Engine Performance problem
2003 BMW 525 6 cyl Two Wheel Drive Automatic 65000 miles
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First noticed occasional clouds blue smoke from Exhaust. Then - after 3-4 days - EML light come on, loss of power and obvious misfire. Diagnostic codes P0300, P1345 - misfire Cyl 2 with fuel cut-off? and P1349 - misfire Cyl 4 with fuel cut off? recorded.

What is probable cause? With engine running, as each coil lifted out in turn, little change in engine note (so mechanic thought probably not coils!). Thought all petrol not being burnt fully. Smoke not continual. No previous engine trouble. Car is a UK, Sport model.

(Donation paid)

There is a device called a cyclone separator(at least thats what we call it on this side of the pond) that has a tendency to fail at the mileage you posted with.

Dr. Hagerty wrote:

There is a device called a cyclone separator(at least thats what we call it on this side of the pond) that has a tendency to fail at the mileage you posted with.

Main dealer garage "tested" and concluded needed a new coil Cyl 2 and new plugs (as fouled). Ran for short distance okish, but with peculiar apparent high petrol consumption. Within 3 days, same symptons of smoke, misfire, warning light reappeared.

Garage now diagnose from a raft of codes P0302, P0301, P1348, P0304, P1345, P1343, 0171, 0174 and apparently seeing somehow that misfire gets worse as it warms up (?) that HVAs are worn and need replacing (Hydraulic Valve Assemblies). But only done 64000 miles. Most misfire solutions on this site are electrical or fuel rather than mechanical.

Can garage be correct? Any further ideas?