When to change spark plugs (6 tell tale signs)

when to change spark plugs imageSpark plugs are an integral part of your vehicles motor as they provide the much needed spark that ignites the air and fuel mixture within the cylinders. This continuous ignition is what keeps your car moving on the road.

If spark plugs are not checked with regular services, cleaned or changed when necessary, they can cause problems to occur with the vehicles engine. Below are six signs for when to change your spark plugs:

When to change spark plugs:

1. Engine has a rough idle

Your engine idles when it is a stationary and in this position the engine normally produces around 1000rpm. The sound the engine gives off is constant and smooth but if your spark plugs aren’t performing as they should, your engine will produce a rough and jittery sound while producing larger vibrations through the car. Not having this checked can lead to costly damage being done.

2. Having trouble starting your car?

Many people put their car not starting down to being out of fuel or having a flat battery. One possibility you may overlook is having bad or worn spark plugs. If your spark plugs don’t produce the spark needed to get the vehicle moving, then you’re going nowhere. It is also possible that faulty spark plugs are causing your battery to drain. If so you need to have your battery and spark plugs changed as soon as possible.

3. Your engine misfires

When your engine misfires it causes the vehicle to halt for a fraction of a second and then continues it’s usual movement. This means the vehicle isn’t functioning as smoothly as it should because one or more cylinders aren’t firing properly, which can also lead to higher amounts of emissions.

4. Engine surging

When a vehicle sucks in more air than usual in the combustion process it can cause the vehicle to jerk and then slow down or continually start and stop, which means the vehicles engine is working inefficiently. This is also known as engine hesitation and dangerous situation can arise if this occurs in traffic.

5. High fuel consumption

If your spark plugs have deteriorated you’ll notice that your vehicles fuel economy can decrease by up to 30% due to incomplete combustion. If you notice you’re having to fill up more often than usual it can be caused by deteriorating spark plugs. To get back to your vehicle’s optimum level of fuel consumption all you’ll need to do is have your spark plugs changed.

6. Lack of acceleration

If your vehicle is accelerating poorly it is fairly easy to tell. It feels as if the vehicle doesn’t want to respond when you put your foot down, or it does but not instantly as you’ve become accustomed to. It can also feel as if your vehicle is trying really hard to pull itself along. This ‘sluggishness’ can be easily fixed by having the vehicle serviced with a spark plug change.

If you’re not able to change the spark plugs yourself, it’s time to get your vehicle in for its next service. All Repco Authorised Service centres make sure to test all vital components like spark plugs in their safety checks. Contact your nearest Repco Authorised Service centre today to have your car back on the road and working efficiently.

Do you know any other signs of when to change spark plugs? Let us know in the comments below!

This is another post from Motoring About

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  • engine

    Yeah i .notice on 92.paseo my.car was.eating.alot.of.gas so.tomorrow morning going.to.change.it

  • Serain Jackson

    THanks for the info, it was very helpful, guess i need new spark plugs then.

  • Tanya Christie

    Thank you from Belize!

    • Ant Rod

      Belize Girls Are Sexy! mmmm….

  • kae

    I have pontiac g6 my car has start to skip, jerk, shake in front and cuts off when start driving but it still cranks.is it spark plugs

    • jackie

      this is the same issue I started having , my spark plugs and wires were coated with oil that it was burning. my engine (currently in the shop) had manifold gaskets that were breaking down so they are being replaced hopefully that is all that is wrong but I’m told it is NOT going to be a major issue due to the fact that compression is fine. Hope that helps give some insight ps I have a 06 pontiac g6

    • Ladyjacketscoach

      Having similar issues with my 07; jerk and gas cap sensor warning (even w/full tank). Also, the car is coding that my cam and crankshaft sensors are misaligned, but I doubt it’s a timing issue at 37K…Thinking it’s a coil issue because the car idles roughly when I turn the A/C on.

    • Josh Walker

      I would check plugs and wires. Usually you change both.

