LS Focus rough idle poor economy

[auc-05l]

Hi all,

I have a 2006 ford focus LS zetec automatic.

has been a problem child since we got it 3 months ago. I recently replaced the PCV valve and hose (hose had a massive split). This helped it idle lower round 800rpm, but now it stalls when using the aircon while stationary! the idles is unsteady and the fuel economy is also still rubbish 14L+ / 100kms.

when driving its fine but pulling up to a stop the rpm drop to about 400rpm before bouncing back up. if the aircon is on the engine really struggles to maintain a steady rpm.

any ideas what might be happening. i had one of these 8 years ago and it was awesome! this one has issues..... which are proving difficult to solve. There are no codes when i scan it. the car has 170k kms

any help is greatly appreciated