C5 2.0 16v (ew10j4) idle issue

[woolfy981]

Dear All!

I have a c5 with ew10j4 engine and have an idle probleme.

The idle is perfect when the engine temerature is normal. But when the cooler fan or clima or rear window heater switch on, the idle will be very poor and the engine stuck.

I'd replece with new parts:

Map sensor
Idle control valve
Air temerature sensor.

Any idea?

Thanks,

Woolf

[GiveMeABreak]

It sounds initially like an electrical drain / insufficient voltage. Battery / Alternator? If the car starts Ok and you don't suspect the battery is faulty, the Alternator is likely to be the suspect. The alternator supplies the electrical needs for the car once it has started, but if it is not working properly, it won't be able to supply enough power to keep the car running and it will slowly die on you. The battery also won't be getting charged properly and that will cause a battery drain over time.

Putting on the air con and the heated rear window, both of which require a lot of current to operate will cause the vehicle to stall if the alternator is not generating enough current to keep everything running. I would get this checked out before you start changing other components, as this could be a waste and unnecessary. A garage will be able to test the alternator for you - but they do wear out and can be rebuilt / or just get an exchange unit.

[woolfy981]

Thanks for your answere.

Mechanics check tha alternator, and it was work perfectly. He try to unconnect the data cabel between alternator and ECU, but the issue is same. BUT if I unconnect the 2 pin connector from the alternator, the idle is perfect (the battery is not load at this time)

[xantia_v6]

It could be that there is a voltage drop in some circuit that is common to the cooling fan, HRW and some aspect of the engine management. With no involvement of the battery or alternator circuits.

Without a wiring diagram it is difficult to suggest where to measure for voltage drop, but I guess measuring the voltage at the heated rear window might be an easy place to begin.