    • Meaghan Reimchen

      My g6 overcranks when starting, no balls no giddyup, just sort of sluggish… changed the air filter so I assume it is the spark

  • nadia

    Do you need to replace coils when replacing spark plugs ?

    • sliner

      usually no, unless you know for sure that you have a bad one

    • mk

      Categorically “NO”.

  • myrna houston

    there is a flickering, sounding like electrical coming from the area of spark plugs…like it is sparking in one of the cylinders…while in idle and not a smooth idle…?

    • CPinSL

      Sounds like your wires could be arcing. First, with the engine off, check the wires for cracks or see if they look all dried out. (Bending them gently in a loop will make the cracks very visible.) If that doesn’t show anything, then pop the hood in the dark (night)and watch for sparks to jump around by the plug wires. If so, replace all of them.

      If you’re really daring, you could run your hands around the plug wires and see if you get a heckuva shock. I myself wouldn’t, but YOU can! 😉

      • mk

        If I may “Pipe” in.
        In complete darkness, let engine run and look. You will see if there is crossfire from spark plug wires or coil. If you don’t see any sparking under hood than your issues are elsewhere.


    Thanks for the tips very helpful

  • Daniel Rafael

    What happen when the engine light star flashing 11times? Anyone can help me….and when i accelerating. The motor star shaking…

    • Inspiredam

      Daniel, this sounds like a serious problem and you should see a mechanic as soon as you can, otherwise you risk damaging your engine and potentially expensive repairs. The flashing light indicates that an error code is being sent from the central engine management computer – the best way to diagnose the error is to have a FC scanner connected to the vehicle.

    • Been there done that!

      My car did this and I read my manual. It said to turn the ignition off and wait ten seconds then restart. I had to read the manual so I didn’t try to start again for five minutes. But after that it started and the light didn’t flash anymore. I read some more and found I needed new spark plugs.

    • Meaghan Reimchen

      You are misfiring continue to drive or run with flashing light will cause damage, shut off, wait for about 15 mins and see what happens, if continues, tow to mechanic you trust

  • Ernest

    i do have same syntoms on my car

  • Obia Ranndy

    This tips are 100% correct. I suffered from all these symptoms with my CAMRY and immediately i changed the plugs or even the cable, all went well. Thanks for the tips.

  • Gregory Nash

    yeap helped me off to the tuneup spot.

  • christian tellez

    should I change the seals and even the gaskets since I am there already

    • Inspiredam

      It depends which seals and gaskets you are referring to. On certain vehicles, it sometimes makes good sense to perform additional maintenance at the same time

    • Meaghan Reimchen

      doing the valve cover gaskets will be beneficial if at 200 000 kms

  • sheal

    My car seems like Its going cut off but don’t it shakes a lot what should I do ?

    • Inspiredam

      Does this happen when your idle or moving ? What sort of car are you talking about here?

  • jared

    Hey there ive got 92 318i bmw e36 tht has started a ruff idol and is black smoking a lil bit as well as when im driving it misses and wont go over 5 thousand rpm I have given the spark plugs a clean up and they foul up again and its going through heaps of gas ideas would be a great help cheers

    • Meaghan Reimchen

      sounds like you have a valve issue going on our running rich

  • kene Okoye

    Have got an suv ml320, moves fine at first(engine cool). But engine hesitates/sluggish when hot, i.e, after quite some miles. Please, what could be the cause?

  • Nancy Xg

    I just took my car to get it smoged. I went to two places both said it could stay at 12pmh should I get themChanged. Do u think its the spark plugs
    Help please

    • Nancy Xg

      Oops I meant “It couldnt”

  • Will

    My engine makes a weird noise, and feels like it doesn’t want to go. When I go uphill, the noise doesn’t get louder, the dash lights go out for a split second. One mechanic days alternator, the other says it’s probably my cars “brain” is fried. I’m so confused. Is it just my spark plugs? HELP!!!

