Spark plug replacement after 10 years...
Thread Starter
Burning Brakes
Joined: Jul 2004
Posts: 768
Likes: 6
From: Newport Beach, Southern California
Spark plug replacement after 10 years...
My stock TR coupe`98 has 34k miles. Got the car 2 years ago with 20k miles, plugs and wires are originals...did everything on this car except plug and wires.
Any ppl here replaced 10 years old plugs on a c5 ?....Im going to pay a corvette shop here to do it...or should i leave the old ones in till about 50k miles?....car drives like a dream...if it aint broken should i fix it?...your ideeas please!
Any ppl here replaced 10 years old plugs on a c5 ?....Im going to pay a corvette shop here to do it...or should i leave the old ones in till about 50k miles?....car drives like a dream...if it aint broken should i fix it?...your ideeas please!
Melting Slicks
Joined: Mar 2002
Posts: 2,203
Likes: 63
From: Staten Island NY
Its mileage (use) more than time that affects the plugs and wires.
If the car is running fine just leave it. You can go way past 50k miles without any issues.
The plugs and wires are not such a bad job to replace.
If the car is running fine just leave it. You can go way past 50k miles without any issues.
The plugs and wires are not such a bad job to replace.
Melting Slicks
Joined: Aug 2005
Posts: 2,995
Likes: 61
From: Fort Wayne IN
IMHO I'd get them out after all that time. The longer they're in there the harder they'll be to remove. Some recommend the TR55's but I prefer the AC Delco Iridiums. Don't forget the anti sieze on the threads and a little dialetric grease on the inside of the boots. Makes it much easier to remove next time. $.02 deposited.
Le Mans Master
Joined: Dec 2000
Posts: 9,913
Likes: 1,867
From: Hot Springs AR
The only reason you should think about changing the plugs is to make sure they don't sieze in the heads. Unless you've got a misfire to deal with the plugs will be good for 100K miles. Yes, I know there are folks here that couldn't stand to do that, but there are a bunch of us that have run them that far without problems.
Again, if the engine isn't misfiring, the plugs are fine.
HTH, and have a good one,
Mike
Again, if the engine isn't misfiring, the plugs are fine.
HTH, and have a good one,
Mike
Le Mans Master
Joined: Sep 2007
Posts: 7,604
Likes: 8
From: Belleville Il
The "OTHER VIEW" here!! Get them out!! (Unless you like to drive like a little old lady) The computer will pull timing and compensate for crappy plugs. It will "run fine" when in reality it's just running ok and you are loosing performance(and a little mileage) Mine had 55K when I pulled them out ,,and they were really crappy with gaps all over the place (fron the mid .060s to the mid .080s) when the book called for .040 for the new Delco Iridium that I installed (along with new wires)! The difference was remarkable!! When I posted my satisfaction in a thread(Spark plugs,the 100,000 mile myth) I got a response that stated he did a dyno pull before and the read out indicated the ECM was pulling quite a bit of timing out. New plugs and wires and another dyno run regained the timing and a pick up of 10 HP!! Yes you can run them longer,,but it is NOT worth it,,especially with $4 a gallon gas!!
Instructor
Joined: Aug 2007
Posts: 141
Likes: 0
From: Glen Cove New York
IMHO I'd get them out after all that time. The longer they're in there the harder they'll be to remove. Some recommend the TR55's but I prefer the AC Delco Iridiums. Don't forget the anti sieze on the threads and a little dialetric grease on the inside of the boots. Makes it much easier to remove next time. $.02 deposited.
Racer
Joined: Sep 2006
Posts: 280
Likes: 0
Another vote here to change them & I agree that the hardest part of the job is getting the existing wires off the plugs 
.
If you do it yourself, please wear gloves so you don't cut & scrape your hands.
My recommendation is the Delco Iridium plugs and the GMPP red wires.
If you do a search on here for "spark plug replacement", you will find plenty of help.
.If you do it yourself, please wear gloves so you don't cut & scrape your hands.
My recommendation is the Delco Iridium plugs and the GMPP red wires.
If you do a search on here for "spark plug replacement", you will find plenty of help.
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Burning Brakes
Joined: Feb 2005
Posts: 752
Likes: 1
From: Tulsa OK
34K on the clock the will not create any problems for plugs and wires but the age and time is an issue - man that's like 10 years they have been in there! The plugs could sieze into the heads and be a real PIA to get out. The wire insulation and boots could dry out and crack or the boots may be hard to remove from the plugs and coils.
