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Re: How to check/change spark plugs Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Mon, 19 Jan 2009 10:42:48
In Reply to: How to check/change spark plugs, 9kSilverAero, Sun, 18 Jan 2009 14:24:32 Members do not see ads below this line. - Help Keep This Site Online - Signup |
I'll add a bit more - This may be tons of detail, but it's all very easy.
to remove the DI - remove the four screws (with the proper torx driver. Grab the sides (narrow bit) of the DI, and gently lift. I like to rock it side to side slightly.
I replace the spark plugs one at a time. Dropping stuff into the cylidner isn't a good idea, so the fewer holes open at once can only help.
You will need a spark plug socket - they come in different sizes. Many have some foam that holds the plug in place - a nice touch. Unscrew the plug (counter clockwise - lefty-loosey, righty-tightey. ) They might be a little stiff. Unscrew the plug and look at it. It should be a pale grey. White is lean running, black is rich running. The electrodes should have nice edges - if they're rounded, the plug is tired.
See some nice pictures here:
http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp?mode=nml
To check the gap of a plug, get a plug gapper, available in any autoparts store or most stores with an automotive department. Like mousetraps, they come in a wide variety. I like the simple disk - it's just a disk a little bigger than a quarter, and the edge is a slowly varying thickness, with dimensions engraved in it. Stick the thin part of the disk between the electrodes, and rotate the disk until it just stops. Don't force anything. Then see the number that lines up with the electrode.
Yes the electrode has thickness. I use the largest number at the edge of the electrode. If the gap is too small, carefully bend the electrode with the gapper. A little at a time. If it's too wide, I usually tap on the electrode to bend it down. Again, we're talking very small adjustments here, so force isn't necessary.
What plugs and what gap? Use ONLY the NGK's specified in the manual. I don't care if the guy at the autoparts place says the BelchFire 5000 is a direct replacement, or will give you 37.4% better gas mileage and good hair. The DI was designed to work with those specific plugs.
I believe the max gap is 1.0 mm / 0.040 inches. Err on the side of slightly narrower. Slightly is slightly - 0.95 mm, 0.038 inches is fine. Too wide, and the engine will misfire under boost. I've seen cars misfire at 0.043 inches/ 1.1 mm. Again, check the manual.
You can buy plugs pre-gapped - that'll be a -11 afterwards, for example. I don't care - I always check the gap before installing, and set it as it should be.
Note that to fit the DI properly, the plug needs to have the little 'cap' screwed onto the top. Some plugs come with it installed some have it rolling around in the box. The plug going in should look like the plug coming out.
Before installing, put a dab of anti-sieze compound on the threads. This is something else available in any autoparts store. A small can will last for years. Just a dab - you don't need to goop it on. And it gets on your hands and clothes, so watch where it goes. There are a lot of different anti-sieze products, and I can't claim any one is better (or worse) than the other.
I slip the plug into the socket, and with the socket on an extension, THREAD IT IN BY HAND - no ratchet. Sorry for shouting. It should start threading in smoothly. If you feel resistance, back it out; you're not screwing it in straight. It is possible to cross-thread a plug; that's why I turn the extension by hand - you can get a good feel, and you don't have so much mechanical advantage that you can force it and not know it. Screw it down until it provides some resistance, and then stick the ratchet on. Keep turning until it suddenly increases resistance. The plug has a shoulder, so once that hits, the force goes way up. At this point, tighten it down, but only slightly. You get the feel for it after a while.
Now, move on to the next plug. Note if one cylinder has a plug with a problem, (gap, looks, etc.)
Once the plugs are all done, put a dab of dielectric grease on the faces of the rubber DI boots - again, a big glop isn't necessary. Hold the DI over the plugs (cable side facing the battery - you'll have to work to get it wrong-way 'round), and lower it down and seat it. Screw down the four torx, and you're good to go.
Reading all of this takes more time than actually doing it. It's not hard. Just don't force anything, and you'll be just fine.
posted by 192.249....
, Mon, 19 Jan 2009 10:42:48 <-- Viewing This Message, Tue, 20 Jan 2009 06:06:51, Wed, 21 Jan 2009 11:12:29
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