ive got 05 137ps transit it has started show engine mangment light which cuts the power turning the key back then back on sorts it!!! it normally happens under throttle ive fitted new EGR valve so its not that.
try and get it onto a code reader and come back when you have the codes available,you could guess at a lot of faults,get nowhere and waste a lot of money
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Try fixfault.com to fix vans.