2007 Jeep Grand Cherokee • 88,000 miles

Idle undulates during idling and I can feel surges when driving low rpm's. Seems to cause confusion with automatic transmission of what gear should b engaged? Not sure what else I can say. Whats the best recommended spark plug for my vehicle also?
August 5, 2013.

As far as the engine, have you checked for vacuum leaks and the idle air control valve (IAC)? The IAC is responsible for maintaining the engine idle speed. Also, has the check engine light come on?

As far as spark plugs, I recommend you stay with what came with it from the factory, Champion plugs.