Mechanic error? Thoughts?

[John_Mc]

Hi all. Not sure which is the best forum to post this in. My wife has a 2002 Mazda Protege which she bought new and has meticulously maintained for 9 years. It has run flawlessly for 128,000 miles. She took it in last week for routine service (check fluids, change oil, check belts and tires) at a national-chain service station that she has used for about 6 years. After that the car was idling rough. Tuesday as she was driving it, it got worse and began sputtering, then chugging, then the check engine light came on, and she heard a "flap!flap!flap!flap!...". Coincidentally, she was close to the same shop that had done the service work and pulled in there. After checking it, they said the #2 spark plug was stripped in its socket and even looked like the cylinder had pinged against it and that the car would need a new head! They still haven't given us their final diagnoses (I will call them tomorrow). Is this something that could possibly happen on its own or is it overly likely that something done during the service visit caused this? Thanks for your insight!

 

[racingenglishcars]

It's possible the spark plug wasn't tightened properly. It could work its way loose and cause the stripped threads.

An easy repair for that is a spark plug thread insert. Commonly used on old Beetles, they have been available for centuries just so you don't have to replace an aluminum head when the spark plug threads strip. They can be installed without removing the head.

examples:
https://www.locknstitch.com/sparkpluginserts.htm
https://www.popularmechanics.com/cars/how-to/repair/4212608

Google "spark plug insert"

 

[John_Mc]

Thanks Donn, I will pursue that route. Is there no concern of metal fragments in the cylinder after such failure and subsequent repair?

 

[DrEntropy]

It must be done carefully. An insert procedure can drop swarf into the chamber.

If the head is off the deed is MUCH less endangering to rings and valves. Err on the side of caution is my opinion.

And if that same shop has been the "primary caregivers" to the vehicle, I'd find another bunch to do the job. How would a plug hole be mangled other than when THEY changed it?

Just my silly observation.

 

[NutmegCT]

My two cents: have we established that the shop actually did remove the plugs?

It was taken in for "routine service: check fluids, change oil, check belts and tires". Did the invoice and/or mechanic refer to checking the plugs?

Would be interesting if the damage was done when they did *unauthorized* service.

T.

 

[elrey]

Good question. On the other hand many times stuff will go wrong right after it leaves the shop that has no relation to the work done. Seen that plenty. Some kinda law at work there. Someone somewhere did something to have this happen, just not necessarily the very last folks to work on it. [But probably] The rough idle is a good clue that the problem occurred at the shop. The plug could have been cross threaded by a ham handed tech, and/or not tightened properly as has been pointed out. Many times a tech has cross threaded a plug, realized it, and then gently put the plug back in with his fingers crossed. Aluminum heads are sensitive to such treatment. Offhand I'd go with Doc's concept though it will cost more in the short run.

 

[elrey]

Furthermore, you may wish to check the service interval on the water pump and timing belt and, if necessary, have them done at the same time. Hopefully you will get satisfaction from the shop on the plug issue.

 

[JPSmit]

I'd also be following up the cylinder "pinging" could be damage there certainly out of balance.

 

[jessebogan]

Snap on makes a "cheap" bore o scope. They are in the $350.00 range. Shop might have already... Have a look insige the chamber, It is possible that there is FOD... Tech might have misplaced nut, bolt, tool etc when changing filter, and it made its way into the chamber, with the subsequent horrer show. If no scope, then pulling the head is the way to go. I concur with timing belt, rollers, and so on. Make sure you SEE the damaged plug, and the inside of the engine, whether thru a scope or after disassembly.

 

[Banjo]

The one piece of info that makes me wonder is the statement that "The piston may have pinged of it" There is no way the piston EVER would have hit the plug unless,1, the wrong plug was installed with far too much reach (But that would have been noticed immediatly) or 2,there was some foreign object in the cylinder that hit the plug, like a nut or bolt or some such.
Hmmm.....

 

[jessebogan]

Exactly. There should NEVER be any thing inside the combustion chamber that could actually damage anything, let alone a spark plug. My great fear on reading that is a bolt perhaps forced the plug out. So a very careful and detailed inspection is called for here. As the customer, you should ask to see any damage, including the spark plug. Take some pics and post them here if possible, and the group mind here will help you with the best course of action to take. I REALLYT want a look inside.

 

[elrey]

One would think that anything big and strong enough to push a spark plug hard enough to strip the threads in the head would surely cause further destruction [valve, piston, cylinder wall]. I have seen rotted smog exhaust recirc. components release their guts directly into the intake manifold and ruin things in a big way.
Sometimes the inside end of the plug gives up for various reasons [impact by a foreign object being one of them] and creates trouble... There is certainly more to this story.

 

[swift6]

Do the little Mazda engines, aluminum heads, suffer any of the same habits of ejecting spark plugs like some of the aluminum head V8 Ford engines. The Tritons have a particular habit of it. Ford claims one of the causes for this is over-torqued sparkplugs following a service. However I have seen it on factory installed plugs on high mileage engines as well. What typically happens is that the threads strip, the plug gets loose (rough running) and then pop, out comes the plug.

 

[NutmegCT]

"They still haven't given us their final diagnoses (I will call them tomorrow)."

John - what did you learn when you called them?

By the way, when you said the car was taken to a "service station", did you mean a gas station? Or something like Midas Muffler, or Sears Auto, or local mechanic, or Mazda dealership, or ...? I'm an old guy, and "service station" to me means a national or regional gas station - not where I'd likely go for regularly scheduled Mazda maintenance.

Thanks.
Tom

 

[elrey]

That's the happiest scenario, the ill applied plug that works itself against the soft aluminum threads in the head till it is free. My fingers have been crossed in that direction. We can but wait and hope.

 

[NutmegCT]

So John ... what's the verdict?

What did you learn when you talked with them at the shop?

Tom

 

[elrey]

WHAZZUP?

 

[Guest]

A detailed explanation of the services that were performed would have to be provided to see if the problem could have been caused by mechanic error. Im very leery of national chains,because their mechanics are paid a commission on the services they push,regardless if they are needed. As for the 5.4 ford plug problem showing up in Mazdas,the answer is no. Kind of weird how the problem seems internal to damage the plug in that manner. Someone drop a screw or bolt into the plenum changing an air filter and it got sucked into the cylinder? A stripped plug hole is easily fixed with a helicoil set. Something smacking around in the cylinder could easily ruin the head. Get the car out of there immidiately and to another shop. I think you will end up paying for what they did wrong.

 

[NutmegCT]

John_Mc - what's up?

What did you learn about the problem?

Tom

 

[John_Mc]

Wow! I didn't realize so many people had responded to this thread! I posted it, saw the first two or three replies and then took the car in to a reputable shop for repairs. Sorry I didn't follow up with you guys. I really appreciate all of your input. The shop in question is a national chain like Midas (but not Midas). I hate to name names since I don't think you can necessarily blame the chain for the work of an individual. They wouldn't own up to having caused a problem, so I took the car to a foreign car shop recommended by a friend. They were able to use the helicoil method to fix the car and it has run fine since. I don't know if they looked inside or not. They didn't indicate any internal damage or foreign object, so I think the idea of a poorly threaded plug makes sense. Let's hope this fix is good for another 100k miles. Thanks again for all your replies! Next time I'll try not to "post and ditch"!