Three problems related to gas recirculation valve (egr valve) have been reported for the 1999 Ford Windstar. The most recently reported issues are listed below.
There is a problem with Ford egines. When it is cold usually a temperature below 20 degrees the intake manifold gaskets don't seal correctly, causing a engine error in the computer. My dealer says over the last 3 years they will fix about 50 a season and already this short season they have fixed about a dozen including my 1999 Ford Windstar.
I bought this car used and from the day I drove it off the lot I have put a few thousand dollars in it. The engine light keeps coming on with codes 171/174 lean on bank 1 and 2 I have replaced the O2, the egr, the differential, I have had the upper intake gasket replaced and the egr hoses cleaned. The light still burns. I have had nothing but trouble with this car since buying it and I will never buy another one. I also had to replace the brakes, the struts and the stablizer bar , as well as one of the tie rods. This van might look great but it runs like crap we have spent enough on this used van to have bought a new one.
Most recent incident - engine stalled with complete loss of power when reducing from highway speed to ~25 mph due to traffic conjestion on north side of chicago after driving ~45 minutes in 95 degree weather with air conditioning operation. Vehicle would not restart. Illinois dot pushed vehicle to shoulder. After total wait ~20 minutes, engine restarted. Drove with air conditioning off and heater on full through remaining congestion (~45 minutes). Drove remaining trip (total of 3. 5 hours) with no futher incident. Prior occurrence on 07/29/02. Similar weather/driving conditions. After 2. 5 hours at highway speed, exited to side road. Vehicle stalled shortly after exit. Restarted after 15 minutes. No repeated incident in remaining 15 minutes of drive. Return trip had no incident. Prior incident in November, 2001. In cool weather, several short errant trips - vehicle stalled. Restarted after several hour wait. Vehicle towed to dealer. No failure codes determined, no diagnosis of reason for engine failure. Dealer replaced alternator under warranty.