Lumpy idle while AC is on

[Will.]

I was driving around today with the AC on and then every time I came to stop, the idle was very lumpy and the car was vibrating all over the place. I then came to the town, so I put my windows down cool and turned the AC off and the car ran fine. Turned it back on and it went lumpy again.

WTF
:S

 

[Gally]

Iirc is uses energy power while on. I know my car hesitates slightly when accelerating quicker through the gears with the Ac on.

And petrol usage of course.

 

[Will.]

It seems really rough though

 

[r900smp]

Mine is the same.

 

[jinjur]

Me too...

 

[Kane.]

Try using A/C in a 1.2.

 

[Fletcher]

My AC does make a lot of difference to the idle TBH.

I very rarely use AC in the Clio anyway.

 

[MicKPM]

Possibly a fault with the AC demand line to the ECM or even a compressor fault causing the belt run to drag a little more than it should. The system is designed to send a signal to the ECM via a specific line when you press the AC On button that tells the ECM to increase the idle speed to compensate for the request for additional load on the engine. If there's a problem with this the ECM won't know to increase the idle and so cause the slower, jumpy idle condition.

Ideally it needs diagnostics to say for sure if the ECM is seeing the 'request' but it depends on how much of an issue it is for you. If it is a faulty compressor unit it could eventually cause the aux belt run to seize and cause other damage... honestly, I'm an optimistic person but I prefer to plan for the worst and hope for the best when it comes to working on other peoples cars.

Mick

 

[r900smp]

Well hopefully next month JMS will be removing mine

 

[Goodj]

AC will pull power from the engine one way or another.

raise the idle?

 

[Naith]

just pull it out, we did. well fred did we had no choice.

 

[MicKPM]

AC will pull power from the engine one way or another.

raise the idle?

You can't adjust the base idle as it's electronically governed... Remove or repair

 

[Goodj]

You can't adjust the base idle as it's electronically governed... Remove or repair

ah well, worth an ask.

thought it may have been a little more complex than that