    • Inspiredam

      could also be a fuel system prblem, but unlikely to be the spark plugs. What sort of car is it and is the check engine light on ? prbably best to get a diagnostic scan done

      • Will

        84 Cadillac Seville. No check engine light… Got my alternator tested and it went 3 for 3 so all that is good. Not sure what else it could be. It mostly sputters when I start accelerating, then when it goes into the next gear. Tranny fluid is right where it should be and oil too

        • Inspiredam

          I just re-read your post and realized the comment regarding the dash lights going out. I cant think of what would be causing that

    • Boyd

      I had a problem like that as well in my 2001 truck. I would check your fuel filter. My truck was chugging when I would accelerate, loose power going up hills, and lights would flicker on the dash. Hope this helps out.

  • Edward Capers

    My car battery keeps dying. I changed the alternator and got a stronger battery and my car still ends up dead the next day. Could the spark plugs be the problem?

    • Meaghan Reimchen

      probably have a grounding issue

  • Charles Jackson

    Yes, I completely agree that spark plugs are integral part of every vehicle. Replacing your spark plug with a wrong one can cause huge danger. Many of my friends used to change the spark plugs by themselves. But I don’t think that it is secure. I prefer any experienced mechanic or professional auto service center for handling such repairs on my car. Anyway, thank you so much for sharing this.

  • albert

    I have 03 chevy silverado when i put it in drive it wont go any faster than 30mph i have to put it in 2nd gear for it to go the regular speed any idea why it is doing this??

    • Austin McClary

      Sounds like your input or output speed sensor. I would take it to a mechanic to further diagnose it.

    • Tori B

      Catalytic converter.

  • christine

    can anybody help me please.. yesterday id just started driving my car when the steering started juddering quite badly.. I stopped and could smell burning and then the engine management light came on.. I drove the short distance back home and turned off the engine. I had let the oil get low but hadn’t had a signal from my car that my oil was low.. I thought this must be the problem but have since put oil in. when I started the car up it was still juddering and the engine management light is still coming straight on.. its not flashing its on constant. im so worried and don’t have anybody to help.. please could somebody give me some advice?

    • Meaghan Reimchen

      do you have coolant in your car? More than likely overheated

  • damien

    Great article. Changing your spark plugs is vital to keeping a healthy car. A few years ago I used to go over 50,000 miles without changing spark plugs, im sure I only got them changed when the car was misfiring but since then I learnt a valuable lesson and now change them when there due. I keep a record of all the work I personally do on my website and im hoping to teach new comers on how they can save money repairing there car on there own. It’s people like you that inspired me to do. Considering last month I couldn’t even replace a head light, I think ive come a long way.

    please check out my site and let me know if im heading in the right direction


  • albert


    • Meaghan Reimchen

      probably be the starter. Does it click or no?

  • Cotton Watts

    mechanics these days are crooks….i dont trust none of them. ths mechanic in garland tx name Charlie Reeves is the biggest crook of all time. he calls himself the honest mechanic. he will talk very professional over the phone until he gets your car and then he stops answering your calls and he lies and say your car needs this and that…..he tries to talk about God and thats how he gets you. if i ever see that ngga again i’m gonna break his jaw

  • Sophia

    My 06 scion tc is running at a constant 500 rpm … i just changed the throttle body and then throttle body sensor n the maf sensor (twice) n cleaned it with the maf sensor cleaner n it ran just fine till the other day … i drove my car a mile or 2 dwn the road it was just fine then my car sat for awhile and when i took off i try to speed up but it acts like it wants to cut off
    I had to drive my car in gear 1 n 2 all the way back home and all of a sudden my car starts to drive just fine n then do it all over again … help my fix mybcar

    • Meaghan Reimchen

      did you drive it right after you cleaned the throttle body?

