I have a great 2001 DOHC Taurus SEL with 220,000 miles. It has now developed a rough and surging idle that is most noticable when cold. When it is first started the vacuum will read steady at 5 and it barely runs. If you shut it down and restart it, the vacumm will usually be steady around 10, still running rough. Once warmed up and rerstarted, the vacuum reading is a steady 15 and running fairly decent. I changed the crankshaft position and engine coolant temperature sensor and thought I solved the problem; had vacuum reading of a steady 17 but a day later, same problem. The only codes that appear are 171, 174 and once had a 300. I swapped the following items with my great running 2001 DOHC Sable: throttle body with TPS, mass air flow sensor, camshaft position sensor, DPFE and coil pack. Also changed plugs and wires. There are no breaks or bad vacuum lines. Also changed the PCV. The fuel pressure is always a steady 54 lbs at the rail. I am ready to swap the PCM with the Sable? Any adice?

 

I found the problem. I swapped the entire lower intake manifold/fuel rail and injector assembly from the DOHC Sable to the DOHC Taurus and the Taurus ran great - - even in 0 degree cold weather. So I ended up purchasing 6 new fuel injectors for the Taurus (only $30 a piece since they had 220,000 miles on them) along with an intake manifold gasket set (includes upper and lower intake mainfold rubber seals) for $17 at the autoparts store. However, I really think the culprit was the rubber O ring like gaskets that were on the lower intake manifolds. When I lifted the lower intake manifolds off of the heads, I noticed that the rubber seals were mashed flat with the bottom of the plastic manifold. I think air was allowed to enter at this point when everything was cold and the heat allowed the rubber seals to expand enough to provide a better vacuum seal when the motor warmed up. When I lifted the same from the Sable, the rubber seals protruded from the plastic manifold which indicated they were providing a better seal when bolted to the heads. I guess I will never know now whether my poor idle and surging problem was beacuse of the seals or a few injectors, but I would almost bet it was the seals. Anyway, it is running great with the new seals and injectors- - ready for another 220,000 miles! As a note, it is easy to remove the entire fuel rail, injectors and lower intake manifolds as a complete assembly by removing the 8 long bolts that attaches the assembly to the heads. Be sure to relieve the fuel pressure before disconnecting the fuel line. To remove the injectors once the assembly is on the workbench, remove the four short screws which attach the rail to the manifolds and the injectors simply pull out of each. Lubricate the new injector O rings with oil before assembly. I reassembled the unit on the workbench and then installed the complete assembly back on the car. Also, when the 6 electrical connectors were removed from the injectors, the latch broke off. On reassembly, I simply wrapped a tiewrap around the injector and to the connector. Be careful NOT to drop anything down into the intake ports (like those little pieces of broken off plastic connector latches!)

 

Sounds like what my problem is as well. When I get the funds together will check it out and report back. Thanks for your feedback! I think you saved me a lot of trouble.