1997 cracking spark plugs

About 5 months ago I replaced the spark plugs and everything was working great. 2 weeks ago I developed a misfire on number 4. When I pulled the plug it had a crack going up the side. I thought maybe I cracked it on install so I went and bought another. The car ran good for maybe one day then misfire again. So there I was doubting myself thinking I cracked it again on install and replaced another. Anyway, three plugs three cracked. Now on the fourth and made sure I didn't do anything to crack it. Anyone ever come across something like this. By the way the car is a 1997 gtp with almost 280,000 on it. One other thing, when I turn on the blower motor on speeds 1-4 the motor cuts out and comes back on. When the motor cuts out the information center also shuts off and doesn't come back on until the blower starts again. Thanks for any help.

What type of plugs are you using? have you done any modifications to your car? (smaller pulley)

plugs are ac iridiums and the only mod i have done is the 3.4 pulley

What brand plug wires are you using? Why are you using AC Delco Iridiums with a 3.4" pulley? Is it the AC Delco 41-101? You should drop to a colder plug (one range) or at least check knock retard (KR) to see where it is at.

I've never heard of the AC Delco Iridiums cracking or getting carbon tracks on the ceramic but it is a common problem on certain AC Delco plugs like the Rapidfire 14 so a manufacturing defect is a possibility.

What plug would you recomend, the pulley has been on for at least two years now and this is the first time this happened.

Autolite Copper Core 605 (one colder) or 104 (two colder) or colder AC Delco Double Platinums listed at our Tips & Maintenance forum. Another option would be NGK plugs since they have different heat ranges available.

Are the plugs cracking internally around the center electrode, or externally where the plug boot slips over?

The blower motor and DIC issues are a sign of the ignition switch harness contacts starting to arc. A common issue on these cars, again mentioned with replacement proceedures in the "tips and maintenance" subforum.

The plugs are cracking around where the boot slips over. So far all the way up the ceramic.

Do you see any black carbon in the cracks? Carbon tracks. Also, are these big cracks or just hairline where you have to look very closely.

these is a hairline crack. a little hard to see. as far as the carbon, it looks like that is what is inside the crack

It sounds like you have a detonation problem due possibly to carbon build-up or a lean air/fuel ratio in that cylinder. Have you checked the color of the plug when you pull them out, to see if the cracked plug is a different color than the others. A whitish color would indicate a lean condition.

Could be detonation. Nothing a KR check won't reveal. However, since I've seen this with problem specifically with AC Delco plugs I'm voting defective from the manufacturer.

I agree Bob, I was just mentioning the color so he'd have something else to look at since it's only happening on that one cylinder. It's one of those things you sometimes don't think to check when frustrated and working on your own car.

Just in case there are any disbelievers about the quality of AC Delco spark plugs in reference to the ceramic cracking here is a pic of an AC Delco Platinum Rapidfire 14 which is one recommended replacement plug for the na and supercharged SII 3800 engine. These failed within 3K miles of installation and showed a blinking SES/CEL light (misfire) and DTC at the respective cylinder. Replaced under warranty and Autozone exchange policy for Autolite APP 606 which are long life dual platinums. No problems since the AC Delcos were replaced.

http://i5.photobucket.com/albums/y186/lizzywiz/acdelco_crack.jpg
AC Delco Platinum Rapidfire 14 with hairline ceramic cracking visible and carbon track

I've never liked Rapidfires either Bob. They are another version of a gimmicky plug that doens't live up to any of it's claims. They are actually inferior to the OEM plugs, so it's a negative no matter how you look at at them (except that they are cheaper cost wise than the AC-Delco Iridiums). I also believe Autolite double platinums are a high quality alternative to the OEM's.

I've never liked Rapidfires either Bob. They are another version of a gimmicky plug that doens't live up to any of it's claims. They are actually inferior to the OEM plugs, so it's a negative no matter how you look at at them (except that they are cheaper cost wise than the AC-Delco Iridiums). I also believe Autolite double platinums are a high quality alternative to the OEM's.

:lol:

I hate them and I agree do not match the specs of the OEM plugs which were double platinum. And I'm beginning to distrust any AC Delco spark plug other than the real originals if you can still find them like the OEM double platinum 41-921 or NGK Laser PTR4B-15. Many GTPs were delivered with the latter NGKs. The problem with the 41-101 Iridiums is they have the redesigned ceramic and are actually for a wide variety of GM engines and lord knows what the colder plugs are. :confused:

On the Autolite brand definitely the choice of owners with modded GTPs since copper core are better racing spark plugs. And of course, easy to remember numbering system for the alternative heat ranges. For the OP if Autolite double platinums are considered just use the AL APP605 which is one range colder. The major difference between the Autolite plugs is the life. The copper core do not last as long as the platinums.

Lately another favorite is the NGK TR55IX Iridium. Best part is the user can safely adjust the electrode gap to compensate for smaller SC pulleys and other mods. Cost is good depending on where you buy them. NGK TR6-IX Iridium spark plugs is the next range colder.

The 41-101's were originally a direct replacement for the 41-921. Lately, I've seen them sneaking onto other GM engines like the 3100 and 3400. This gives them less overhead for OEM parts and plants can trade stock if necessary.

I know this is kind of late, but what did you find out was going on? I'm having the same problem except in cylinder 1. I swaped the plugs about 4-5 months ago and have been having this problem for about a month now. I thought the first 2 that cracked were maybe coincidence, but it hasn't stopped.