Engine RPM dropped

[noy_bimmer]

Please help,I have this problem,When the engine is idling with aircon off, RPM is fine.When aircon is on, the RPM dropped and back to idle again.If the aircon is continously on, the RPM drop keep repeating.The car feel very uncomfortable as it will vibrate repeatedly.Is it because of the compressor size?Or pulley size?pls help. Thank you."Once a bimmer, a bimmer forever"

 

[skar19]

isnt it normal for engine rpm to drop when aircon is on. ie there is more load on the engine?

 

[manjit]

By normal mean it shud pick up when aircond is on, then back to idle.....pelik memang pelik.

 

[kevster30]

Noy,

The problem that you are facing is caused by one of these two things:

1) Faulty Idle Control Valve
2) Deteriorated vacumm hoses

When your air-cond compressor engages, the ECU(DME) will sense the load and send a signal to the ICV to compensate. On older BMWs, this function is mechanical and fucntions on the cahnge in vacumm pressure.

All BMW engines need to be air tight and are not tolerant of air leaks. Vacumm hoses harden and crack over time, especially in our wonderfully hot weather.

Hope this helps.

 

[noy_bimmer]

Thanks all.

To make things clearer,
1. When aircon is on, if you notice(you should) compressor is on and off alternately. this is to control the temperature, so that not very cold.

During the compressor on, the RPM will drop, back to idle, and drop again when the compressor is on during next cycle. (do I make things more complicated?)

The car will vibrate and fill very uncomfortable.

I will check ICV and vacuum hose.

"Once a bimmer, a bimmer forever"

 

[MeanStreak]

Originally posted by noy_bimmer@Oct 6 2005, 05:07 PM
Thanks all.

To make things clearer,
1. When aircon is on, if you notice(you should) compressor is on and off alternately. this is to control the temperature, so that not very cold.

During the compressor on, the RPM will drop, back to idle, and drop again when the compressor is on during next cycle. (do I make things more complicated?)

The car will vibrate and fill very uncomfortable.

I will check ICV and vacuum hose.

"Once a bimmer, a bimmer forever"

Noy,
Kevster is right. Check your ICV first followed by the hoses.