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Are there any codes in the PCM? Are there any boost leaks? Is the air filter new? Are the MAP and IAT sensors clean? Is the transmission fluid in the pink of health and at the proper level? When were the engine oil and filter changed? Some of the questions that need to be answered before we can move down the diagnostic path.
I'm new to the SHO and I'm not as mechanically savvy as I should be, but here goes: It's a 2011 SHO. the first week I drove the car all was great. Fast acceleration and take-off. It's gotten sluggish at take off and is idling and starting rough. It seems to be getting worse over time. It feels slower and has less power than my wife's Fusion. The check engine light is not on. I'm not sure if this means that there are no codes? I ordered an inexpensive scanner to check. This should arrive today! The oil had been supposedly changed just before I purchased the car (3 weeks ago) The air filter is OK. I'll pick a new one up. I took out and cleaned the MAP sensors last night and it didn't change the issue. Transmission fluid is at level and is pink. I'm not sure how to check for boost leaks. All hoses seem to be connected as they should. Tonight I'll pull out and clean the IAT sensor.
something interesting: I purchased a OBD reader. It's showing my boost PSI at -8 at idle. When driving it is almost always in the negative and reaches 0 once in a while. Is this a boost leak?
Most of what you said went so far over my head, but I'm trying to follow. With the key on and engine off it's reading 0. When I start the Taurus it goes to about -10. WOT gets me to just about 0. I'm using a wifi reader and OBD Fusion App. I have an appointment with a local garage to have them look at my car to see if they can figure it out tomorrow morning. If they can't, then I'll take it to the local Ford dealership.