Plug wire resistance... why do I get odd values? 37 to 1k ohm
05-22-2010, 05:50 PM
#1
Plug wire resistance... why do I get odd values? 37 to 1k ohm Short version, where should I be "touching" to check the resistance of my spark plug wires? Depending upon where I touch, I've gotten 37 ohm to 1500 ohm
Long version, I burned the boots on a passenger side of my LQ4 thanks to an exhaust leak. I thought they were bad but upon checking the good side, I'm not so sure.
The "good" side also has the same issue where I can get 37 ohm to 1500 ohm depending upon what I touch.
On the spark plug side, I touch the fitting. On the coil side, if I touch the fitting, all of them get 1000+ ohm. But if I touch the center, I get ~37 ohm.
Long version, I burned the boots on a passenger side of my LQ4 thanks to an exhaust leak. I thought they were bad but upon checking the good side, I'm not so sure.
The "good" side also has the same issue where I can get 37 ohm to 1500 ohm depending upon what I touch.
On the spark plug side, I touch the fitting. On the coil side, if I touch the fitting, all of them get 1000+ ohm. But if I touch the center, I get ~37 ohm.
05-23-2010, 04:05 PM
#5
I would buy the meter being funky.
The thing that is odd to me is that the results are consistent if I use the same contact points. Dead center of the coil connection side and I get 37 ohm(I'm assuming that by going direct middle, I am hitting the wire core). The connector itself gives me the 1500ohm result.
The result didn't matter which plug wire I used(burned boot or good boot)
I'll post a picture of where I'm touching on the wires a little later today.
I'm trying to figure out whether I need to buy another set of new wires or if I just need to buy four boots. The wires have less than 50 miles on them. I'd rather spend $15-$20 on boots rather than $60-$70 on new wires.
The thing that is odd to me is that the results are consistent if I use the same contact points. Dead center of the coil connection side and I get 37 ohm(I'm assuming that by going direct middle, I am hitting the wire core). The connector itself gives me the 1500ohm result.
The result didn't matter which plug wire I used(burned boot or good boot)
I'll post a picture of where I'm touching on the wires a little later today.
I'm trying to figure out whether I need to buy another set of new wires or if I just need to buy four boots. The wires have less than 50 miles on them. I'd rather spend $15-$20 on boots rather than $60-$70 on new wires.
05-23-2010, 07:48 PM
#7
I won't deny that there is a good chance of a bad meter(see picture of Harbor Freight "junk")... but it is giving consistent readings for all the wires. I've got it dialed at 2k. It does zero out when I touch the two leads together.
According to this page: http://www.summitracing.com/parts/MSD-32829/
"core that has just 40-50 ohms of resistance per foot". Given these wires are under a foot, a measurement of 38 ohm seems about right.
As shown in the second picture, I'm dealing with a burned boot. That is the worst of the four. All passenger side boots were toasty.
In the third picture, that is what 4 of the plugs look like. I have a clear path to touching the plug side of the wire. On the fifth plug, while a little hard to touch the fitting, I am able to.
In the fourth picture, you can see the coil end of the plug. If I touch the fitting you see, I get 1500 ohm or more. If I touch in the dead middle without touching the fitting, I get the 38 ohm reading.
I can duplicate this on every "burned" plug wire as well as the good plug wire.
The issue I'm trying to solve is a misfire underload at mid to upper RPM.
According to this page: http://www.summitracing.com/parts/MSD-32829/
"core that has just 40-50 ohms of resistance per foot". Given these wires are under a foot, a measurement of 38 ohm seems about right.
As shown in the second picture, I'm dealing with a burned boot. That is the worst of the four. All passenger side boots were toasty.
In the third picture, that is what 4 of the plugs look like. I have a clear path to touching the plug side of the wire. On the fifth plug, while a little hard to touch the fitting, I am able to.
In the fourth picture, you can see the coil end of the plug. If I touch the fitting you see, I get 1500 ohm or more. If I touch in the dead middle without touching the fitting, I get the 38 ohm reading.
I can duplicate this on every "burned" plug wire as well as the good plug wire.
The issue I'm trying to solve is a misfire underload at mid to upper RPM.
