How to Test Spark Plug Wires
Articles, Blog

How to Test Spark Plug Wires

September 13, 2019

hey guys chrisfix here today we’re going to diagnose bad spark plug wires I’m going to show you how to tell if a spark plug wires bed some symptoms might be a misfire in your engine you could be getting bad fuel economy you’re idling is weird it could be idling high or low there is radio noise interference like you hear a high-pitched squeal those are all indicators of bed spark plug wires I’m going to show you three different methods the first method is just going to be a water mist test and you’re going to do that at night the second method is a visual inspection and the third method is using a multimeter so we’ll cut the lights right now what you need is a water bottle a spray bottle set to mist you have your engine running so here your spark plug wires this is where the electronic distributor is and your spark plug wires go into the spark plugs in the cylinder heads what I’m going to do I’m going to shut the light on the camera and just take the spray bottle just plain water and mist it and what I’m going to look for our sparks sparks mean that the spark plug wire is shorting and arcing so you get the idea now I’m going to shut the light off right now I’m spraying on top of the distributor cap area hopefully that comes up on the camera now I’m moving over to the passenger side wires underneath where the wires meet the spark plugs I don’t see anything there and now I’m moving to the driver’s side I don’t know if you can see it sparking in the back there but they’re sparking it’s just like little flickers of light and now I’m going to try underneath I don’t see anything underneath so you just saw the water mist test and you saw it did spark so there is arcing so I’m going to show you the next way to tell if a spark plug wire is bad the second method is to visually inspect the spark plug wires now this could be difficult to do when it’s in your car so you might have to take them out and I have them out just to show you make it really easy for you to see so I have these spark plug wires side-by-side what we’re going to look for were three different things we’re going to look for corrosion on the metal pieces we’re gonna look for any burn marks and we’re gonna look for any cuts any cracks anything where there’s no insulation between the wire and the outside that will cause problem so we have a brand new wire here you can see right next to the used wire and the idea here is I want to show you the difference the metal on both the brand new one and the old one look the same there’s no corrosion that’s a good first step now we’re going to look down the spark plug wire and make sure there’s no cracks or burns and as we go past when I check all sides it might help to use some wd-40 to clean the spark plug wire you just spray it on there and use a paper towel to clean it off you can see here here’s some spots where the insulation is worn down because it was rubbing so that’s no good and the final thing is look for any cracks a lot of times it’ll crack near the boot that goes right next to the block because it’s really hot there and this actually looks pretty good you can see there’s a burn mark right there that’s no good I have an example of a bad spark plug wire that has a bunch of different things you can see this is where the clip was it kind of dug in and caused some problems there there’s a nice cut right there when you bend it it really opens up and right behind the crack you can see here there’s a really good burn mark and this thing is shot we’re going to replace the spark plug wires I’ll have a video at the end of this video to show you how I did it but again just for a summary you’re looking for little cuts little cracks anything like that you’re looking for burn marks and you’re looking for any corrosion that’s inside here or inside here so the next method we’re going to use test spark plug wires is using a multimeter we’re going to put it on Ohm’s and we’re going to check each wire so I’m going to use old and new spark plug wires to show you the difference I have a tape measure and I’ll explain why that’s important and I have an ohm meter this is actually a multimeter has a bunch of different functions what you want to do is look for the horseshoe that’s an Omega symbol and you want to set it to 20,000 when you make contact it tells you the resistance of the wire so this is the first test you want to do it you wanna make sure it’s working properly see how it changes and then when you let go break the contact it goes back to one so we’re using a tape measure because the resistance of a wire is measured by foot so on a normal spark plug wire you get about five to eight thousand ohms of resistance per foot now the newer spark plug wires today that resistance could go all the way down into the hundreds here is the spark plug wire that just showed you that has the burn marks and the cuts in it this spark plug wire is about 17 inches long I’m going to just take one side here and make contact with the metal and then take my other side and in here there’s a piece of metal as well and make contact and you can see that change to five thousand four hundred ohms so that’s actually not too bad the problem is right now the spark plugs bent and you can see there’s contact once I like unbend it a little bit you can see I’m moving the spark plug wire around it loses contact inside so that means there’s a fault in here so sure maybe this works some of the times but once it gets moved around a little bit you lose a connection in here and that’s no good so the spark plug wire is shot now I have this long spark plug wire it’s 32 inches long and here’s the matching one which is the same length and this is the brand new one so I’m going to do the brand new one first so you can see here the brand new one is 1500 ohms that’s pretty good for a over two foot wire so now I’m going to check the stock wire that’s old and see what that is and we can see the old one is ten thousand three hundred thirty three ohms so still within spec but not as good as the new spark plug wires so that’s how you check the continuity and ohms of a spark plug wire so those are the three different methods I have for you on checking your spark plug wires hopefully this video was helpful if it was give it a thumbs up that helps me out a lot on YouTube also consider subscribing I publish how-to videos weekly and you get some good info on how to check stuff how to diagnose stuff how to fix stuff it’ll save you a lot of money and they’ll keep your car in tip-top shape also check out my Facebook and Twitter links in the description below on the screen will be different videos on spark plugs spark plug wires how to change them all that stuff and you can just click on the videos on the screen or you could check out the link in the description below just in case you can’t click on the screen


  • Reply crazy coop March 31, 2019 at 6:10 am

    I have an 06 impala 3.9 and my wires run across the top of the block and one day i noticed they were shorting out on top of the motor it looked just like when you sprayed the water on them and i could see it around sunset so it wasnt even dark

  • Reply Nikith Klement April 9, 2019 at 3:27 am

    Please reply.. Does decarbonization needed in cars.. If yes can we have a video on that..

