engine erratic idle.

Hi,

Just wondering if anybody else in here experienced a rough engine idling mainly at
first start up with the a/c switched on?

I have a 2002 Citroen C3 [auto] and currently having this symptoms.

I've fitted new spark plugs, oil, air & fuel filter but still running rough at idle.

I noticed a bit of hissing noise around the intake manifold area just before the a/c compressor cuts in,
then the same hissing noise disappears once the a/c compressor cuts out.

My immediate thoughts was a vacuum leak but am unable to locate any

There must be a sensor or a switch to advance the engine idle just before the a/c compressor
cuts in, but I haven't got a clue which one or it's location. I'm hopping that maybe somebody in here
had the same issue before and can point me to the right direction.


Cheers guys,
sphynx.

Hi Sphynx

There must be a sensor or a switch to advance the engine idle just before the a/c compressor
cuts in,

The advance of the engine idle is controlled by:

The engine speed sensor (not sure where it is, but my guess is its the crankshaft position sensor (here at ECP) which is 'on the front face of the bell housing')

The Engine ECU and BSI (Battery box and Glove box)

The Engine idle stepper motor (On the throttle body)


So, the 'switch' is the software in the ECU and BSI which powers the idle stepper motor.

Probably its not going to be the ECU/BSI or crankshaft sensor or idle stepper.

Could the problem be due to an overfilled A/C system locking up A/C compressor (has it been refilled recently)?

I've fitted new spark plugs, oil, air & fuel filter but still running rough at idle.

Just leaves the ignition coils.

I don't know what the hissing is, sorry.