Hi
I'm new here and was hoping someone can help with my engine problem, which is this.
When I start the car it idles at about 1000, then revs up to about 1800, then back down to about 1000 again-then keeps repeating this, with the revs going up and down. Also when in drive I can be doing about 30 mph without touching any pedals, which is a bit alarming!
Hope someone can help,
Thanks
Fritzy

Welcome to the club

Not sure what to say about your problem mate. Have you had the diagnostic error codes read to see if the car is throwing up any errors? When was it last serviced (with a spark plug change)?

Thanks,
Anees

Sounds like you have some sort of air leak, thats why your car not reving right, it keeps searching/correcting coz the mix is not correct, or sensor not working/giving incorrect reading to ecu, so its always trying to correct its self.

What year is your GS300 mate? Maybe worth checking that all of the connections on the inlet (induction) side of the throttle body are secure and leak free and that they are not split. As Anees mentions, getting the fault codes read might give some pointers, depending on the year depends how those codes can be read.

Thanks for the tips guys, I have checked and everything seems secure in there, but i think this may be beyond my capabilities. Can anyone recommend a decent independent mechanic in the Bath/Wiltshire area? Seems my nearest is Lexus Bristol, but they are sure to charge me a Kings ransom and it's a days work just getting the car over there and back!
Thanks again anyway!

It's a 1996 by the way

Vacuum leak... Best way to find them is to use a propane cyl. with valve and rubber hose you can use to go around all the vacuum lines and what not. When it smoothes out you have found your leak.

If it does not smooth at all you are looking at an idle control valve issue.

I would try cleaning the throttle body and idle control valve.

Do you have the air-con on?
If so, you may be low on gas, and the engine is compensating for pressure that isn't there... turn it off and see what happens.

IAC VALVE??? Check it out!