Bob R. 8/17/2010This is often caused by a vacuum leak, especially in older models like yours. Check all the vacuum hoses and replace them if they are cracked. Most importantly, check the rubber "bellows" from the air filter to the air flow meter, and then to the intake manifold. A loose dipstick or oil fill cap can cause this also.
If none of these works, then it can get more tricky, such as the idle control valve, a mixture that is too lean, or a fuel pressure regulator.
Let us know if this helps....