Originally Posted by
TxGreaseMonkey
Go over the ignition system thoroughly--you are experiencing serious misfires. Replace the spark plugs (Motorcraft only), if they have not been changed in 3 years or 50,000 miles. Coat the porcelain portion of the plugs with dielectric grease and check the gap. If you have the Vulcan engine, you may need to replace the coil and spark plug wires. Part of the problem may be vacuum leaks;e.g., upper intake manifold, PCV elbo hose, and valve cover hoses (front and rear banks). Tauruses are very sensitive to air leaks. I would also replace the IAC Valve (Motorcraft only) and gasket, which may be affecting the idle speed.
Full synthetic ATF has dramatically improved the quality of upshifts and downshifts on Tauruses I've worked on.