It takes a bit of experimenting to get right, but basically find some sort of metal plug that will fit snugly into the
IAC / ICV pipe that bypasses the throttle body. Make sure that if it somes loose there's no way it can get into the inlet manifold!!
:
Before fitting it, drill a small hole in the middle (try 4mm first.) The idea is you're restricting the maximum amount of air that the
IAC can bypass. After fitting it reset the
ECU by disconnecting the battery (or pull the relevant fuses for the
ECU.)
Then try starting the car. You may find it takes a second try to start it, as the
ECU needs to relearn the new settings for the
IAC. Don't use the accelerator to help it start or the
ECU won't learn the settings!! If you can't get it running after the fourth try, then enlarge the hole using the next largest drill bit (0.5mm steps are good) and try it all again until it will start on the second go without helping using the accelerator.
Once it's started and idling smoothly turn on all the electrics you can think of (headlights on high beam, A/C, heater fan on full etc etc) and see if it can maintain the idle speed. If it can, you've got a good hole size; if the idle drops and it struggles then you need a bigger hole.
You'll need to drive it around for a couple of weeks for it to relearn the settings for different temperatures. Providing it starts second try then the
ECU shouldn't have problems again with those same conditions.
Before the mod my Mondeo would accelerate down hill after I'd backed off in fifth gear; and the revs would hang around 2000rpm as I changed gears. :(
It was a lot easier to drive afterwards, and also didn't rev it's ring off when first started cold (ie. would have to help with longterm engine life.)