• Sign Up! To view all forums and unlock additional cool features

    Welcome to the #1 Fiesta ST Forum and Fiesta ST community dedicated to Fiesta ST owners and enthusiasts. Register for an account, it's free and it's easy, so don't hesitate to join the Fiesta ST Forum today!


Breaking up at 4000 rpm ONLY after long highway drives

Messages
35
Likes
6
Location
Miami
#1
My car a 2014 Oxford white sitting at 96000 miles that is stock except a mishimoto IC, mishimoto intake hose and drop in filter. After driving with cruise control for at least 30 minutes the car will break up when given wide open throttle application. After decreasing throttle input I repeat this process for three times before the breaking up goes away. I can't describe it as a misfire but like a rev limiter. Once it goes away the car runs perfect. I just changed the spark plugs after 96,000 miles and they looked fine. Even after reinstalling OE FORD spark plugs the problem remains. I have had instances where the car stalls after filling up with fuel and I wonder if that has anything to do with it. The tune on the ECU is stock and synthetic oil has been used since I bought it in April 2014.
 


Messages
184
Likes
46
Location
clermont
#2
apex,
being that you have 96000 miles on the car and it is direct injection do a search on carbon build up on the intake valves.i would be willing to bet that has something to do with it.are you using a catch can? good luck with it.
 


Messages
331
Likes
144
Location
Gloucester, VA
#3
Sounds to me like one of the temperature fail-safe rev limiters is activated by the likely high speed cruising. The oil temp goes higher than coolant temp at sustained high rpms.

A dealer should be able to download the ecu data and diagnos the problem. A Cobb AP could record the data as well.
 


Messages
424
Likes
133
Location
Palm City
#4
Maybe fuel pump is overheating, or radiator may be blocked / fans not operating correctly? Just a few thoughts.
 


haste

1000 Post Club
Messages
1,222
Likes
1,264
Location
Eastern
#5
I had this problem when using Cobb stage 3 and full bolt-ons. Since I've gone to a pro tune I haven't had the problem since.
 


lessard.dcj

1000 Post Club
Messages
1,560
Likes
140
Location
Petawawa
#6
i got this same issue when towing my 14 foot aluminum boat. (not very heavy) and i try to get on it. never had it happen when i towed my atv (much heavier) 8 months earlier. car just hits a rev limiter of about 4k.
 




Top