tsunami
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I was in a parking lot. I tried to start my Ecoboost convertible. I pressed the brake pedal and hit the start button. The engine immediately began to over-rev. I tried several more times and it still happened. I got out to look at the engine to try to figure out what had occurred. After awhile I got back in and it started normally!
I finally figured out what was going on. When I bought the 2015 convertible, I replaced the OEM floor mats with the most popular 'pan-type' floor mats. To remove the OEM mats, one must pop the mats off of their 'mushroom' plastic pins that extend up from the floor carpet. The aftermarket mats do not have the ring clips that the OEM mats have. Instead they have molded indentations in the mats and the indentations sit over the floor pins without locking into place! By not having ring clips, water cannot drip onto the carpet...but then the mats do not have a means to lock onto the floor!
Over the next 3 years, it appears that the indentations no longer sit well on the floor pins...the mats tend to start to slide
My carpets are black and so are the aftermarket mats. It is very difficult to see precisely where the mats are positioned when you are sitting in the Mustang.
1) The mats were sitting correctly with the driver's mat laying under the gas petal when I left home.
2) When I got out at the parking lot...I had to swing my legs back from under the dash. The mat then slid back several inches.
3) When I got back in...I had to swing my legs under the dash...the mat slid forward. But because the mat has a 'boat-bow'-like up-turn on the front...the mat has two possible positions. Slide under the gas pedal or slide over the gas pedal.
4) This time the mat slid over the gas pedal!
5) Because the carpet is black and so is the mat...and my legs sit so far forward under the dash, it is essentially impossible for me to see where the front of the mat is without turning up the ambient underdash lights or using a flash light.
6) Just the weight of the mat on the electrically controlled gas pedal moves the pedal position enough to cause the engine to rev to above 3000 rpms when I started it.
7) Because I didn't notice the mat on pedal...it over-revved during the next few starting attempts.
8) I got out of the Mustang to try to figure out what was going on...the mat slid back toward the seat as I swung my
legs...uncovering the gas pedal.
9) when I got back in...the mat slid forward...but this time it slid under the gas pedal, and it started correctly.
The mat has a 50/50 chance every time I get into the car to slide over the gas pedal.
I removed the mat and found that the indentations were no longer sharp edged (that could grip the edge of the floor 'pegs')
so the mats are able to slide more easily the more often you enter and exit the car.
I talked to my local dealer and he said that he has found that the aftermarket brand mats I had bought do tend to slide more as they age. It's one of the first things he checks when a customer comes in and complains about an over-revving engine when starting.
I have ordered some do-it-yourself ring clips that I will install in my floor mats...that way the mats will have a positive lock
onto the floor. The mats will not be able to contain as much volume of water but at least the mat will not be able to slide on top of the gas pedal.
My mats that did not have snap lock rings and helped develop this potentially dangerous situation were Weather Shield. Weather Shield is know for making 'tub type' liners. If they used snap rings, water could seep into the carpet through the ring holes. Engineers tend to be linear thinkers...one line of thought without thinking about any potential problems that their design may produce.
I finally figured out what was going on. When I bought the 2015 convertible, I replaced the OEM floor mats with the most popular 'pan-type' floor mats. To remove the OEM mats, one must pop the mats off of their 'mushroom' plastic pins that extend up from the floor carpet. The aftermarket mats do not have the ring clips that the OEM mats have. Instead they have molded indentations in the mats and the indentations sit over the floor pins without locking into place! By not having ring clips, water cannot drip onto the carpet...but then the mats do not have a means to lock onto the floor!
Over the next 3 years, it appears that the indentations no longer sit well on the floor pins...the mats tend to start to slide
My carpets are black and so are the aftermarket mats. It is very difficult to see precisely where the mats are positioned when you are sitting in the Mustang.
1) The mats were sitting correctly with the driver's mat laying under the gas petal when I left home.
2) When I got out at the parking lot...I had to swing my legs back from under the dash. The mat then slid back several inches.
3) When I got back in...I had to swing my legs under the dash...the mat slid forward. But because the mat has a 'boat-bow'-like up-turn on the front...the mat has two possible positions. Slide under the gas pedal or slide over the gas pedal.
4) This time the mat slid over the gas pedal!
5) Because the carpet is black and so is the mat...and my legs sit so far forward under the dash, it is essentially impossible for me to see where the front of the mat is without turning up the ambient underdash lights or using a flash light.
6) Just the weight of the mat on the electrically controlled gas pedal moves the pedal position enough to cause the engine to rev to above 3000 rpms when I started it.
7) Because I didn't notice the mat on pedal...it over-revved during the next few starting attempts.
8) I got out of the Mustang to try to figure out what was going on...the mat slid back toward the seat as I swung my
legs...uncovering the gas pedal.
9) when I got back in...the mat slid forward...but this time it slid under the gas pedal, and it started correctly.
The mat has a 50/50 chance every time I get into the car to slide over the gas pedal.
I removed the mat and found that the indentations were no longer sharp edged (that could grip the edge of the floor 'pegs')
so the mats are able to slide more easily the more often you enter and exit the car.
I talked to my local dealer and he said that he has found that the aftermarket brand mats I had bought do tend to slide more as they age. It's one of the first things he checks when a customer comes in and complains about an over-revving engine when starting.
I have ordered some do-it-yourself ring clips that I will install in my floor mats...that way the mats will have a positive lock
onto the floor. The mats will not be able to contain as much volume of water but at least the mat will not be able to slide on top of the gas pedal.
My mats that did not have snap lock rings and helped develop this potentially dangerous situation were Weather Shield. Weather Shield is know for making 'tub type' liners. If they used snap rings, water could seep into the carpet through the ring holes. Engineers tend to be linear thinkers...one line of thought without thinking about any potential problems that their design may produce.
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)............until one day the mat moved forward just as I was accelerating. Nothing focuses the mind like your car hitting the red line without your foot on the pedal................especially as I was following my friend in his gorgeous '68 Fastback 
