My wife's 2000 RX300 FWD [ 55,000 miles ] idles at about 1500-1700 RPM when it's first started when cold. The idle-speed slowly comes down to about 500-600 RPM after about 5 minutes but that seems to be a longer period of time than in the past. It's kept in the garage overnight so the temperature remains pretty constant [ about 60-70 degrees ]. I don't remember it idling that high in the past and it's seems real hard on the engine mounts, transmission, etc. Maybe that's why it needed a new " dogbone " recently. Any ideas? Thanks.

 

Idle speed is governed by input form a host of sensors.

Qualified repair shops can run diagnostics to check which sensor is saying what. Dealers do not mess with with idling any more as that has emission implications. [The good old days to tune + set idle speed are gone].

It is very unlikely that worn mounts have something to do with idling ... the key word being unlikely.

Salim