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The Spark Plug Shot Out Like A Rocket


I took my 2003 Toyota Matrix with around 148K miles to a local shop for the 150K work. This is the first time I have not taken it to the Toyota dealership because I wanted to use a local shop that works on Toyotas. I live in Asheville, NC. I spent over $800 for this service, rotating and alignment, plugs changed etc and they checked a engine light and told me I needed a new catalytic converter.

I took the car in on November 2nd. On December 23rd I was driving on the interstate and heard a pop and a coughing noise. I was stranded on the side of the highway in Knoxville, TN.

I got a tow to the a Toyota dealership where I learned that “the spark plug shot out like a rocket” through the header. I ended up getting a used motor for $4400.

I have since spoken with other mechanics, all who have said that this is a problem with Fords. All have said the plug must not have been installed properly. They said it could have been a faulty plug but they don?t know how.

Here is my question:

My buddies tell me I should approach the local shop and tell them what happened. They tell me that I won?t get anywhere or any compensation but I should let them know.

Have you heard of this with Toyota?s?

Would you talk to the local shop?


Lady and Dog on side of highway

I’ve heard of spark plugs blowing out for some reason or another. But I’ve never heard of a case where this required replacement of the engine. Care to elaborate more on that?


Yes, please do tell how a spark plug blowing out ruined the whole engine.

Tom and Ray have taken several calls over the years from people whose spark plugs blew out. And according to Tom and Ray, the only reason was that the installed didn’t tighten the plugs enough. Eventually they worked loose and got blown out.

It is almost certainly the shop’s fault that your plug blew out. They most likely didn’t tighten it sufficiently. Or they damaged the threads during installation, which is less likely, but still their fault. And if you do in fact need a new engine because of it, all the more reason to complain to them.

I too am on the edge of my seat.

Explaination, you are driving car, all of a sudden a noise, you pull over, open hood, find plug still attached to wire (or coil pack), this is all fine BUT if you were driving with the hood closed how does anyone know if it “shot out like a rocket”?

You could say “look guys, no one knows if the plug shot out like a rocket or fell out like a weeble wobble, that is not the point, all I want to know is if I should go back to the shop that installed the plug and tell them that because of their lousy plug installation techniques I now need a new engine”?

This is usually caused by someone overtightening the spark plugs in aluminum cylinder heads and this is true of any alum. head engine no matter who the car maker is.

This repair does not necessitate a new engine or even a new cylinder head unless there is more to the story.
This ranks right up there with replacing an oil pan because the drain plug threads are stripped out. Possibly.

It happened on my Mazda truck so I bought a good thread repair kit and fixed it in the parking lot before driving home. Not true. My wife drove me home. I took her car to buy the $20 kit went to work and fixed the truck then had her drive me to work the next day. Not true either, I drove. I wish things were always easy.

Given the present situation, I would have a bigger problem with the shop that sold you an entire engine to remedy such an easy to repair problem like this. What is this shop’s reasoning for replacing the engine because a spark plug blew out of a cylinder head? A real shop would repair the threads with a Heli-Coil kit. If they mentioned the possibility of metal shavings getting into the engine, you tell them that’s what grease is for.

As far as why the plug came out in the first place, there are a number of possibilities for a cause. The previous shop may not have sufficiently tightened one of them, they could have overtightened it, cross-threaded it, or someone before could have weakened or damaged the threads during a previous spark plug replacement. Either way, it happened, and I am of the opinion that whoever ordered an engine replacement over this problem was out of line, unless you provide further details that something more happened that could warrant an engine replacement. A spark plug blowing out of the head does not warrant engine replacement.

they checked a engine light and told me I needed a new catalytic converter.

There is no light that tells anyone they need a new catalytic converter. There may be codes that suggest further investigation and might end up with a new converter, but certainly not always.

Get the code read by someone else (many autopart stores will do it for free) and post the code(s) as a reply to your original message.  The code should be in the format [P1234] 

Good Luck

Hopefully I will answer your questions.

According to the Toyota dealership in Alcoa Tennessee the spark plug damaged the cylinder head. They gave me 3 options:

  1. Pull the cylinder head/send it to a machinist to see if it could be fixed for $2600+tax
  2. They didn’t know if it could be fixed so replacement would cost $3434+tax
  3. Get used motor with lower miles and use parts (belts etc)they could with mine for $4400.

I opted for #3

So, my questions remain about the local garage in Asheville, NC
A) Have you ever heard this with Toyota’s? I have heard it is a problem with some Fords.
B) Would you say something to the local garage?

It seems to me that the plug wasn’t installed properly but quite frankly I am a cardiac nurse. I feel very comfortable defibrillating someone but this is out of my league.


Apparently the dealership found that the threads in the aluminum head where the spark plug screws in were damaged. Which means that whoever installed that spark plug damaged the threads in the aluminum head, most likely by over-tightening.

Which means that, yes, you should go back to the local garage in Asheville and tell them what happened. Probably too late to get anything out of them. You should have had them look at the old engine before it was removed, so they could see the threads that they damaged. But at least you should tell them, and possibly prevent them from ruining another customer’s engine.

