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Question(s):

  • What should the Resistance be for spark plug wires on a 2000 Blazer?
  • If they're supposed to be 2,000-3,000 Ohms, at what ohms should you look to replace them?
  • Is the resistance of all/most spark plug wires the same between vehicles?
  • Should I take the $30 Duralast wires back and get the $70 AC Delco wires?
  • Should Straight Booted wires differ in resistance from cornered boot wires? Because as the measurements suggest the straight ones are close to 3,000 ohms but the others are closer to 2,000 ohms.

Background:

I have been having misfires in my 2000 Blazer V6 4WD. I've done basic maintenance (Changed filters, oil change, etc.) and changed all 6 spark plugs.

I read that you could check your spark plugs using an ohm meter. I've read multiple inconsistent posts on what the Ohms should be some said 4,600 - 7,500, others said 50,000. I personally got around 2,000 to 3,000 for each wire when I measured (Assuming that 2.0 when the meter is set to 20K is 2,000 Ohms).

I just found this stating that the wires should be 1,200-1,500 ohms per foot. So 2,400-3,000 with my 2 foot wires.

New Duralast ($30) Spark plug wires (Measured in 20K Ohms setting):

  • Cornered Boots: 2.38, 2.37, 2.50, 2.13
  • Straight Boots: 3.01, 2.16

Old Spark plug wires (Measured in 20K Ohms setting):

  • Straight: 2.95
  • Cornered: 2.55, 2.32

(I only measured 3 because the others are a pain to get to)

Sorry for all the questions but I assume since they're all related it is okay to ask them in a single question. Please say so if I should split them into multiple questions.

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The purpose of the resistance in the plug wires is there so that the (1) plug firing voltage is great enough to maintain a sufficent spark firing time and (2) the resistance suppresses interferance with electronic equipment and radios. Spark plug wires are easily broken internally when being removed from the plug, as they can become attached to the spark plug. Try 'blipping' the throttle, pressing the throttle to raise the engine RPM to 1500RPM and releasing. If this is where your misfire is most pronounced then its a safe bet to change the wires. The higher voltage produced on initial acceleration will find any internal breakage and cause the misfire. 1500-2000 ohms per foot of cable is usually present, even on a bad spark plug wire, the misfire happens on the higher voltage. If you have a misfire all of the time, remove one one wire at a time with the engine running, with insulated pliers. When removing a wire which only makes a little or no differance to the engine RPM compared to the others will be the faulty wire. The actual resistance of any cable is down to its length, so differant lengths have differant resistances.

  • This is probably off-topic but, I just changed the sparkplug wires and the misfiring is worse. Any thoughts? I'm guessing I could have messed up somewhere putting them in so I'm going to double check once the engine cools. Is it possible I didn't mess up and changing the wires made the misfiring worse? If so, why? – Shelby115 Jul 13 '14 at 17:38
  • I would also like to mention, removing the spark plug wire while the engine is running is a good way to burn out your ignition system. Some vehicles (which include the Chevy models) are very susceptible to this, so is something you don't want to do. A better way to see if it's firing is to put a "noid" light in line. You can pick one up at most auto parts stores. – Pᴀᴜʟsᴛᴇʀ2 Jul 14 '14 at 1:14

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