Replacing spark plugs - Corolla 03 VVTI (I’m a newbie!)

Hello everyone!

This is my first post I’m making on Car Talk! I’m just messaging in for some assistance as to whether you guys think I’d be able to change some spark plugs for my partners car.

We went to a mechanic a few days ago cause her car has been idling extremely clunky, similar to what a V8 with a crazy cam would feel like and also the acceleration is really bad. You’ll plant your foot down and it would feel as though the power just isn’t hitting the floor at all. I was going up a hill with Over Drive on with the pedal to the floor and I was only reaching 40km, no further than that. Now, even on a flat surface, upon take off usually in the rev range of 0-2k it really shudders and doesn’t accelerate very well at all.

The mechanic we went to topped us up with NZ 98 octane and put some fluid transmission in and it sort of fixed the problem but it came back. They noted the car needs a service for sure and the spark plugs need replacing but the service can’t take place till mid Jan 2018.

I was thinking, without one inch of mechanic knowledge, could I change the plugs myself? I’ve read about it and watched videos and it doesn’t seem toooooo hard but I really don’t want to destroy the vehicle if I do something wrong. I have zero tools
so I’m gonna go out and buy some with my credit card (Happy Holidays!!!) and get to work.

What do you guys think I need? Can you guys provide me with whatever tips or general information you think I need or just wave a red flag and send me to another mechanic to do it.

I’ve always loved cars but have never done anything about it but now, I’ve been listening to Car Talks podcasts (which are soooo funny), learning about the basics of an engine and my now mechanical inspiration has really kicked up!

Please help!!!

Review video and determine yourself

1 Like

If the original plugs are in the car, they are now about 13 years old.
Without any mechanical knowledge, you should consider 1) how you would know if something is about to go wrong (like the coil on plug being stuck or the plug being stuck), 2) how to prevent it from going wrong, and 3) what to do if something does go wrong (like something breaks while trying to remove it).

If you choose to proceed, do you have a friend with more experience who can help you?


Good video from @MikeInNH & comments from @Waterbuff. Replacing the plugs on this car is pretty easy for someone with a bit of experience. But without the right tools you can mess it up. Once the plugs are exposed after the coil is removed, use compressed air to blow out any dirt. The coil covers the plug nicely but there still could be some junk down there. After blowing it out, spray a bit of PB Blaster (Walmart-Advance Auto etc) and let is soak for an hour. Then gently put a socket on the plugs and unscrew them. The new plugs should be Denso brand, that is the OEM Toyota uses. I got mine from the dealer at about the same price the auto parts stores was selling what they called equilivant. Toyota’s are fussy about their plugs, Denso’s are great. When you put the new plugs in make sure they are lined up, don’t use the wrench to start them. You will need an extension on your socket wrench, use your fingers on the extension to start. Once you have them in a few turns you can start with the socket

1 Like

I have mixed emotions. While I far prefer to change my own plugs and truth nobody else not to cross-thread or overtorque my plugs, I’ve seen enough newbies mess even this simply task up to be wary.

It’s an easy job, and a good one for someone mechanically inclined with a desire to learn about engines, but it might not be a good idea for someone with zero aptitude and no desire to do anything beyond changing plugs. Besides, what will you do if a plug is stuck?

In your case I’d recommend finding a reputable independently owned and operated shop and letting them do a diagnosis in addition to changing the plugs. Tell them the symptoms, tell them they’re the original plugs, and let them work their magic.

Besides, if you screw the job up think of how your “partner” will feel. It’d be risky to do it yourself.

1 Like

Your problem may not be the plugs. Do you know just how old the plugs are? If you don’t have the maintenance history on the vehicle, then you won’t be able to find out, unless you know the former owner always had their dealership do the maintenance. Then the maintenance history will be available at any Toyota dealership.

Is the check engine light on? If it is, then you need to have the DTC (diagnostic trouble code) read. In most states, you can get them read for free at most car parts stores. If the light is on and you get them read at a parts store, be sure to get the alpha-numeric code to post here. It will be a P followed by 4 numbers. For example P0303. This is important as the parts place will tell you something like misfire, replace plugs.

They usually enter the code at their computer and it spits out the result on a cash register receipt with the problem and all the things you can buy to fix the problem. The code will be at the top of this receipt. We don’t want their opinion, just the code, you will get a better insight here with that.

Be sure to tell us whether you’re friend has owned this vehicle since new or if it is newly acquired and how many miles are on it. This is important.

One more thing, the transmission dipstick is the one with a spring clip over it. Pull it out and look at the color of the fluid on the tip and let us know. This is also important.

1 Like

This is a good suggestion, and if Ben is going to do this, I have a slightly different one:
use a short length of stiff (rubber) tubing/hose on the top of a new spark plug (instead of a socket or extension) to start threading it into the engine. If you start crossthreading the plug, the tubing should slip on the top of the plug before damage occurs.
Once the plug is threaded “in”, pull off the tubing and use a socket to complete the job. Don’t forget about the torque specs.


The only thing I would change on the video is to not have the ratchet on the extension when you start the new spark plugs in so you can feel them thread in by hand. Once you can feel them thread in put the ratchet on to tighten them.
As far as blowing out the hole with compressed air, I am sure you don;t have an air compressor, and I changed plugs for 20 years beofre I got one,


You can buy a can of compressed air at Wallmart


Thanks for this Mike! This is one of the many videos I’ve watched, it makes it look pretty simple!

Hey Keith! We had the people from the dealership we bought the car off have a look and drive and they said it definitely was the spark plugs. She has a mechanical warranty, the car has done around 240,000km and I don’t think the spark plugs are the original. She isn’t the original owner either. Hope this helps

Then let her use it and avoid the problem of you messing something up. You might see if you know someone who does things to their own vehicles that might let you watch and learn for the future.

