Revs going up and down while idle but settles when I give it a hard rev. Anyone else had this problem? Its a 07 Fabia mark 2 1.2 HTP

When its warm? Or when its cold?

Hi there. It happens when warm

Alright mate.

Hmm theres no reason why a petrol should do that.

Maybe its revving to generate more power the alternator. Is the battery healthy?

Is it when alot of things are on? Headlights, heater, ac etc?

Sorry I should have worded it better. My revs are dropping low and then rising to normal, not going high and then low. It does this until I give it a hard rev and then it settles. My battery is good and at the time I just had headlights on

If you try switching the headlights on again, then the Heater Fan turned up, you may note the revs go higher as the Alternator makes sure the battery is charging.

 

Switch all off other than the engine,

and feel & watch the RPM drop as the alternator does not need to activate to keep the battery charged.

 

If starting from cold, the revs may fluctuate until the engine has coolant at normal operating temperature and the thermostat opens.

Then once a warm car, we still might have the Alternator coming on, (enticed),

then on other cars we have regeneration,

& also the Cooling fan coming on, and again that is the Alternator also increasing the RPM when it starts generating.

 

So, engine and coolant all heated up,

no drain on the battery,

and no radiator or oil cooler fans on,

no regeneration happening,

then maybe a car sits at its lowest set RPM.

Unplug the map sensor, see what happens.

Had a friends car which idle was going up and down, new map sensor cured it.

Was that a MAF sensor, Mass Air Fuel?

Thanks for the suggestions guys. I'll check these today and let you know what I find

Hi guys sorry I haven't got back sooner. I've found that the throttle pedal doesn't quite return all the way sometimes and when this happens the revs fluctuate between about 400 and 900 until I pull back on the pedal. What I don't understand is why the revs drop instead of rise if the pedal is stuck slightly. Any ideas?

Hi did you figure out what was wrong with this I've got same issue same car and year also is it a common issue