Spark plug

[VNMUS03]

Just a quick question. My car idles low and good but it has a slight stumble, I guess people are use to seeing that in Cobras. It's stock with the exception of
Cat less pro chamber, stingers, and jlt ram air. I have the platinum motor craft plugs in now but I'm looking to change them.(30k miles on them). I want to pulley my car soon with a 2.8 or 2.93 and I know I'll need spark plugs. I want to avoid buying them now and again then so what should I do. Can I run the ngk tr6 iridium now as it sits?

 

[Bdubbs]

You might be due with a plug change at 30k miles, that could be some of your stumbles. LOL I've probably changed mine 5-6 times in the last 5 years/ 6k miles. How soon do you plan on swapping pulleys? If you want just try the tr6ix's with the gap they come with out of the box. I believe it's around .035 and that should work with a smaller pulley blower.

 

[VNMUS03]

You might be due with a plug change at 30k miles, that could be some of your stumbles. LOL I've probably changed mine 5-6 times in the last 5 years/ 6k miles. How soon do you plan on swapping pulleys? If you want just try the tr6ix's with the gap they come with out of the box. I believe it's around .035 and that should work with a smaller pulley blower.

That stumble was there even when I installed them new. What should I gap the iridium tr6 at for a stock pulley? I can just gap them for stock and re gap if I need to after the pulley swap

 

[DSG2003Mach1]

im not entirely sure id bother with the iridium but if you go that route make sure you understand how to gap them properly, you cant gap them like a copper plug or you risk messing up the electrode of an expensive plug

 

[roy_1031]

I was told run a copper plug with these engines

 

[timspony]

I just use the standard $2 TR-6 plugs .... with a 2.8 or 2.93 inch pulley I'd gap them around 0.032" to 0.035"

 

[Bdubbs]

That stumble was there even when I installed them new. What should I gap the iridium tr6 at for a stock pulley? I can just gap them for stock and re gap if I need to after the pulley swap

So you already installed plugs before and the stumble was still present before and after?

 

[VNMUS03]

So you already installed plugs before and the stumble was still present before and after?

Yeah, I used motorcraft plugs. That slight stumble bothers the shut out of me tho lol

 

[MalcolmV8]

I just use the standard $2 TR-6 plugs .... with a 2.8 or 2.93 inch pulley I'd gap them around 0.032" to 0.035"

Yup what he said.

 

[Jensanity]

I'm having a stumble with mine as well. I'm thinking I need to open my gap a bit, but not sure if that's the correct way to go about it?

What are symptoms of a gap being too tight?
Symptoms of gap being too big?

 

[Bdubbs]

I'm having a stumble with mine as well. I'm thinking I need to open my gap a bit, but not sure if that's the correct way to go about it?

What are symptoms of a gap being too tight?
Symptoms of gap being too big?

In my experience too tight of a gap can cause a slight miss at idle and create the exhaust to make a "popping" sound. To big of a gap and you can get spark blowout.

 

[Tractionless1]

TR6IX with 93 oct. TR6 with E85. Both idle without stumble.