1 Like

If it has bad plugs, it will have a check engine light and one or more codes in the range P0301 to P0304. If it is P0300, then it may not be the plugs. Also if the check engine light is flashing, it needs to be repaired immediately or it will get a lot more costly, fast.

1 Like

I’m a diyer and have always changed the plugs on my own Corolla myself. It’s an older one, early 90’s, so the procedure is bound to be a little different for a 2003. For me it’s a simple enough job, takes about 20 minutes to change out all four. It’s common sense to secure at least a Haynes or Chilton’s maintenance and repair manual for the car and read through the procedure before starting.

Here’s what you want to avoid at all costs.

  • breaking off a plug while removing it. if you can’t get a plug out easily using the ideas here, don’t force the issue. stop and take the car to a shop.
  • cross threading a plug while installing it. if you aren’t sure, stop and take the car to a shop.
  • dropping anything into the spark plug hole. clean the hole before removing the old plug, then use common sense.
  • overtightening the plug, or not tightening it enough when installing it
  • using the wrong plug part number

First off, I buy the NGK replacement plugs, making sure I’m getting the same part number as is recommended in the owner’s manual. Buy your plugs at a dealership if you have any question about whether the part number is correct. Then I visually inspect each plug for any signs of cracked metal or porcelain, and that they are gapped to spec. Then I take the plugs out to the car, set up a work bench, and pop the hood. Next I remove the plug wires from the plugs. My wires are all of different length so it is clear which plug goes on which wire. To be sure you can number the wires with a marker before removing them. The plugs are down inside a deep hole, so you need an appropriately sized 3/8 inch drive spark plug socket and ratchet to get them out. Spark plug socket are taller than normal sockets usually. Use the type of spark plug socket that has a rubber insulator inside, helps prevent damaging the spark plug. Test the fit of the socket on one of the new spark plugs so you know how it feels when it seats correctly.

It’s a good idea to remove any debris in the holes before you remove the plugs. I just us a shop vacuum cleaner and make my own adapter to fit the hole. Compressed air would work too. To remove a plug, put an extension on the socket (but not ratchet) and hold on to the extensions while you place the socket over the plug to where it is seated. Then install the ratchet and while supporting the extension with your other hand, loosen and remove the plug. The plug may not come out with the socket and be left in the hole, so be prepared with a set of long forceps you can poke down the hole to grab the plug to pull it out. Sometimes the socket will stay down the hole too, and the only thing that comes out is the extension. You can tape the socket to the extension with some duct tape to prevent that.

As each plug comes out, number it with a marker. Take the time to inspect the tips of old plugs, comparing them to photographs you can find on the internet of what used plug tips should look like. Especially take note if one of the plugs looks much different from the others. They should all look more or less the same.

To install a plug, double check it is undamaged and the gap is correct. I apply a very thin layer of moly lube on the threads, but not everyone here agrees on that point. Helps making removal easier the next time. Put the plug in the socket (it will stay there if the socket has that rubber insulator) and attach the extension to the socket. Now carefully place the plug as vertical as possible into the hole. Thread it in by hand, holding only the end of the extension. If it grabs at all, lift it up and try again. It should start to twist into the hole needing with very little force at first. This is done to prevent cross-threading the plug. You should be able to twist it in 1 to 1 1/2 turns by hand using only the extension, after which you’ll need the ratchet. The final job is to tighten the plug to the correct torque spec. Make sure you know what this is for you make/model/year/engine. The safest approach is to use a torque wrench. If you don’t have one, you can estimate the torque using a bathroom scale. Say you want 15 foot pounds. Press on the scale to feel what 15 pounds feels like, then press on the ratchet handle one foot away from the socket with that same force. When all the plugs are in, use a flashlight to make sure the rubber insulator from the socket isn’t still stuck on top of one of them, and that there’s nothing in the hole other than the spark plug.

I always double check the plugs aren’t loose, remain at the right torque, after a week of use.


For a starter tool set, go to Home Depot (Husky), Sears?KMart (Craftsman) or Lowes (Kobalt) and get one with spark plug sockets, etc. The larger the set, cheaper the price per piece, as a general rule. You may be tempted to get a really cheap set somewhere but the ones I mentioned have lifetime warranties. You could also spend a lot more (e.g. Snap-On) but that won’t be necessary for casual, occasional mechanical work.

1 Like

Thanks everyone for all your help. We took the car to the dealership we bought it off and asked if we could get a company car instead, the car was really troublesome - but then I asked if I could maybe change the plugs myself and if it was a hard job and the mechanic told me to bring the car to the back and he actually taught me how to do it myself and we replaced them together! I didn’t do much it was pretty weird trying to use the ratchet thing lol, hard to understand the concept but that’s what you’ll get being a Banker full time zzzzz. Really awesome to see it all in action though, could definitely DIY next time! Thanks again everybody.

I guess you either have interest in DIY or you don’t. You always make mistakes so just be ready for it. When I was 16 I replaced the plugs on our 61 Merc and managed to break the porcelain on a couple by not using/having the right socket. Then my second time on my 59 Pontiac I managed to get 7 in but had to go to the shop for the eighth one. Then after 50 times or so I managed to have a problem getting the boot back on in a tight space. My last plug change was just done by the shop, now that I’m not driving 50K miles a year.

Well, did new plugs solve the problem?

1 Like

Aaaaand the plugs solved the problem and she’s running amazingly!

1 Like

Congratulations on a job well done.
Feels good, doesn’t it?

1 Like