE HELP.

Answer
Hello, It is important to remember this is a machine. The human can not live on water alone and cars can not live on oil changes alone. Most Lexus problems arise from poor maintenance or inexperienced mechanics working on them. It is hard to say what is going on with it without seeing it but my suggestion is to bring it to a qualified Lexus tech to be looked at.