  • Reply Thang Tons April 20, 2019 at 12:32 pm

    Will weak coil cable cause low rpm??

  • Reply brandon webb April 22, 2019 at 12:28 am

    Can you do a video on timing a distributor

  • Reply Thang Tons April 23, 2019 at 12:54 pm

    Sir, my car i20 4th coil HT cable, the shortest cable, has 8.8 ohm resistance which is the highest among the 4 HT cables. The 1, 2, and 3 readings are…2.4, 2.0 and 1.8 ohm respectively. Is the 4th cable really defective???

  • Reply Mario Acosta May 9, 2019 at 3:11 am

    Fuel selector valve
    My truck selector valve is gummed up
    Can you do a video on how to diagnose and or repair , replace the selector valve? 1988 ford f 250 5.8l
    Thanks for your tutorial vids
    Mario A

  • Reply Troy Smith May 9, 2019 at 6:41 am

    10 thousand ohm's per foot divide that 12 tells per inch

  • Reply Jay Sayles May 18, 2019 at 1:18 am

    After you find the solution and replace the plug wires, will the engine light go out or do I have to clear the code?

  • Reply Quốc Huy Lê May 21, 2019 at 5:27 am

    Hello everyone, I have a Honda Accord 2002 LX I4 that have a check engine light is on. I have code P0420 two weeks ago. I use the lacquer thinner put in the gas tank and the code is gone. After 9 days, my car give me the code P1399 misfiring. I came to auto shop, my mechanic cleaning EGR, cleaning intake manifold, change head gasket, change spark plug and wire, change distributor, check compression, check vacuum leak… but the check engine light is still on and my car is likely losing power, hard to speed up and shaking when it is idle or running <15 mile/hr. I realized when I pull out the spark plug wire number 3, the rpm is not changed. So my question, is there any chance that the bad Oxygen Sensor or the bad Catalytic Converter give out the code P1399? My mechanic check all the above possibility that could cause misfiring but cannot fix it. I appreciate all comments and helps. Thank you so much.

  • Reply WorldRenownedCFE June 1, 2019 at 6:40 am

    Chris fix was hiding something a couple times in this video, the fact that it's hard to get these leads down inside the wires to even test them. he covered it up a few times in the video. why not just a continuity test?

  • Reply Ku Alex June 7, 2019 at 2:34 pm

    Thanks for what you done

  • Reply kennedy wong June 22, 2019 at 12:42 am

    Can brand new spark wire give bad ohm reading? I have very strange problem because my ignition coil running hot like microwave. I using brand new bosh spark wire. I test it and resistance are low,

  • Reply Adi Syahmi Haji Yusof July 3, 2019 at 7:53 am

    hey Chris, do you have a video on how to test ignition coil?

  • Reply Debbie Bethel July 5, 2019 at 9:51 am

    Get the hell off my utube i am not sharing

  • Reply Josediego Lopez July 13, 2019 at 10:06 pm

    Thank you dude i learn something .

  • Reply Thang Tons July 15, 2019 at 3:51 am

    What a genius information. Thanks for sharing.
    I replaced the bad coil HT cable 4 which has over 13kohms as against the specs 1kohm.

    But something surprise again, the same car i20 has 2 separate coil packs controlled by 2 wires connector which controls 2 high output terminals. However, one high terminal pin 4 of first coil gives less spark than pin 1 on the same coil pack. Why such less spark being provided by the same primary coil of the same coil pack?

  • Reply halpati pratik July 19, 2019 at 7:09 pm

    Thank you sir this video is weary helpful fore me…
    Easy to diagnose the problem of missing and power loss of Care…….. 🚗🌫🌫🌫🌫🌫🌫🌫🌫🌫🌫

  • Reply Nouman Malik July 19, 2019 at 8:01 pm


  • Reply Rondo Schiavoni July 21, 2019 at 7:23 pm


  • Reply Lex Shizno July 22, 2019 at 7:05 am

    Weekly my ass

  • Reply Thefirstgalaxybeing August 10, 2019 at 3:16 pm

    I had 1 bad plug wire and  experienced CYL 2 MISFIRE, TRANSMISSION SLIPPING, OVERHEATING ENGINE. Radiator guy wanted to replace the radiator. Transmission guy wanted to fix the transmission. After checking the plugs, coil packs and wires, I replaced the wires for $29.00 from Amazon. No more problems.

  • Reply Benjamin Bugarin August 11, 2019 at 2:12 am

    That's good video.

    What about putting a performance set up. Low ohms. Would it cause interference with other electric components

  • Reply james davies August 23, 2019 at 4:08 pm

    I know a guy who got knocked on his arse with the spray bottle test. ended up in ER

  • Reply Thang Tons September 4, 2019 at 10:46 am

    My car i20 clutch sets …disc, bearing and plate, and slave cylinder has been changed recently. After that, all working ok…pulling, shifting, etc..all ok. No complaints.

    However, just about 3000km of driving since the above replacements were made, the car suddenly failed to engaged any gear while driving. The clutch pedal all the way goes to floor and never return back. I have to manually return to its original position and then pressed again repeated. However, it still sticks to the floor and never return back.

    I was driving and all of sudden the issue happens. Stuck in traffic and was pull over to roadside with traffic police help.

    Wait for some time, and yes, it come to engaged and disengaged again. All ok. But, the problems arise intermitently!!!

    There is no physical leakage, damage or low fluids in the system. All ok. (It used to happen when clutch is used often ie in traffic jams, clutch engaged and disengaged frequently, just in 10 minutes or so. However, no issues with pulling power and no clutch slippages, temperature, coolant all ok.)

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