      • Sophia

        No i let it sit and run for a a few minute. But I figured out the problem, it was my mass airflow sensor … the guy the SUPPOSEDLY fixed my car, he had put a used sensor on it, which caused it to sruggle to drive off and rpm crazy … but ever sinced i changed it, its been great no problems, the only thing is my car is still idling at 500 rpm cant figure out y

  • Alaskan

    My car shakes briefly after shutting it off. Could this be because of the spark plugs? Its an 89 ford festiva

  • Fernando Ramirez

    The gas accelerater is not working it said engine failsafe mode is a king ranch ford 2005 1500 any recondomandations

    • Meaghan Reimchen

      oh shit! dude you need to take to a dealer or shop to get it off of limp mode! Something seriously wrong with your PCM/EGR

  • Bill

    my lexus 95 was driving fine, till they talked me into changing them. Now is hesitates when going slowly up my driveway, and the engine light is now on…What should I do next?

    • Cali NhC

      did you find the problem as far as the jerking when going up the driveway? i have a 06 gs300 and its currently doing that. i wanna have an understanding before taking it to the mechanic.

  • Bill

    how much does it cost to change spark plugs

    • Meaghan Reimchen

      do yourself is so much cheaper than getting a mechanic.. wires are twice as cheap than stupid dealer

  • Gail Lemaster Thurman

    I was told I need new spark plugs, but is it true that the cost depends on how hard the spark plugs are to reach? I have a 1999 Oldsmobile Delta 88 LS. What is a fair price?

    • mk

      With spark plugs always check your manual period!. Never use other brand than recommended. Spark plugs should not cost more than a couple of dollars. Most regular parts store are OK to go to.Check your manual.

  • http://myanimelist.net/profile/s0ck esodrevo

    01 mustang starts jerking at 40-50mph at 1500 rpm. And it doesn’t consistently if I keep the rpms at 1.5k I usually step on the gas and the rpms shoot to 2k and start driving normally again. Wonder what it could be.

  • krs

    i have a question in regards to the signs of spark plug changing…i was told by diagnostic mechanic testing that the cam shaft sensors was the problem wih my car jerking/hestiation motiion…after changing them the car is starting to do it again! could it still be the spark plugs?! i had two mechanic tell me this BEFORE i let the diagostics done….

    • Meaghan Reimchen

      sounds like a misfire

  • Alisha Nicole Poland

    I have a 97 Ford expedition with 160K on it. I bought it last May and it ran great. Took it from Tennessee to California and on the way i had a spark plug blow. a mechanic replaced all eight plugs and a new coil pack for the one that blew. a month later my truck developed a shudder and when i had my codes ran at Auto Zone they said the code was P0304 (a cylinder 4 misfire) i took the truck to a mechanic and he replaced the spark plug and coil pack. now just a few months later its misfiring again. Not sure what is causing this? And i cant afford to keep replacing them every month or so. Any suggestions to whats causing it?

    • mk

      I don’t understand what “Spark Plug Blow Means?” Coil almost never need replacement. Any way at this point I would replace the EGR valve about $99 and the Oxygen sensor, about $55.00

  • Ashley

    Have a 2002 Bravada and it doesn’t speed up right away and now when I start it, the rpms and battery voltage thing goes up and down. It is OK when I’m accelerating but when I stop and whole car jumps and it’s like it WA ts to lose power. Could it be the spark plugs and if so has it already caused a lot of damage.#

    • Meaghan Reimchen

      have you checked your battery terminals and battery for age, they are only good for a few years and replace, corrosion can cause battery voltage issues. Have you got a code on your car? (check engine or Service engine)

      • Meaghan Reimchen

        check coils too

  • mk

    I have 1990 Jeep Wrangler 4cyl. 125 thousand miles 25 years old. I encountered the same problem and it took some doing to correct.
    The good news is that there are parts available for this year model jeep, and second, it all required very little labor to achieve the “Fix”.
    First off I had issue with knocking valves when starting specially in very cold weather.
    Fix: Drained oil and changed oil and oil filter THIS WAY. 3 1/4 Quart of 5w30 oil, (not 10w40) and one Quart of RIZLONE OIL . (Jeep takes exactly 4 1/4 Quarts of oil including the oil filter.) Knocking stopped instantly when starting in very cold weather. Next oil change in cold weather, always 5w30 oil. (Hot weather 10w40 oil)
    Next issue was rough idle .
    Fix: I replaced the EGR valve. That took care of most of rough idle and amazing speed power in all gears. However it still idled (less) rough and it was “Hiccuping” or (Misfiring)at 40 50 and 60 miles per hour. At this point I changed the OXYGEN SENSOR. This ALMOST completely eliminating the rough idle and NO MORE HICCUPS.
    Next I changed the spark plugs,spark plug wired rotor and distributor cap.
    It runs perfect now. The big expense was the EGR Valve $99 and OXYGEN sensor $55.
    I hope this helps.
    E mail me. manny

