I have had this car for almost 2 years. Have never had any problems but the battery. One day the emission control light came on so I got my manual out and it said it could be bad gas, so I poored gas treatment in it and drove it thru 3 driving cycles and it went off. Now its coming on all the time. I think I have got the problem solved with the gas, I take the hot cable off the battery, reset the computer and it does fine for 2 or 3 days, then all the sudden the car idles down like its going to die, especially when I come to a red light or stop sign, but doesn't die, idles back up to normal, then after I have gotten to up a normal speed again the light comes back on. I think someone has put something in my gas. I took it to auto zone and they put it on they're machine and it said a sensor was bad, sense it has the FFV engine in it, guess what the sensor cost? $550, I ask the tech at Ford if the car would stop if I didn't replace it, he said no, so I didn't replace it. I did how ever change the Fuel Filter and reset the computer by taking the hot cable off the battery, and it went off and stayed off for months. But now with the engine idling down almost to shutting down, I think i have a real problem. Can anyone help?

I think you have a different problem. If I'm hearing right, you have a Flex Fuel Module that's bad and didn't replace it and now you have a low/loping idle concern. I would definately smack the IAC (it's on the throttlebody) with a screwdriver handle and see if that fixes it. When we do driveablility work at the dealership, we keep a good IAC to plug in and see if tat fixes an idle problem before we even hook up a scan tool.

If the OBD was read, what code # did you get? Also, what or which sensor is bad? I can't figure out from your posting, there are at least a dozen various sensors in that engine, for example, there are four(4) O2 sensors alone.