CRACkED SPARK PLUGS

[russells350]

Hi- I have a Pontiac Grand prix 2000 with a V6 3.8 engine with 100,000 miles. About 3 months ago,my check engine light came on. I plugged in my code reader and got a code of 301 ( cylinder # 1 misfire). I went to the garage,and the mechanic checked the spark plug,and found it cracked (a split down the side) He changed the plug, and everything was ok for about 2000 miles - then again another 301 code. This time it was plug # 8. He again changed the plug and also put on a new set of AC delco plug wires. It was ok until about another 2000 miles - you guessed it - another plug (#1)with a hair line split down the side. I am using AC delco 41-101 plugs. This problem is driving me crazy,and nobody can tell me why this is happening. I even spoke to GM mechanics, and they,like all the rest,say they have never ever heard of a problem like this. Also, the car temperature is normal. I sure am hoping you can find an answer to my problem Thank You. Russell.

[matt5112]

there is no plug #8

Is it being overtorqued?

[cerick08GP]

Definitely an odd problem you have. The first thing I would do is change the plugs myself, most mechanics I wouldn’t trust to change my headlight.
Since the problem seems to be hitting most/all your cylinders what I would do is change the front O2 sensor. You are probably running lean, which btw will kill your engine. That being said here are a list of possible causes.
1) lean A/F mixture
2) pre ignition / detonation (this is where having a pic of your plug would have been nice)
3) excessive OR insufficient torque on spark plugs
4) improper gapping technique (they could be breaking them while setting the gap)
5) water hitting the plug (thermal shock)
6) spark plug heat range to high (this has nothing to do with your engine temperature)
Honestly, first fire your mechanic. Then I’d SeaFoam the engine then install AL606 (or maybe 605) plugs with a new O2 sensor and I’d bet you will be golden.

[SlowNA06]

I'm gonna say that Autolite coppers would be a poor choice for a guy that doesn't change his own plugs. Go expensive, maybe Autolite XP606 Iridium fine wire plug. That would rule out poor gapping, too.

[Warbeaver]

i had an ngk crack on me a while after putting them in. it was from overtorquing at an odd angle.