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Old 09-16-2015, 10:57 AM
StephenVA StephenVA is offline
Join Date: Jun 2013
Location: Virigina, USA
Posts: 2,040
StephenVA is on a distinguished road
In the automotive testing world, coils are only replaced upon failure as some will last a lifetime, others overheat, melt their cases, and/or short out.

When cars had one coil and a distributor that sent the pulse to the right cyl at the right time, everything gets replaced at the same time- Coil, coil wire, cap, rotor, plug wires, plugs. With today's coil on plug technology, the correct service pattern is to replace the failed unit - coil (boot if applicable) and plug. Is the complete set of coil replacement a good practice? It would not hurt (only the costs would). I would recommend replacing only the failed one(s) as the other 5 or 7 would run and perform as new for many more service cycles. In a DIY world all bets are off as the only costs are parts.

In any event replacing all the plugs at sooner than recommended intervals is ALWAYS a great choice. If one fails, replace all. Hell once your in there and you have all of them out, why reinstall old wear parts like a plug? They are cheap enough to pull, inspect, and the replace on a regular basis. On street muscle cars, I used to replace them every year as normal service. Race cars every race, timed run, or test cycle. Verify on a scope and off they went. Testing only takes a few minutes with proper equipment.

With the right scan software and the on board systems, X5 owners can read miss fires by cylinder stored over time. What more can you want? Botton Line: When in doubt replace!

2005 X5 4.8IS
The Blue ones are always FASTER....

Current Garage:
2005 X5 4.8is
2002 M5 TiSilver
2003 525iT
1998 528i
Former Garage Stable Highlights
2004 325XiT Sport
1973 De Tomaso Pantera, L Model
1970 Dodge Challenger T/A 4 sp Alpine White
1970 Dodge Challenger T/A 4 sp GoManGo Green
1971 Dart Sport, “Dart Light” package
1969 Road Runner 383
1968 Ply Barracuda 340S FB Sea-foam Green
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