DA40 Diamond Star
Flight Crew Commercial; Flight Crew Instrument
Flight Crew Last 90 Days 110; Flight Crew Total 267; Flight Crew Type 96
Aircraft Equipment Problem Critical
Air Traffic Control Provided Assistance; Flight Crew Diverted; Flight Crew Landed in Emergency Condition; Flight Crew Took Evasive Action
Aircraft
25 Nautical Mile from ZZZ on an IFR flight plan receiving vectors to final for the ILS approach into ZZZ the aircraft began to experience engine roughness. The engine instrumentation page indicated upon review shortly after the engine roughness that cylinder 3 had failed and shortly after that indication cylinder 4 had significantly lower EGT and CHT than 1 and 2. Shortly after that cylinder 4 began to perform normally. At this time we [advised ATC] and was receiving vectors to the nearest airport which was ZZZ1. Approximately 10 NM away from ZZZ1 the number 1 cylinder gave the same indications as the number 3 as in no EGT and CHT accompanied by further roughness produced by the engine. At this time the aircraft with maximum power applied the aircraft was struggling to maintain airspeed and altitude. Upon landing at ZZZ1 and parking the aircraft the engine died upon the closing of the throttle; which is the first item in the Shutdown Checklist given by the POH. No further incident.
Reporter indicated that maintenance discovered a failed #3 cylinder fuel injector.
25 nm from ZZZ on IFR flight plan with TRACON vectors for the ILS when engine roughness. Engine gauges showed loss of cylinder 3 and then cylinder 4. Cylinder 4 came back after 30 seconds. [Requested vectors] to the closest airport 9 nm away ZZZ1. Ran through engine roughness checklist and no changes. Lost cylinder 1; full throttle and hard to maintain 2;500 and 90 knots. Landed straight in ZZZ1. When throttle pulled to idle after clear of runway engine shut down. No interference with any other traffic during event.
DA40 student and flight instructor reported engine roughness led to a diversion. Later; Maintenance identified a failed fuel injector.