Possible spark plug issue ...

[Leo Rojas]

Hey guys ...

I did a full engine rebuild on my 6 bolt about 3 months ago, using all OEM parts except for COMETIC head gasket and ARP head studs.

I have a GREDDY electronic boost controller set up at Low Boost - 10 psi and High Boost - 15 psi.

I used DENSO Iridium IK24 spark plugs, they worked fine but about a month ago the car began stuttering at 15 psi, at 10 psi the car runs perfect.

I bought a set of NGK V-Power 7 and set the gap to 0.8 mm. With this new plugs the car runs fine at Low Boost but if I do a third or fourth gear pull at High Boost the car begins to stutter, but if I do a second gear pull the car runs strong all the way through fitth gear. It's like it lacks low rpm power ...

This didn't happen when I bought the DENSO Iridium, I could do a third or fourth gear pull and the car would run perfect.

What could be the problem ?

Should I get Denso Iridium again ?

Is IK24 good for me or should I use IK22 ?

I'm not planning on running more than 18 psi on my 16g.

Thanks for your help.

 

[Defiant]

Stay with NGK BPR6ES, unless you find you're burning them up. Use a .028" gap to start with.

DSMs do not like ND plugs, and there's no need to go for fancy ones. They're too easy to change, and iridiums and the like are meant for difficult-maintenance applications.

 

[Leo Rojas]

So the problem could be the gap ...

At this moment my gap is 0.032'' or 0.8 mm.

I'll try 0.028'' and see what happens.

Funny thing, at first the gap was set to 0.024'' or 0.6 mm and at High Boost it was terrible, when we opened them to 0.032'' it was a lot better.

Thanks for the reply.

I'll let you know how it goes

 

[ECLIPSE4x4]

Like Defiant said, go with the NGK BPR6ES, or possibly 7ES.

Gap them to .028 abd you will see the difference.

Also, please fill out your profile info on your car.

 

[Leo Rojas]

No good news ...

I gapped my plugs to 0.028'' and there was no difference.

I think I'm gonna go with the Denso Iridium again. Should I go with IK24, which I know they work, or try IK22, thinking that they might work better ?

Is there any other thing that could be causing this ?

BTW, my profile is ready now, too bad us newbies can't use avatars.

 

[Defiant]

You were told what you should use. That line won't be changing from us. If they're not working, you need to track down what's wrong with your setup.

 

[elfroggo]

You might want to try going up the line like swapping out plug wires. If it's breaking up top you can try to check your fuel delivery also.

 

[ECLIPSE4x4]

You gapped what plug to .028? The V Powers one or did you get some BPR's?

You have to realize man, we have all at one point had this same problem and most of the time is is because we either tried some NEW fancy plug or had the wrong gap.

We are telling you to get BPR plugs, so why ask us again if you should get the iridium?

I ran the iridium when they first came out. Biggest waste of money I ever spent on the car.

 

[Leo Rojas]

I gapped the V-Powers to .028. I was thinking of getting iridiums because they worked for me before.

I'm getting NGK BPR7ES and gapping them to .028 tomorrow.

 

[Leo Rojas]

Here's the update ...

I got the BPR7ES's and gapped them to 0.028''. At Low Boost the car was fine but at High Boost the car got better, but still has some problems.

At 4th gear, when you hit full throttle at low rpms, when it starts to boost the car begins to stutter and I can even gear the bov. Same thing happens if I do that at 3rd or 4th gear going uphill. But if I hit full throttle at 2nd gear it goes hard all the way through 5th.

What can be causing this ? Fuel ?

 

[yokotabrat]

Your profile mentioned bigger injectors, however I didn't see how you are tuning for them? You have an SAFC on your wishlist, does that mean you don't currently have one? How are you tuning for your bigger injectors? Also, how big are the injectors?

 

[Leo Rojas]

When I bought the car I didn't know how big the injectors were. When I did the engine rebuild I tested the injectors and after some cleaning they measured 480 cc/min.

I don't have a SAFC at this moment, I'm thinking of getting one.

The thing is that the car run fine at 15 psi before I began trying new spark plugs.