Furthermore, as others have pointed out, the dealership didn’t do you any favors, either. Most likely it was a simple fix (pleasedodgevan2 did his fix in a parking lot with a $20 kit.) The dealership gave you a list of the 3 most expensive options, any of which they would have made plenty of profit on. Replacing your engine? They made plenty of profit on $4400.

As to your question about Toyotas and Fords, it has nothing to do with the make of the car. It has everything to do with the monkey who installed the spark plug.

Next time someone tells you your car needs an expensive repair, ask here first. And find someone else to work on your car here:

And, by the way, here’s a short article from Popular Mechanics that describes the simple repair someone could/should have done for you:

You are likely the victim of incompetence rather than outright fraud although the end result is the same.

These people should sell their tools and find another line of work. Repairing a spark plug hole is comparatively simple and it does NOT require removal of the cylinder head.

Jesus, you would have thought that one person in that shop or chain of command would have raised their hand and said hey guys, why don’t we just install a Heli-Coil.

This original problem was likely caused by someone who overtightened the spark plugs. The expensive engine replacement problem can only be defined by one word; morons.
What an embarassment to the profession.

As far as the local shop goes, I’d also mention it to them though without the original motor for inspection they’ll have no idea what to make of it. They certainly are not without blame, but it is true that plugs can become nearly welded into the cylinder head if not installed with some antiseize and if left in too long. The head is soft aluminum and the root cause of losing those threads may have been this rather than overtightening. We’ll never know.

But as OK4450 said, the real culprit here is the Toyota dealership that sold you a used engine. It is quite astounding. If I was going to have a talk with anyone, I’d reserve more of my ire for them rather than the shop that did the plugs.

Aside from the probable incompetence of the “mechanic” who fitted the new plugs (if he even did so?) this Toyota Dealership should be reported to the Toyota corporate and the BBB and receive a radical nadectomy. ABSOLUTELY DISGRACEFUL.

I’m in agreement with cigroller about saving your ire for the Toyota dealer. The point could be made the shop performing the plug installation may not even have been responsible for overtightening the plugs.

You reference having all other work done at the Toyota dealer prior to the plug replacement so if the plugs were changed previously by the Toyota dealer they could have been the ones to overtighten them and cause thread damage. The independent shop could simply be the ones looked at as guilty because they were the last one to touch them.

Also in agreement with cigroller’s use of the word “astounding” and the suggestion to fire off a letter to Toyota corporate about this.
I’ve seen absolutely idiotic things done over the years but I think this one takes the prize as to cost and the reason why.
John Dillinger used more tact when robbing a bank.

As a matter of fact, the OP should not only fire off a letter to Toyota but they should also direct Toyota to this discussion.

Any shop is free to set guidelines as to how they would repair damaged threads (or not repair them). It appears this shop does not want any liability in the event that another plug (or even the same plug) blows out again, it is their right to set the policies that they will perform this type of work under.

Perhaps more is going on here than we know. It is very difficult (in fact you really have to try) to damage plug threads when simply installing a plug. Perhaps this plug never accepted the torque when the mechanic installed the plug. You really have to lay some continuous rotation on a plug to strip the threads out. If the guy cross-threaded it, well then it would even be more unlikely to blow out.

The Dealer is saying “we really don’t want to touch this, but if you insist here is how we will do it”. If you don’t like our conditions I will call the tow truck for you.

I am absolutely 100% in league with those who are appalled.

At some point in the engine’s life someone improperly installed at least that sparkplug damaging the threads. My guess is that they overtorqued it, but leaving it loose or crossthreading it are also possibilities.

Nomatter. This is not an uncommon error. It’s common enough that repair kits are sold just to repait stripped spark plug holes. Here are some examples.

And you got a used motor for $4400? I’m appalled. Attached is the cost of a whole remanufactured head! Less than $300 (plus S+H).

I can understand why OK4450 is so appalled. I am too. With the utmost respect, you’ve been “taken to the cleaners” by that Toyota dealer. I’m very sorry.

It’s much easier to strip or cross-thread a plug on modern cars with deep well plugs unless one uses a rubber hose to start the plug with. Most mechanics grab the magnetic plug socket and have at it.

In this case, I did not see a thread repair on the list of options the OP was given but I did see the most basic as being removing the cylinder head and sending it to a machine shop to have done what could be done with the head in place and in the car.
For crying out loud, this is Basic Mechanics 101 and it’s a sad commentary on the shop.

I suppose the dealer could be forgiven if the deepest breadth of their mechanical knowledge is operating a transmission flush machine and a job like this is just clean out of their league.

The point could also be made that if these guys are afraid of performing a spark plug hole repair then what makes them have so much bravado when it comes to pulling the cylinder head off or swapping in a used engine of possibly dubious ancestry?

So much disgust at the Dealer who had nothing to do with the car becomming damaged. I have saved my disgust for the shop that did the deed.