Yaris Problem

[janey11]

Hello Everyone.

Ive recently had a problem with my car which started suddenly. When the car is stood still, in neutral handbrake on, the engine continues to rev as if im pressing the accelerator then there is a single knocking noise, this repeats untill the car is in motion again.

Ive taken it to my regular garage but they cant find the problem as it only happens intermittently and suggested i take it to a Toyota dealer to run diagnostics on it.

Obviously this is really expensive but as i drive for a living i will have to do so. I was just wondering if anyone maybe had the same problem or have heard of it before i transffer my wages to the local toyota :(.

Any help would be much appreciated thanks x

[Bos]

I know that if the aircon is switched on when ticking over the revs will rise and fall, but I've never heard of a knocking noise.

[stantheman1]

Is the engine warning light illuminated? If so the code needs to be outputed if not, possible causes for uneven (high and low) rpm at idle could a dirty/faulty MAF(mass air flow)sensor, Idle control valve or throttle position sensor. The most likely been a dirty MAF sensor, these can be cleaned but care must be taken to avoid damaging the sensor. There is a how to somewhere on this forum and when I get a minute I'll try and locate for you.

Btw I'm assuming yours is a petrol and not diesel! Not sure about the knocking, also what mileage has the car done?

[cabcurtains]

How high do the revs go?

If its 200-300 more than normal i would go with Bos and say its the Air Con kicking in.