Just because the platinum and iridium plugs can go 100K without issue doesn't mean that they shouldn't ever be removed and checked.
I would pull the plugs and wires and inspect them. If everyhting looks fine put them back in. Apply anti sieze to the plug threads and make it a routine maintenance item to pull andcheck them at least once a year.
Just because the platinum and iridium plugs can go 100K without issue doesn't mean that they shouldn't ever be removed and checked.
I would pull the plugs and wires and inspect them. If everyhting looks fine put them back in. Apply anti sieze to the plug threads and make it a routine maintenance item to pull andcheck them at least once a year.
Drifting
Joined: Nov 2001
Posts: 1,658
Likes: 25
From: Rochester Minnesota
After 10 years, there could easily be galvanic corrosion between the steel plugs and the aluminum heads. Squirt some WD40 or PB Blaster on them and let them sit for a day before taking them out.
Although not in this engine, I've had plugs break off due to corrosion when I've tried to take them out. Not pretty.
Although not in this engine, I've had plugs break off due to corrosion when I've tried to take them out. Not pretty.
Race Director
Joined: Jan 2006
Posts: 10,554
Likes: 33
From: Not on either liberal coast.
Spark plugs will not spoil with age. If the car is running "fine" with no misfire symptoms/codes, it's not necessary to change them...unless you have the burning desire to spend the money to have them done.
Doing them yourself will be a bonding experience with your car and may be less expensive. It gives you DIY confidence. You will however, not have an enjoyable time doing them. You may need to buy some new tools (that where it usually gets more expensive)...but, I like to buy new tools.
The fact that the plugs are the original plugs and in aluminum heads could be an area of concern. You certainly don't want to strip the threads. Use care yourself or have them done professionally. Use anti seize and you're good for another ten years...
http://forums.corvetteforum.com/show....php?t=2151603
Doing them yourself will be a bonding experience with your car and may be less expensive. It gives you DIY confidence. You will however, not have an enjoyable time doing them. You may need to buy some new tools (that where it usually gets more expensive)...but, I like to buy new tools.
The fact that the plugs are the original plugs and in aluminum heads could be an area of concern. You certainly don't want to strip the threads. Use care yourself or have them done professionally. Use anti seize and you're good for another ten years...
http://forums.corvetteforum.com/show....php?t=2151603
Last edited by hotwheels57; Oct 8, 2008 at 01:30 PM.
Thread Starter
Burning Brakes
Joined: Jul 2004
Posts: 768
Likes: 6
From: Newport Beach, Southern California
looks like im gonna do it...ive talked to west coast corvettes today and they said that not to worry about plugs bonding to heads because they have anti-seize on them from factory...he also said that wires might brake trying to pull them off plugs thou....GMPP red wires and iridiums plugs soon!
Tech Contributor
Joined: Jan 2007
Posts: 19,470
Likes: 1,170
From: Dyer, IN
The "OTHER VIEW" here!! Get them out!! (Unless you like to drive like a little old lady) The computer will pull timing and compensate for crappy plugs. It will "run fine" when in reality it's just running ok and you are loosing performance(and a little mileage) Mine had 55K when I pulled them out ,,and they were really crappy with gaps all over the place (fron the mid .060s to the mid .080s) when the book called for .040 for the new Delco Iridium that I installed (along with new wires)! The difference was remarkable!! When I posted my satisfaction in a thread(Spark plugs,the 100,000 mile myth) I got a response that stated he did a dyno pull before and the read out indicated the ECM was pulling quite a bit of timing out. New plugs and wires and another dyno run regained the timing and a pick up of 10 HP!! Yes you can run them longer,,but it is NOT worth it,,especially with $4 a gallon gas!!
Finally, a voice of reason.....
Le Mans Master
Joined: Dec 2000
Posts: 9,913
Likes: 1,867
From: Hot Springs AR
There's a saying in my office: "Anything is possible if you don't know what you're talking about."
The PCM only uses two sensors to modify the ignition and pulse width commands: the knock sensor and the O2 sensors. The computer only pulls timing when knock is detected, and modifies the fuel trims in real time to maintain the O2 set point (which can change depending on throttle request).
What else would it use? As far as power gains with brand new plugs goes, sure, you'll see it, for about a month. Go back to that dyno (if you really care) after 2-3 tanks of gas and see what happens to that gain. It'll be back where it was (within the noise of the dyno measurement).
Plug gaps from the factory are .053. 60 thou is fine, 80 is opening up some. BUT, if the engine isn't misfiring, the plugs are running fine.
