Spark Plug Recommendations

[jblack]

I've got a 2003 3.0L Z4 and I'm thinking about changing the spark plugs and wires. I'd like to stay below $8 per plug.

Other Questions:
-Do I need to gap the plugs?
-Should I torque these down to a certain specifications or is it fine if I just do them till they are snug?
-If I need a torque wrench, I was thinking about buying local so maybe I could get a loaner torque wrench.



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The car has 77K miles and the reason I'm thinking about changing the plugs is the car has been to the shop twice in about 2 months for a misfire on cylinder 5. This last time they cleared the codes and didn't charge me. The problem only pops up every once in a while. While talking to the guy at the shop he indicated the plugs are $20 each because they are platinum (I'm thinking it is more because this is a BMW). If I change the plugs and wires and the misfire returns, I know the problem is with the coil. I'm not sure if the plugs have ever been changed as we've only owned the car for about 17 months. I'd just go buy what the auto store recommends, but I know this car is picky. I've done some searching but haven't seen any suggests for the standard Z. The car is completely stock.


Any help and suggestions are much appreciated! Thanks!

[blender]

Iridiums. Yes on the torque wrench. Some stores rent tools. Have fun.

[thekurgan]

Denso or NGK iridium are great plugs, torque is 17 ft-lbs, no grease or anti-seize and you should be fine. They do need to be gapped, I found variances from .028 and .035 on the NGK iridium plugs.

[XMetal]

I think the 3.0i uses the laser platinum 4 prongs (OEM) - NGK (3199) BKR6EQUP or the equivalent Bosch version. These do NOT need to be gap.

[sbtwister]

I went with the NGK Iridiums as well, and I am very happy with them. Performance is very crisp, engine seems very happy. No gapping was necessary. Definitely yes on the torque wrench.

[thekurgan]

Originally Posted by sbtwister

I went with the NGK Iridiums as well, and I am very happy with them. Performance is very crisp, engine seems very happy. No gapping was necessary. Definitely yes on the torque wrench.

Did you check the gap? I found them to be quite different from plug to plug.

[santov]

I went with the Bosch +4. I normally don't like the multi-prong spark plugs, but my Z4 loves 'em and runs really smooth. Used same Bosch +4s on neighbors 530i (different part number tho) and his engine ran MUCH smoother.

In both cases Kragen's had them cheaper then anywhere else. Even had a $1 rebate for each plug [at the time].

[santov]

Oh, I know this will make me sound old fashioned and go against the BMW grain:

I use a little copper anti-sieze on each plug (applied a small amount with a qtip). And I only tighten to snug.

I prefer anti-sieze, as you can feel the corrosion/carbon build up and resistance when you take the old plugs out. The BavAuto blog mentioned using copper anti-sieze on the coil to plug connection too. I used a little too.

As for going to factory torque of 17lbs, it makes me nervous as the aluminum heads can fatigue. I had a honda accord with aluminum heads and the threads started to strip, and I only got to 12lbs out of 15lbs. IMHO I don't think +/- xx lbs is going to make a difference as the plugs are seated against the crush washer and head and there's no way it's going to work out.

YMMV.

[wonton180]

If you bought the car stock and you have 77K miles, it's an almost certainty your plugs are original. ....and they're due to be changed! Change the plugs first (don't swap/touch the coils), and your misfires will disappear.

I had Bosch+4 on my 3-series a while back. The engine definitely ran a bit smoother with these plugs but caused crazy engine management codes/misfire at the END OF THEIR LIFE. For the first 60K, they were great! The OEM plugs cause simple misfires or acceleration studders.

BMW and my indy shop still recommend the OEM (NGK) plugs which I did after that event.

[jblack]

Thanks everybody for the replies. I got the NGKs Iridiums. I just have to put them in. Why do you recommend not using anti-seize? I got some just in case because it was cheap ($1.30 for a packet).

I did some googling and found this: http://bmwmotorcycletech.info/sparkplugs.htm (Skip down to the section on Antiseize compounds)

I know it is about motorcycles, but I figure that when it comes to spark plugs the same rules would apply. He says if you use anti-seize that you need to lower the torque on your spark plugs slightly less than 1/3.

I'm just curious as to why I shouldn't use the anti-seize.

[thekurgan]

New plugs have an anti-seize on the threads already, as part of the plating, using the anti seize will also alter the torque value when you torque them down, potentially over torquing them. Also, you'll find those are NOT pre-gapped. On my second set, they range from .028 to .-35. Make sure you gap them. BMW also specified "ungreased" as well, so skip that dilelectric stuff.