mk1 focus idle bad with elec load or a/c

[steveo3002]

mk1 focus 1600 , idles great with no electrical or air con turned on , soon as a/c is on the idle is up and down and generally too slow

in an effort to fix this i have replaced the vac hose thats common to fail on these , cleaned the tb , and replaced the idle valve , then reset the ecu by disconecting the battery as per the haynes book of lies

any ideas what i can look at ...surley its got some doo dahh that raises the idle to compensate for the extra loads ?

[bortaf]

There's a pressure switch on the A/C lines that ups the idle when it's on (also on on the P/S) check that working? what idle valve did you use, i've found the cheaper ones are very slow to respond to the ECU letting the engine stumble before it stabilises the idle for a second then stumbles again as the idle valve is too slow to react.
The crank PCV pipes split a lot as well, letting too much air in for the idle valve to keep up with when there's a load ?

[steveo3002]

ebay valve..tbh changing it did nothing so I'm guessing the old one is fine

pcv pipe...i think thats the one i fitted , common fail on them apparently?

a/c switch sounds more like it...any idea how i test it??

[steveo3002]

help

[theheap]

Maybe you could test it by metering the signal from the switch when you turn on the aircon.