This is very normal. The extra drag on the engine caused by the alternator and the a/c causes the engine to slow. The engine speed is most likely then compensated by the e.c.u to a pre-set value, thus causing the revs to rise.
A bad coolant temperature sensor is one thing that could cause an idling speed problem with a Peugeot 406. There could also be a problem with the idle control valve.
you have one or more cylinders not firing causing imbalance. check for spark at each cylinder.
to me that sounds like many tings could be wrong with it lines are dirty, tune up, bad gas, or idle is too low
The condenser fan is more likely to run when the car is idling. So if it NEVER comes on when idling you definitely have a problem. If the condenser is not cooled, then your compressor could get overloaded. It may be a problem with a relay that is preventing the fan from running - or some other issue.
why is my ford sport trac run rough at idling. Being that the check engine light is on, start with having the codes read. Your local auto parts store can help with that at no cost.
A bad relay switch could be the culprit if dash lights remain on after engine starts in a Toyota. Cold weather can also cause these lights to stay on after the engine starts.
either the thermostat or the fan is no good. You would need to locate the thermostat and see if its stuck open or closed!
probably the governor going bad
Could be an exhaust leak close to the engine or a bad catalytic converter. It also could be a bad mass airflow sensor.
Could be your Idle air control valve.
My dashpanel lights stopped working in your Chevy Monte Carlo ss 2001 what could the problem be
There could be several reasons why your car is idling hard when the air is on. There could be something restricting air flow to the motor. A mechanic could diagnosis the problem for you.