I have a 2005 Ford Taurus. It has 30,000 miles and it has an extended crank only in the morning. I bought the car with 20,000 miles and it has always run this way. It also idles rough when in park or at a stop light. The idle varies on the tachometer by 75 rpm and you can hear the engine change speeds.
When I took it to the dealer the first time they told me they reprogrammed the power control module and the problem was fixed; however, it wasn't. I took the car back and this time they told me that it was a flex fuel vehicle and this was common with a flex fuel car.
I was not aware that it was flex fuel and after some investigation (checking the VIN) found that it wasn't one. They also told me that it was common for a car to change idle by 75 rpm. Is this true?
Let's confirm the flex fuel ID. The '05 Taurus came with one of three versions of the 3.0-liter V6 engine. Look at the eighth digit of the vehicle identification number, located behind the windshield in the lower left-hand corner. There will be a letter "U", indicating the standard 3.0-liter V6; the letter "S", for the dual overhead cam version, or the number "2", meaning you do have the flex fuel option on the standard engine.
Flex fuel means you can run the engine on regular gas or E85, an 85% Ethanol/15% gasoline mix. Modifications to flex fuel engines include fuel system components that can deal with the corrosive properties of an alcohol-based fuel, bigger fuel injectors and a sensor that tells the powertrain control module the ratio of Ethanol to gas.
And there is a technical service bulletin, TSB 05-11-13, which applies to both the "U" and "2" VIN code engines, involving the reprogramming of the powertrain control module to correct the symptoms you've described, and a few more.
You may want to confirm that the reprogramming was performed. Slight variations in engine speed at idle can be considered normal on certain engines, but 75 rpm seems high, and the engine shouldn't be surging up and down. Have the service department recheck everything, especially fuel pressure if the hard start in the morning is a consistent problem. Also, vacuum leaks, an EGR valve hanging up and Idle Air Control valve related issues are notorious for impairing idle speed and quality.