Need help understand sparkplug wire ohms?

[unioncreek]

I've been having problems with my 03 Impala having no acceleration and misfires under hard acceleration. I put in new sparkplugs, but not wires. I checked the ohm's on each wire, but don't fully understand the numbers. I google testing wire, but what it said what if you numbers are less than 6 when the meter is set at 20k then replace the wires.

Here's what I get when I have the meter set at 20k:

#1 1.32
#2 4.21
#3 1.90
#4 4.20
#5 2.47
#6 4.68

Any help would be appreciated.

[procaddytech]

Spark plug wire resistance spec. for 2003 Impala is 3,000 ohms per foot max. Yours seem fine as long as the insulation is good and they are not arcing to ground or cross-firing. (I'm guessing your readings are in k-ohms?) Check the coil towers for corrosion. There are many other things that will cause misfires of course. If the wires are O.E. I would recommend replacement based on the age of the wires. Impalas of this era are also known for catalytic converter restrictions causing poor accceleration. A backpressure test will prove converter good or restricted.

[unioncreek]

Procaddytech,

Someone mentioned the cat to me also. They said to drill a hole before and after the cat and test the pressure. How would you suggest testing the pressure? Some also suggested checking the temp before and after the cat and if it was high before the cat that is was not functioning correctly.

Bobg

[procaddytech]

No need to drill holes, they are already there. Remove the oxygen sensor before the cat. and test the backpressure there. If you can rent or borrow a backpressure tester it is made to screw right in. The pressure should not exceed 1.25 psi at idle up to 2500 rpm. If the pressure is high, then remove the O2 sensor behind the cat. and test there to see if there is restriction behind the cat. (pieces of cat in mufffler etc.) Sometimes you can just bang on the cat. while it is COOL and if you hear it rattle inside then it has come apart internally and the pieces are causing a restriction. If you cannot find a backpressure tester and are in an area where you can test drive without exhaust, remove the exhaust from the manifold flange, let it drop back a few inches and see if the sluggishness is gone. You may want to tie it down with wire or a big tie strap. I have never tried the temperature test so I cannot comment on it's effectivenes.

[unioncreek]

Thanks Procaddytech,


I'll check to see if I can rent a pressure tester. If I can't what is the thread size on a O2 sensor? I can rig something up.

Bobg

[procaddytech]

18mm x 1.50mm. I made an adapter by cutting the hex and thread portion from an old O2sensor, drilling it out a bit and welding on an air fitting nipple. I just connect my vacuum/pressure gauge to the nipple via some hose.

[Tech II]

Testing ohms is just one test........resistance wires tend to be much higher than performance wires, so that they don't cause radio interference....different brands can vary greatly.....2K per foot....5K per foot.....10K per foot......best way to check wires is measure the resistance of each one, and then divide by length in feet(so say the wire is 18'', that converts to 1.5'....should all be consistant in a set of wires....

But like I said, that's just half the story.....a spark may jump from the insulation....two easy ways to check.....one, spray wires with a water/salt solution and looking for a spark....the other way, ground a test light and run the probe end along the wire.....you will see a spark jump to the probe end if there is a break somewhere.....

[j cAT]

Originally Posted by unioncreek

I've been having problems with my 03 Impala having no acceleration and misfires under hard acceleration. I put in new sparkplugs, but not wires. I checked the ohm's on each wire, but don't fully understand the numbers. I google testing wire, but what it said what if you numbers are less than 6 when the meter is set at 20k then replace the wires.

Here's what I get when I have the meter set at 20k:

#1 1.32
#2 4.21
#3 1.90
#4 4.20
#5 2.47
#6 4.68

Any help would be appreciated.

the wire resistance with your vehicle should not be from 1-4.5K ohms. when on the 20 K ohm range a reading of 1 is 1k ohm. the wire resistance of all the wires should be close to the same value/NOT THE SAME BUT CLOSE ! #2 #4, AND 6 ARE TOO FAR OFF..

when these wires go bad the resistance gets higher . this is due to heat damage. always use OEM spec wires. do not use aftermarket high performance junk. wires are designed with the proper resistance so the the ignition spark system works correctly.place dielectric grease in the boot ends to help prevent failure and to ease on future wire removal.

loosen the O2 sensor when the engine is hot. then remove the sensor after it cools off. this will help in removal. then with the sensor hole open go for a drive see if the power returns/runs better.

yes a bad wire can very well damage the converter as well as other components.

[Tech II]

2-4-6 are higher because they are LONGER.....

[j cAT]

Originally Posted by Tech II

2-4-6 are higher because they are LONGER.....

not that much longer 2X ?

usually the wires in the back , firewall area get the heat causing them to increase in the resistance.

not that this is the cure for his problem .

I would get new OEM spec wires with what resistance shown.