To the OP, the factory plugs are still going to come out tight, so be careful (and patient) when you pull them. As others have mentioned, soak them the night before with some penetrating oil, and make sure the engine is STONE COLD. You want to give yourself every opportunity to have them come out easily.
Then, when you put them back in, put a small amount of antisieze on the plug threads.
HTH, and have a good one,
Mike
The PCM only uses two sensors to modify the ignition and pulse width commands: the knock sensor and the O2 sensors. The computer only pulls timing when knock is detected, and modifies the fuel trims in real time to maintain the O2 set point (which can change depending on throttle request).
What else would it use? As far as power gains with brand new plugs goes, sure, you'll see it, for about a month. Go back to that dyno (if you really care) after 2-3 tanks of gas and see what happens to that gain. It'll be back where it was (within the noise of the dyno measurement).
Plug gaps from the factory are .053. 60 thou is fine, 80 is opening up some. BUT, if the engine isn't misfiring, the plugs are running fine.
To the OP, the factory plugs are still going to come out tight, so be careful (and patient) when you pull them. As others have mentioned, soak them the night before with some penetrating oil, and make sure the engine is STONE COLD. You want to give yourself every opportunity to have them come out easily.
Then, when you put them back in, put a small amount of antisieze on the plug threads.
HTH, and have a good one,
Mike
I know a politician who must live by that creed... 
Instructor
Joined: Sep 2003
Posts: 157
Likes: 0
From: alexandria la
I changed my 10 year old spark plugs last moonth and replaced them with NGk TR55 and now my car runs alot smoother. Furthermore, when I changed the plugs I was hoping that they didn't break off in the head. Change your plugs or else you may be sorry later.
Thread Starter
Burning Brakes
Joined: Jul 2004
Posts: 768
Likes: 6
From: Newport Beach, Southern California
UPDATE!
After almost 2 years since my original post and another 10M I have finally changed my plugs and wires... 12 years and 44M on originals.
Installed AC Delco Iridiums gapped at .40 and MSD wires.
wow! Fells like I gained about 10 hp and is soooooo smooth. Simultaneously got 2 brand new K&N cone air filters for my dual intake.
If GM says that plugs are good for 100M don`t know what to believe because mine weren`t...or maybe just the wires were bad?
Visually both plugs and wires looked great...but were not running properly
After almost 2 years since my original post and another 10M I have finally changed my plugs and wires... 12 years and 44M on originals.
Installed AC Delco Iridiums gapped at .40 and MSD wires.
wow! Fells like I gained about 10 hp and is soooooo smooth. Simultaneously got 2 brand new K&N cone air filters for my dual intake.
If GM says that plugs are good for 100M don`t know what to believe because mine weren`t...or maybe just the wires were bad?
Visually both plugs and wires looked great...but were not running properly
Le Mans Master
Joined: Dec 2000
Posts: 9,913
Likes: 1,867
From: Hot Springs AR
Yep, they feel better, but only for about 500 miles or so. There's something about virgin plugs (never felt this with wires unless there was a particular problem with them) that seems to ignite the fuel more easily.
However, after a tank or 2 I've noticed consistently that the car is running back to normal.
Keep a critical eye on the longer term results; it's real easy to get in the mindset that "I did something, it MUST be better."
The good thing that swapping the plugs out after 12 years is you broke the threads loose (I bet some of them squeaked coming apart) before damaging the threads. You should have put a small amount of antisieze on the threads.
Finally, man, drive your car more! 10k miles in 2 years?? C'mon, your baby is begging "let's GO somewhere!" (yes, I have conversations with my rides
)
Have a good one,
Mike
However, after a tank or 2 I've noticed consistently that the car is running back to normal.
Keep a critical eye on the longer term results; it's real easy to get in the mindset that "I did something, it MUST be better."
The good thing that swapping the plugs out after 12 years is you broke the threads loose (I bet some of them squeaked coming apart) before damaging the threads. You should have put a small amount of antisieze on the threads.
Finally, man, drive your car more! 10k miles in 2 years?? C'mon, your baby is begging "let's GO somewhere!" (yes, I have conversations with my rides
)Have a good one,
Mike
Tech Contributor
Joined: May 2008
Posts: 3,100
Likes: 17
From: Somers, CT and Clermont, FL
St. Jude Donor '09-'10-'11-'12-'13-'14-'15-'16
The shop manual says to put a drop of engine oil on the threads, so I doubt that anti-seize was ever applied at the factory.