I see that a lot of people are struggling with this kind of problems, so here are some suggestions how to resolve them, this could be a sticky thread (FYI).
Motor Control System Failure is universal message which appears on display when ever some error is recorded in engine ECU.
The safest way to determine the problem is connecting the car to diagnostics equipment (fo example K-line interface + FiatECUScan) and read which error is recorded, but here are some tips what else you should chack.
-> Possible problem
Black smoke on exhaust & loss of power (possible MCSF error)
-> usually split Turbo-Intercooler hose, or Intercooler-IntakeManifold hose, or cracked Intercooler, that causes losss of air pressure from turbo, and surplus of injected fuel is unburned and turns to black smoke (check the hoses http://i32.tinypic.com/2v3rbqv.jpg
and replace the cracked one http://i55.tinypic.com/2qs58yf.jpg
No power (no throtle response) below 2000rpm (possible MCSF error)
-> usually EGR valve is in stuck open position (there is a guide how to clean it and make it work again: How-to Fix the EGR on a 1.9JTD.pdf
-> if you physically block the EGR with blanking plate on JTD M-JET or JTDM you will get permanent MCSF error
-> also could be defective MAF (Mass Air Flow) sensor (try disconecting the el. connector from MAF and do a test drive, if engine performance is restored with MAF disconected replace faulty MAF with new one http://i34.tinypic.com/1idefc.jpg
No power below 3000rpm (possible MCSF error)
-> usually cracked vacuum hose for VGT regulation valve, so Turbo charger is always in high revs position (check these vacuum hoses http://i28.tinypic.com/2zqyc7q.jpg
, and replace the cracked one http://i31.tinypic.com/ele2z9.jpg
-> also may be jammed VGT regulation mechanism inside Turbo charger (Turbo charger http://i30.tinypic.com/2zgc2eu.jpg
needs to be disassembled and cleaned/repaired http://i30.tinypic.com/29g1l3b.jpg
Power cuts out after 2500-3500rpm (possible MCSF error)
-> usually jammed VGT regulation mechanism inside Turbo charger which is causing overboost and engine goes to SafeMode (Turbo charger http://i30.tinypic.com/2zgc2eu.jpg
needs to be cleaned/repaired: http://i30.tinypic.com/29g1l3b.jpg
-> also could be problem with faulty VGT selenoid (PIERBURG electro-vacuum valve #2 on pic. http://i28.tinypic.com/2zqyc7q.jpg
) (check functionality with diagnostics, and replace if faulty, on 156 http://i52.tinypic.com/2d75y1e.jpg
, on 147/GT http://i53.tinypic.com/rvzeyb.jpg
Reduced performance/power, car not able to acheive the maxiumum velocity (possible MCSF error)
-> usually faulty MAF sensor, showing wrong mass air flow which causes reduced engine power (try disconecting the el. connector from MAF and do a test drive, if performance is restored with MAF disconected replace faulty MAF with new one http://i34.tinypic.com/1idefc.jpg
Engine turns off when driving, or wont start (possible MCSF error)
-> usually failing crankshaft rotation sensor, or camshaft position sensor (to be sure check with diagnostics, and if one of these errors appears replace the faulty sensor)
Engine temperature between 50-60 degrees while driving
-> usually thermostat partially opened all the time, or opening to early, which is not good because combustion is not optimal and there is more soot generated in the engine (replace the thermostat, and temperature should be between 80-90 degrees)
More to come...