So is the spark plug gap supposed to be 1/2 inch???

[GTSnake]

I was having a hard time starting my car so I decided to pull the plugs. I found some with carbon build up and some that look really clean. Until I got to the no. 7 cylinder. Then I find this:

I wonder how long it's been running on 9 cylinders? Is this a symptom or the cause of some detonation?

I recall my exhaust always smelling a little rich all the time. I just figured it was because of the supercharger requiring more fuel. So does that mean the PCM has been thinking it's running too rich and tries to lean out?

 

[Russ M]

There are many reasons why a spark plug can get hurt. Without a much closer picture of the plug, there is no way to tell you what the reason was.

Most likely its detonation, the reason is because your fuel/ignition management is lacking.

Is that plug covered with oil? If so than the plug is the last of your concern.

 

[GTSnake]

Yeah, it was pretty dark. I wouldn't say covered with oil but just a lot of carbon. I tried to make the picture bigger but I think I need some help.

 

[GTSnake]

How's this?

 

[Daniel Cragin/DC Performance Inc]

This plug shows clear signs of detonation. Do a compression test and make sure this cylinder is ok. The heat range of this plug may not be correct as the insulator is very long. I suggest you dyno the car and check the timing control while listening for detonation.

 

[Bob D]

That plug looks like a stock champion. You should be running something colder.

 

[GTSnake]

It is a stock plug. I was planning on changing to a colder plug.

Dan, I do hear some knocking when I accelerate. But I'm running 6 degrees of retard. How else can I prevent detonation?

 

[Russ M]

Does this car have a vec 2 on it? Who tuned it?

That cylinder looks done, that looks like it is buring oil when it actualy fired.

Detonation is bad VERY bad, when you hear it you instantly let off the gas pedal and fix it. If you dont parts start to go boom, makes no difference how good your parts are detonation will make them junk.

Now what is your next plan of action? Find out if the cylinder is still good.

 

[Sean Roe]

Hi GTSnake,

With the mods in your signature, you should be using the standard plugs enclosed with the SC kit (Bosch FR8DC, part #7527). The ONLY way I'd use stock plugs with those mods is if I had water / methanol injection. You should also at least try the 9D card if you hear pinging.

I'd suggest, as others have, doing a compression test and putting in the colder plugs. Furthermore, consider getting a wideband air / fuel meter (Innovate for about $300) or getting to the dyno for a tune with wideband.

I would hope and think your motor is probably ok as I've seen plugs come out of Viper NOS engines at the drag strip missing several plug ends. Thankfully, you have forged pistons.

Let us know if you need further assistance.

Regards,
Sean

 

[GTSnake]

I guess I do have the colder plugs if they are the ones that came with the SC kit. I never changed them after the install.

I'll try the 9-D card but how come it didn't knock before when I first had the SC installed and just now started showing up. Could I possibly have a bad O2 sensor?

 

[Jack B]

All good comments, as a point of reference, the irregularities on the top of the electrode are splatter from your piston. As everyone has said, extended tip plugs have no place in your application. On the other hand they are not the cause of the problem, you have a cylinder that is obviously running lean. I don't believe that #7 is the the usual culprit. You might want to look at the other plugs with a 25-50 power eyepiece and see if there is splatter on the other plugs.

I do disagree with Sean, in a nitrous engine the extended tip plugs can be melted off swiftly without any damage to the engine, in the case of an engine that has seen long term detonation, you cannot just say there is no damage. A compression check may not show all, have someone do a leak-down test - this is just an opinion.