Unregular Rpm

[flinston]

Hi guys! In my c4 2007 1.6 petrol there are some unregular readings from obd reader. Rpm jumps 730-780 , thorttle position is 20 and jumps to 20.29 and at last timming reading jumping all the time between 2-6. I can feel little shakes in car. First thought throttle is dirty. I have cleaned throttle using spray . I was afraid to take whole unit out because I read that it needs to be calibrated after. After cleaning still the same. Does anyone know what could be wrong or what more need to be checked to spot problem?

[paul.h]

Welcome to the forum.

 

There is a Haynes manual for the C4 which is worth getting.http://www.amazon.co.uk/dp/0857335766/ref=sr_1_1?s=books&ie=UTF8&qid=1431214312&sr=1-1&keywords=haynes+c4

 

The idle rpm will not stay fixed since it will be constantly changing/adjusting from the management system. However, it you wish to check a few things, in the Haynes manual for engine idles erratically it gives:

- vacuum leak at the throttle housing/intake manifold

- worn or faulty or incorrectly gapped spark plugs

- engine management system fault (have a look on your code reader at the inlet lambda sensor readings, it should switch frequently)

- uneven or low engine cylinder compressions

- camshaft lobes worn

- timing belt incorrectly fitted

- disconnected, leaking or perished crankcase ventilation hoses

 

To this I would check the air fliter is clean and that the fuel filter is not due for replacement.