I have a 2002 SC 430 that two years ago suddenly developed an intermittent stall type problem, similar to vapor lock,
which occurred for a fraction of a second, often times repeated over several minutes, then it would be fine. It was an uneasy feeling that the car would stall, but never did.
I took the SC to Lexus and left it to be test driven over several days. The test driver said he experienced it only once and, since it was periodic and not consistent, he had
no idea to the cause or solution. In a conversation with a sports car mechanic, he suggested I try the following: drive the car until the gas tank was near empty then fill it with Shell V-power 92 octane and do this over three fillings. That was two years ago. As long as I’ve used Shell V-power the car has run fine with no problems. In fact, my miles-per-gallon increased. (Note: this is not a commercial for Shell, it is just my experience that solved the problem.)
