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Thread: Z4 Roadster (E85) 03 Z4, couple of problems.
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Old 11-19-2012, 09:02 AM
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shipkiller shipkiller is online now
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As others have stated, I personally would replace the spark plugs and run a few tanks of fuel system cleaner through the engine if you are using the generic fuel cleaners.
The absolute BEST fuel system cleaner is something called BlueChem Fuel System Cleaner with number two being BG Products 44K. One treatment is usually sufficient to clean the entire fuel system. Then run a can of cleaner every 3000-5000 miles.

On your misfire, is the SES light steady or blinking? A steady light indicates a minor misfire and a blinking light indicates a major misfire. You are at the point, mileage wise, in your car that you can start to experience cascading coil failures. Replace one failing coil and another one goes out. The reason this happens is that when a misfire occurs, the DME attempts to compensate for the misfiring cylinder and any already weakened coils might fail. You might want to consider replacing all six at once. I did this on my wife’s roadster when the coil cascade failures started. If I remember, all six were about $150.00 from Bravarian Auto.

If coils do not fix the misfire issue, then either the wiring from the DME to the coil is at fault or the DME. It is a straight shot from the DME to the coil….

One other thing, I have seen coils operate properly in one cylinder but not another. So sometimes swapping coils for troubleshooting does not work…. Just be warned

As for the vanos O-rings being bad, yea they are. Is it catastrophic? No… just a minor performance lag issue. A vanos O-ring replacement is not really hard, just time consuming. I did this myself back in 2008 or 2009. Took about four hours.
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