Volvo: volvo s40 idle problem, compressor clutch, volvo s40

Question
VOLVO S40, 1.6LITERS, YEAR:2002

Sorry for bad English.
Any ideas on this problem.

I have a very difficult problem and to be honest it’s the first time seeing something like that.
The rpm in idling are fine in all conditions cold, warm, ps operation the problem is only with ac on.
The engine is running about 800rpm with ac off. After I switch on the ac the rpm increases to 950-1000 rpm and that’s very normal.
When I pressed the pedal to accelerate the idle valve keep up the rpm near to 2000 rpm and this is continued all the time that the compressor clutch is lock after that every time the ac compressor lock then rpm are increases near to 2000 rpm.

No trouble code stored.
The control valve is working fine after I check with oscilloscope during the problem period it just execute the ecu command. We have an increase to duty cycle.
A/C pressure sensor is new.
Service air condition is done.

Thank you
Costas


Answer
Costas,
I have seen at least one car that the idle was erratic. There were not any fault codes and it turned out to be the Electronic Throttle housing and a download of new information. The best thing at this point is getting the dealer to look at it. Some vehicles are still covered under the emission warranty.