  • Bradley Bright

    I have a 1997 Chrysler Sebring Jx Convertible with 150k miles on it, and for as long as I can remember sometimes my car would cut off and I would have to crank it back up before leaving home/wherever I was. My engine would cut off every once in a while for a split second while driving and continue again no problem, always rode smoothly besides that. As for idle, rarely would shake at an idle. My issue is on my way home yesterday from college I completely lost my ability to accelerate and started losing speed, pulled over and my car cut off. After that it would crank up but shake violently and then cut off. Now when I started loosing speed (with my foot on the petal) I could see and hear my RPMs going up but no speed whats so ever. It is currently in the shop getting looked at. At first they said they thought it was my alternator, but after getting it cranked up they said it may be my spark plugs. What do you guys think. Does this sound normal for a spark plug?

    • Meaghan Reimchen

      might be a compression test, or low oil. do you check it often? Also could be MAF problem mass air flow. can also make you stall

  • Nic Robinson

    I have a 1978 Ford high boy it had the rough idle then one day I went to go fire it up it ran for a bit then it had a spit pop out the carb and died and now it won’t even fire with starting fluid would the be the sparkies or distributer or just a bad carb??

  • Jeffery

    I changed 5 spark plugs because my car shakes a bit or it shakes when i accelerate and when i make a stop it also shakes. But its a small shake that you kinda notice, then, now my sports car doesnt have a nice sound like a sports car should sound, it now sounds a bit rough but again i thought it was the spark plugs and i changed 5 and i say it made no difference or im not sure tbh anyways any suggestions? If i add that last 6th spark plug will it make a BIG DIFFRENCE?

  • Emily

    I have a 2008 Ford F-150 my truck starts to jerk when coming to a stop or at a slow speed in the parking lot. I already had a tune up to see if it would fix the problem but the problem still exists. Someone please point me to what I should get a quote for to fix it. Thanks in advance!

    • Meaghan Reimchen

      blow it up, its ford, we had a 2013 fords currently in possible law suit against Ford Motor Co

    • Cali NhC

      did you fix the jerking in vehicle because my car is currently doing the same thing. thanks

  • Anders

    I have a 95 cadillac eldorado and it sort of jumps up and down 2-300 rpm`s at low speed.Spark plugs?

  • Angel Ramirez

    how do you know what is number one spark plugs on bmw 2003

  • Jesse M

    is this the reason why the rpm on my car goes down to 500 rpms and the air filter vibrates also?

  • IMOfuckurthoughts

    this what was wrong with my

    1984 Cadillac Eldorado

  • Mike Emert

    So I have narrowed it down too 1 of 3 problems and hopefully it is the first. I think and hope it may be the spark plug wires because I changed the plugs back in Feb of this year. I have a 97 Acura TL. When in Idle it struggles and RPMS fluctuate up and down and has only gone so low twice to shut off. It struggles to want to go and feels like it’s mis-firing, usually when driving it will clear up and go, but still have the idle fluctuation when at a red light or other times won’t. I have a small oil leak and have tried to maintain it by cleaning the manifold regularly until I can put it in the shop to have the gasket cover replaced (which is what I determined is where the leak is. Real back on the right side) Any suggestions on what to look for?

    Granted the reason I am leaning to number 1 is because the number 2 wire (3rd going from right to left) has slightly deteriorated and sits higher than the other 3 and when I pulled them up looked had particles on it. So I cleaned them off with a rag.

    Determined it’s one of these:
    1) Bad wires
    2) Fuel Injector
    3) Fuel pump