A little history: I brought my car to the dealer two weeks ago complaining of a rough idle right before accelerating from a stop. They replaced the spark plug wires on the back two cylinders closest to the firewall (left and right), so 4 wires total. They also suggested replacing the spark plugs, for $750. I said no thanks to the spark plug change, and went on my merry way. The car drove fine after leaving the dealership, and there was no more rough idle.
Fast forward two weeks later, to this past weekend. I bought new Bosch platinum OEM spark plugs online and started changing them all out. The spark plug wires seemed very straightforward, as the top of each coilpack is labeled "a" and "b", and on the engine right by each spark plug, is also labeled "a" and "b". So I figured, wire "a" goes into spark plug "a", and wire "b" goes into spark plug "b", right? Well I got to the last cylinder closest to the firewall on the driver's side, and noticed that the "a" wire was plugged into the "b" spark plug, and the "b" wire was plugged into the "a" spark plug. These were 2 of the 4 wires that the dealership had changed two weeks ago. I was, like, WTF????? After changing all the plugs, I connected the wires the same way for that cylinder (what appeared to be the wrong way), and the engine started up fine. Drove it for a day, and everything seemed fine. I then convinced myself that there's no way that's right, and switched the wires on that cylinder, so that wire "a" plugged into spark plug "a", and wire "b" plugged into spark plug "b", just like all the rest of the cylinders. Started up the car, and it sounded fine. I then took it for a long drive, and everything seemed fine.
So. . . did the dealer definitely cross the wires on that cylinder, or is there some secret that we don't know about, where the cylinder closest to the firewall on the driver's side needs to be crossed that way? If the dealer crossed the wires, why did it seem to have no effect on the engine?
Sorry for the long post, but I'm now very curious as to what others out there think. Thanks!
Last edited by roadrunner117 : 06-26-2007 at 05:45 AM.
That being so, surely a and b should both fire at the same time, so it will not matter if they are crossed over. Just my hunch.....
Yes, two plugs per cylinder. That sounds like a reasonable guess, and it would make me feel a lot better if that were definitely the case. Anybody else have any input?
Both plugs do not fire at exactly the same time. One will fire just a tad later. You're just changing which plug fires first. You'll probably never notice any difference, even if you swapped them all.
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roadrunner: any other tips on the spark plug change?
I just followed the DIY instructions with pictures that I found here on this board. The offset 17mm wrench worked very well for removing the spark plug boots. The thing that took me the most time was pushing the spark plug boots back into the spark plug, especially on the driver's side where there wasn't enough room for me to get any kind of leverage. I kept on putting more and more dielectric tune up grease on the boots until I was able to push it in there. Hopefully I didn't put too much of it.
It took me about 3 hours, but I took my time making sure I did everything right. I even used a beam-type torque wrench that I got at Sears for $30, and I torqued the plugs to 20 ft-lbs. Three or four of the old spark plugs had oil on the threads. I'm not sure if that's a problem or not. Anyway, the next time I do it, it will probably take me half the time, since I now know what I'm doing.
Also, I was probably scratching my head and pacing back and forth for a good 30 minutes wondering why the spark plug wires seemed to be crossed on that last cylinder.
2 plugs per cylinder is the same set up as a Nissan 200SX or 240SX. Per cylinder, it takes 2 plugs, 1 for the intake and 1 for the exhaust. I found this a little odd but when I talked to an Indy, he said that it is more of an emissions matter than performance.
The second plug fires during the exhaust cycle to burn up unburned fuel.
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2 plugs per cylinder is the same set up as a Nissan 200SX or 240SX. Per cylinder, it takes 2 plugs, 1 for the intake and 1 for the exhaust. I found this a little odd but when I talked to an Indy, he said that it is more of an emissions matter than performance.
The second plug fires during the exhaust cycle to burn up unburned fuel.
But does it matter if you cross the wires on those 2 plugs? It apparently had no effect on my engine.
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