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Test test test NOT guess guess guess
Idle vacuum fluctuating (SP)?
EGR vacuum pots clean and operational?
Smoke tested entire intake system for leaks?
Cleaned the throttle body plate and replaced the mounting gasket?
Cleaned & Replaced the cam sensors seals?
Removed and replaced all the plugs with known good NGK plugs?
Recommendations:
There are three plugs recommended for the 4.8is from NGK
OE NGK ZFR6FH-11, Stock number 4294. Iridium 0.8 center electrode with a platinum ground electrode plug. Factory gap of 0.044 inches
Iridium IX NGK ZFR6FIX, Stock number 6441 Iridium 0.6 center electrode Tip (copper core) with a cut back and tapered platinum ground electrode plug. Factory gap of 0.044 inches.
The big difference between the OE plug and the IX is the additional engineering and trimming steps to provide better anti-fouling, easier cold starts, better tip in acceleration, and the shells are coated with anti-corrosive and anti–seizing materials.
The recommendation is always go with the plug that will provide the best performance over the widest range of driving. In our applications I would go with the NGK Iridium IX plugs every time. Will the smaller center electrode wear faster? Yes, in a lab. You will get 60K out of them easy.
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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
Last edited by StephenVA; 03-16-2023 at 10:01 AM.
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