I have an EF which shutters when it idles. It as always had a small occasional shutter since about 100,000km but it never got worst. It now has 230,000kms and has developed a major shutter/shake as if it was dropping a cylinder. It still Ildes at about 700rpm.
I have replaced the plugs and leads which did not help.
Check the head. Pressure test it, you'll have to buy a device from your auto parts store and plug it into each spark plug hole and start the engine. You'll have to get the correct pressures from a book or the net because I dont know them off by heart. But you'll be able to identify if any valves or seals are broken. Hope this helps. Cheers
Check your Oxygen sensor located at the Exhaust Manifold look down you see it,after 100,00 klm tend to give trouble and injectors tend to block up a bit cheapest way to clean is add injector cleaner+Octaine Booster into petrol tank and fill it up with petrol
Whats the TPS? I have the same idling problem, shuddering idle and sometimes surging. ONly very intermittent though. Head gasket has been replaced, MAF cleaned (which made a big difference to power), plugs an leads replaced, and Ford dealer having trouble tracking down the problem.