2004 Ford Explorer

Engine Performance problem
2004 Ford Explorer 6 cyl Two Wheel Drive Automatic 82000 miles

2004 Ford Explorer V6 4.0L, Everything Started with a Leftside Lifter click and check Engine Light on, I changed Oil to Synthetic and Filter, Added Sea Foam and STP Oil Treatment, 10 days later the clicking went away, then the Rough Idling started and the codes P2198, P0300, P0312, P0306 o2 Rich Bank @ Sensor 1, MisFire Cyl 2 and 6 showed up. Then I Added a Lucas Gas Treatment, Changed Air Filter, cleaned out the EGR Valve Air Intake area, and Changed all the Spark Plugs to Bosch Platinum pre gapped, and the check Check Engine Codes and Light went away but it Still Idling Rough when at a stop or Low Idle position, motor almost stops. Why? Is it a Bad Lifter, Spring, Coil. What do I check for or need to replace next. Any Engine testings available? Please reply @(derby90@yahoo. Com)
September 1, 2010.

Is it just a slight rough idle, or does the engine have a dead miss?

Is like a MisFire, on Low Idle is when the engine vibrates, shakes and almost dies, a a once in a while stall, all these only while the engine is on low idle, at a stop light, parked. Not while driving or high idel.

Sep 2, 2010.
If it is only at an idle, I would say it is either a vacuum leak, idle air control valve, or throttle position sensor. Since it goes away when you give it gas, the idle air control valve is more likely. Has the check engine light ever come on?

This 2004 Explorer V6 came with an Automatic IAC (no IAC Sensor) so the question is out about cleaning or replacing the AIC Valve, The Engine Miss, it has Low Idle at a halt position while running (ex; Parked, at a Red Light, in Traffic) and it even shut off once when I was slowing down at a stop sign. No Check Engine Lights or any other lights comes on. Is just that Engine problem previously mentioned. I do not see any lose or out of place hoses, leaks or funny noises, the only noise is at the rear muffler tail pipe that sounds like is sputtering, missing, gasping, choking something like that sound. Does The Car has Bad Gasoline? Is it electrical? Air? Bad Injector or O2 Sensor?. Thanks for your time.

derby90@yahoo. Com

Sep 3, 2010.
Have you checked for vacuum leaks? Have you checked the catalytic converter to see if it is plugged?