The 2000-2001 Foci were plagued with a number of pattern failures. The ones you will encounter are:
1. Old style ignition lock cylinder failure. This one is only a matter of time. Replace it with new style BEFORE it seizes up and requires drilling.
2. PCV hose collapse at intake manifold. Replace with improved part #XS4Z-6N664-BA
3. Alternator pigtail failure. Solder Motorcraft P/N WPT-118 pigtail kit (1U2Z-14S411-TA) onto wiring harness
4. Front spring failure in the rust states usually near the top. Unfortunately you are over the 10yr extended warranty program on this.
5. Rear spring failure in the rust states usually near the bottom.
6. Rear wheel bearing failure. If you have rear disk brakes, this also requires replacement of the rear spindles. There was a program on this years ago. It's over now.
7. Fuel pump failure. The program on this is now over.
8. Front sway-bar end-link failure - Just replace every 5 years anyhow, they're not hard to replace or expensive.
9. Front passenger-side windshield cowling failure causing water leakage onto front passenger floor pan. Clean windshield and replace cowling.
10. Valve-cover gasket failure causing hot engine oil to leak onto the thermostat housing o-ring in turn causing that to fail. Replace VC gasket with the higher-quality Fel-Pro item.
11. DPFE sensor failure causing DTC P0401 to be set. Replace DPFE sensor with improved-design OEM unit.
12. The usual heat-shield falling off problems, again in the rust states.
13. Ignition coil primary-side pigtail failure
14. IAC valve failure causing hard warm starts.
15. Battery wiring seems to need more than the usual attention to tightness and cleanliness, particularly the grounds.
16. Passenger-side engine mount - fluid leaks out and causes excessive vibration at idle. Replace only with OEM unit.
I've worked my way through these issues over 12 years and my 2001 ZTS is now fairly reliable and fun to drive. It helps A LOT if you don't live in the rust-belt states. By the 2002 MY, Ford had many of these issues worked out.
2001 Amazon Green ZTS 100,000mis
2012 Sterling Grey SE Sedan M/T!