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      11-12-2012, 03:43 AM   #1
santov
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Drives: 2007 Z4 3.0si White over Beige
Join Date: Dec 2010
Location: Bay Area, Calif

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Go change your spark plugs! Right now!

Okay, not right now, but soon-

When I got my Z4 used as a lease return a couple years ago the first thing I did was change all the consumables. A little to learn the car, but also see what the fluids, etc looked like.

I changed the plugs with OEM Bosch plugs. 2 years and 28k miles later the idle when cold was a little erratic. Common when it was cold, but I was noticing that even when hot the idle was rough. Not necessarily a constant variation in RPM, but a vibration throughout the car. Like "boomy" reverbs through the cabin and I noticed ripples in my water bottle.

Since I was due for an Inspection 1 (DIY), I ordered up some plugs at the same time. This time I opted for NGKs.

Oh my gawd what a difference. Aside from looking at the tach you couldn't tell the engine was on. WOT accelerations weren't any faster, but they were so much smoother. Like the engine was pure electric.

I can't say the Bosch plugs were faulty, I did examine each one and no dark deposits or malformed contacts. Coil packs looked fine with soft rubber and good contacts at the wiring plug.

Same thing happened in my 2007 Honda Civic. The plugs were supposedly lifetime plugs good for 100k miles. At about 55k the idle got so annoying I took it to the dealer and they couldn't find anything wrong. The idle had become so rough my water bottle would rattle inside the cupholder, at a stop light! At the Honda parts dept they wanted $40 a plug since the were "special". I looked up the part number and bought replacement NGK irridiums for $8 at AutoZone. Huge difference after. Idle was incredibly quiet and accelerations were amazing smooth.

Hopefully somebody will read this and realize how easy it is to replace plugs. Your Z4 will appreciate it!
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