1997 Lexus LS400 Q&A
1997 Lexus LS400 Question: why the engine idles up and down ?
You could have a vacuum leak, or something else that is effecting the air/fuel mixture. There is an idle valve that controls the idle speed, this valve or the circuit that controls it may be having problems. I suggest you have this diagnosed before replacing any more parts though, the idle valve alone is over $500! - lawrenceg