My 98 felicia 1.3 MPi revs up and down by itself at idle. It revs a little high when driving and when the clutch is disengaged it starts reving up and down by itself. I have spent weeks looking for an air leak with no success. I am now pretty sure it is the "Air inlet temperature and pressure sensor" does anyone know what the resistance value of the thermistor is at ambient temperature? Someone may even know a quick way to check this sensor. I do not want to replace it without knowing for sure that this is definatly at fault as the sensor is nearly 70 quid. I have a haynes manual with wiring diagrams but it does'nt give values of resistance etc. Help please.

Probably the inlet mainfoled gasket - its quite common - had it on my Felicia 1.3 - relatively easy to change

John

My 98 felicia 1.3 MPi revs up and down by itself at idle. It revs a little high when driving and when the clutch is disengaged it starts reving up and down by itself. I have spent weeks looking for an air leak with no success. I am now pretty sure it is the "Air inlet temperature and pressure sensor" does anyone know what the resistance value of the thermistor is at ambient temperature? Someone may even know a quick way to check this sensor. I do not want to replace it without knowing for sure that this is definatly at fault as the sensor is nearly 70 quid. I have a haynes manual with wiring diagrams but it does'nt give values of resistance etc. Help please.

Hi,

This isn't Felicia specific diagnosis but in the past I've found this revving to be down to excess air in the cooling system. What happens is air bubbles get trapped near the coolant temp sensor, causing the fuel injection to momentarily think the engine temp is cold, thus increasing the idle speed.

Try bleeding the cooling system...

Hope this helps!

Matt.

right either air leak on manifold or faulty throttle body or needs re-setting

Which reminds me that my wife's 1.6GLXi had a major problem with the idle revs varying which was cured by resetting the throttle body.