Loose spark plugs

recently i took my 2001 pontiac on a road trip from minnesota to florida. (as a bit of background, i live and travel on pretty flat terrain, and i am extremely cautious with my driving, and heve never pushed the car to its potential.) but on the trip, when i encountered hilly terrain the car started bogging down going up the hills. on the flats the car seemed to run ok, though it was developing a tick in the head. when i got to florida i took it to a dealer for servicing. they informed me that the spark plugs on cylinders 2, 4 & 6 were loose (not even finger tight), and had been running so hot that they had started to disintegrate. in fact, i have the plugs and a considerable amount of tungsten and porcelain had dissapeared. the shop then did a compression check and found that compression in those cylinders was below 80#. faced with a $3000 engine replacement on a car blue-booked at about $2500, and no time to accomodate the repairs we ended up with a new used car.

however, i still can’t quite understand how the plugs got so loose. i had had a tune-up including plug replacement at my dealer 15,000 miles ago, and i maintain that those plugs had never been properly torqued. the service manager at the dealer which performed the tune-up service for me has told me that the situation must have been caused (solely) by my catalytic converter imploding, and that it’s demise created so much heat in that (rear) head bank that the spark plugs loosened. in his opinion there was no possibility that the plugs had not been properly torqued or that (even if that was the case) that it could have resulted in my situation. however, i fail to understand why, if so much heat had been generated, why that heat had not transferred to other parts of the engine during steady and extended driving, and why my temp gauge (real, not idiot) never registered my engine running hot or overheating.

i’d appreciate any insights others might have on this issue.

I have seen plugs work loose over time, not often but I’ve seen it. Sure they could have been torqued too little, or too much which could strip out the threads in the head. The cat “imploding” heat theory sounds like a good story, but far fetched in my opinion.

Perhaps your dealer service manager has taken some creative writing courses. This sounds like a mechanical version of Mark Twain.

   Ok, let me go out on a limb here and then saw it off behind me.

My guess is that 15,000 miles ago when the shop did your service

1.they DID NOT replace the 3 spark plugs in question.

  1. OR they started to replace them (and loosend them) but forgot to finish the job.

3.OR, maybe they did replace them and just forgot to torque them as you say.

The problem I see with your dealers answer (blameing the implodeing cat. con.) seems pretty ludicrus to me. Uncle Turbo is right. All service managers are required to attend “creative writeing” classes.

If the cat. con. went belly up why did it only affect these 3? The problem you have proveing any of this, is that you don’t have the car anymore, so your service manager can say just about anything he wants, and doesn’t have to prove it.

Re: your temp guage not registering the additional heat.
This is normal as far as any additional heat that may have been generated around the spark plug threads, or the plug seats. This would be very localized and would not show up on your temp guage.
When the spark plugs are tight they use the cylinder heads as “heat sinks” to carry away the excessive combustion chamber temperatures that are imparted to them. Combustion chamber temps. can reach 1300 to 1500 degrees F. as opposed to 200 220 degrees F for the cylinder heads(coolant temp.) Since these 3 were loose (no heat sink available) this undoubtedly caused excessive wear of the plugs.