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Ironmike, Ford Technician
Category: Ford
Satisfied Customers: 3385
Experience:  30 years ASE Master tech L1 . Ford master
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Ford Mustang: I have a 2011 Mustang 3.7 V6 manual. I have had

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I have a 2011 Mustang 3.7 V6 manual. I have had it for two years and have about 38000 miles on it. About two months ago it developed a hesitation when I accelerated. It only did it a couple of times, so I thought it might be bad gas. However, it has gotten more frequent since then and now does it ever time I drive the car. It seems worse when the car is cold, but it will do it after it is warmed up as well. It doesn't happen every time I hit the gas. It sounds and feels like the car is bogging down or choking and it looses power. If you let of the gas and hit it again, it will work correctly. I have changed all four O2 sensors, the coil packs, and the spark plugs with no success. There are no check engine lights. Any ideas?


please let me know if you check for trouble codes(even if the check engine light is not on there may be codes) or look at live data with a scanner.

I would start with checking 2 things

I would do a good cleaning on the throttle body and the MAF sensor. I have seen both when dirty or contaminated cause performance issues. Most parts places will sell spray cleaner for both. You can ask the dealer if there are any updates for the PCM, many times there is an update that will cure issues like this. I did check for bulletins and nothing on the 3.7L but a few for the 5.0L

Lets start here

with a difficult issue like this we need to go back and forth to get direction in diagnosis. The more info you give me the better

let me know what you find

good luck

Customer: replied 4 years ago.

OK. I will get some cleaner on the way home from work and clean the MAF and the throttle body. I forgot to mention this before, but it only does it when the vehicle is under load. I can sit in the driveway all day long revving it up and it is fine. It does sound like it idles a little different now than it used to. Anyway, thanks for the ideas. I will try them tonight and see how the car drives. It may be tomorrow before I can verify the findings for you.






let me know how it goes.

what brand spark plugs did you use

you are welcome

Customer: replied 4 years ago.

I used motorcraft spark plugs which I think are really ngk plugs. They are the only ones I can find for the car at this time. I cleaned the MAF sensor with CRC MAF sensor cleaner according to the instructions on the can last night. I haven't cleaned the throttle body yet because I wanted to try one at a time so I could better I.D. the problem. When I cranked it up, it wouldn't idle below 1200 rpm. Its normally close to 700rpm. I revved it up several times and no change. As soon as I pulled out on the road, the motor started running like crap. It had no power and I couldn't get over about 50 mph. It even spit and sputtered some. It started to get a little better after about five miles, but never got really great. This by far is the worst it has acted. The exhaust smells really funny too. Reminds me of a bad air fuel mix. I was thinking maybe the MAF sensor was already going bad and my cleaning it made it even worse. I was thinking maybe I should get another one and that maybe I started troubleshooting at the wrong end of the system. What are you're thoughts?




If after the cleaning it got worse I would suspect the MAF sensor too. I would like to see what the MAF sensor readings are. This is where we really need a scanner that shows live data.


Customer: replied 4 years ago.

A friend at work told me today that he had a scanner. I don't know if it will work or not, but I am going to borrow it and give it a try. Do you know what kind of reading I should be looking for? I was thinking it might read in some type of volts. I ordered a maf sensor as well. I hope to have it tomorrow afternoon. I still want to try the scanner and see what it does though. That way if it works, I could see if there is a difference between the new one and the old one.

we should see MAF reading of 0.17 G/S KOEO(key on engine off) and 3.55 G/S Hot idle
Customer: replied 4 years ago.

Cool. I am off work tomorrow, so I will get his scanner tomorrow morning and see if it works. I will let you know if it works and if it does what the readings are. Thanks again for the help and the knowledge.



you are welcome Chris

If you have a smart phone you can purchase an APP (torque 2) 4.95 for an auto diagnostic program. You need a blue tooth DLC adapter which can be purchased from e-bay for 15$ or less. I use this on my Samsung exhibit and it work great, live data and codes.



Customer: replied 4 years ago.

Hooked up scanner and it worked. Tried it on the old maf sensor. Got 12g/s with key on and 800 to 900 when it was at idle. I put the new maf sensor in and got 0g/s key on and around 370g/s at idle. Car seems to be running better. I am going to drive it some more to make sure.

great, good job
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