Flaps? What flaps?
AO Silver Member
Join Date: Oct 2014
Location: United Kingdom
Any power loss or smoke lower down in the rev range?
As you've described it, it sounds like the turbo is overboosting.
Usually between 3000-4000 rpm the VNT mechanism moves the turbo from high-boost to low-boost positions as the exhaust gas flow increases.. If the VNT mechanism is sticking then the turbo can hang up in high-boost position for too long, causing the over-boost error (and associated Motor Control System Failure message, and the low power "limp mode" to be activated).
Best way to progress will be to get a diagnostic computer plugged in to read the error codes, and then proceed from there. No point spending money to fix things until you've got a firm diagnosis!
Another route of attack could be to buy a bottle of turbo-cleaner (Archoil products are pretty good I've found), follow the directions and see if that clears it up at all.. If it is sticky veins, and it's just started, then an in-tank turbo cleaner solution could be enough to revive it... Nice long high-speed motorway runs are good too.. You can easily get up to 80mph+ without touching 3000rpm, so should manage to get up to speed without the MCSF dropping you into limp mode.. A nice long hot run can really blow out the crud on these engines... Also might be worth popping out the MAP sensor and inspecting it.. If it comes out looking like a lump of coal, it needs a clean!