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View Full Version : Spark plug change in 99? - RC12ECC


goldygopher
April 11th, 2012, 00:55
I've been searching about this for an hour and was curious if anyone can enlighten me...

'91-98 calls for RC12LYC (Champion 412)
'99-01 calls for RC12ECC (Champion 438)

Why the change in 99? Of course I'm still running a distributor on my '99, but the underhood sticker and all applications list the later plug. It would make sense in '00-01 with the change to coil packs.

Is there a dimensional difference between these two? Only difference 98 to 99 I can think of is the intake manifold.

I know the 438's will work, but I just would like to know if the 412's are a better option...

Wayne Sihler
April 11th, 2012, 05:18
The later plugs have a double platinum electrodes--distributor less models fire twice per revolution..once the normal way/once the reverse way (+>-, and ->+)
Different metal in the std plug,,,,or so it was explained to me,,,

Tim_MN
April 11th, 2012, 08:47
Find the Champion specifications for each part number and compare them. One can reasonably assume that the change to the new design intake manifold is the reason for the spark plug change. I would just use whatever plugs it says to use.

goldygopher
April 11th, 2012, 10:10
Both are still copper plugs. I see no differences in these specs. I guess I'll just get the 438's. Still would like to know why...

438
http://www.sparkplugs.com/services/image.asp?path=http://www.sparkplugs.com/productImages/2/438.jpg&width=130&height=250

14mm Thread Size, 19mm (3/4") Reach, 5/8" (16mm) Hex Size, Gasket Seat, Resistor, .290" Projected Core Nose, Copper Core, Heat Range 12

VS

412
http://www.sparkplugs.com/services/image.asp?path=http://www.sparkplugs.com/productImages/2/412.jpg&width=130&height=250

14mm Thread Size, 19mm (3/4") Reach, 5/8" (16mm) Hex Size, Gasket Seat, Resistor, Copper Core, Projected Core Nose, Extended Electrode Gap, Heat Range 12

Talyn
April 12th, 2012, 07:32
The later plugs have a double platinum electrodes--distributor less models fire twice per revolution..once the normal way/once the reverse way (+>-, and ->+)
Different metal in the std plug,,,,or so it was explained to me,,,

Whoever explained that you should stop talking.

Later models never had platinum plugs, always copper. The distributor less models came in 00 on the XJ (99 for TJ and WJ). His is a 99, so he still has the distributor. It is true that the distributor fires twice per revolution, but it never reverses polarity. The way it is setup on the 4.0L is that it fires cylinder 1&6, 2&5 and 3&4 at the same time. The coil rail has 3 coils and they are paired that way. When #1 is on the firing stroke, #6 is on the exhaust. The cylinder on the firing stroke will get the greater spark because there is less resistance between the plug gap in the cylinder with gas and compression. The cylinder on the exhaust stroke will just fire to burn any left over combustion products. Its also called a waste spark system.

Wayne Sihler
April 13th, 2012, 01:30
Whoever explained that you should stop talking.

Later models never had platinum plugs, always copper. The distributor less models came in 00 on the XJ (99 for TJ and WJ). His is a 99, so he still has the distributor. It is true that the distributor fires twice per revolution, but it never reverses polarity. The way it is setup on the 4.0L is that it fires cylinder 1&6, 2&5 and 3&4 at the same time. The coil rail has 3 coils and they are paired that way. When #1 is on the firing stroke, #6 is on the exhaust. The cylinder on the firing stroke will get the greater spark because there is less resistance between the plug gap in the cylinder with gas and compression. The cylinder on the exhaust stroke will just fire to burn any left over combustion products. Its also called a waste spark system.
Thanks for setting me straight.

crimsondragon
April 13th, 2012, 12:06
Quick look on Google says the ECC are double copper where as the LYC are single copper. Don't ask me what the hell that means.