Hey guys

I pulled these stock platinum plugs on my car and replaced them with NGK iridium (one step colder) plugs. What do you think. Was I runnig rich (that's possible b/c I was running the pre-production ecu for 3-4 weeks while my ECU was in Japan). These plugs ultimately began misfiring - roughening up the idle tremendously. THe new plugs solved that problem in a snap.

Sorry, i didn't take a close up of the electrode itself. But the surface was basically black, just as you can see in the picture.

Thanks in advance

--Gurgen

 

From that photo...it sure looks like it was running rich to me!

 

What color does a lean engine plug has? I thought black = Lean and white = rich ...

Thanks,
Az

 

exact opposite

 

I did not have my thinking hat on Thanks

 

Thanks guys. thatwas my thinking. I was worried tha ti was leaking oil (bad rings). But it is dry, burned carbon deposits (no oil). I shouldn't be wrried right?

If the carbon deposits are in fact from being rich, that does not surprise me. The stock G35 sedan runs 10.5 to 1 A/F in stock form! After the ECU, that is not a problem anymore.

Gurgen

 

From what we have seen this year alone.
Do not run colder plugs in this motor.
Two things will happen that are not good.....

- increased water temp....(with this motor that leads to other things not working)

- missfires

The colder plug puts the spark more in the block and less in the combustion camber.

The spark plugs go right into a water jacket on this engine.
The water temp has a critical point that after it goes beyond...... bad things in the engines electronics start happening.

Run the OEM 5 plug or something that cross references to it!
trust me.......we just lost two engines last week.

 

I'm assuming he went one step colder for his TT aplication. Even with TT would you still suggest staying with stock spec plugs?

 

THe shop manual specifies the "6" plug as an option! And what do you mean by the spark being more in the block? The sizes of the plugs are identical. Especially when the shop manual approves/options the use of the "6" plug, how ca it possibly lead to the delitirious effects that you speak of? I have no doubt that you know your stuff, but please explain.

Also, I am going with TTs, don't you think I NEED colder plugs.

--Gurgen

 

PLFR5A- 11 has a little more thread than the PLFR6A-11.
If you had a plug that was 3 or 4 steps colder than the
PLFR5A-11... the tip wouldnt even be in the combustion chamber.
Therefore the 5 puts the tip in the combustion chamber a little more and away from the water jacket.
The tip of the 6 plug wouldnt screw down as far so the tip will be more in the water jacket. This puts the heat of the plug more in the water jacket which causes the water temp to go way up.
The water temp with this engine is very critical to how the engine behaves.

Once again I am just passing along information that we are learning about the engine.

 

They look identical to mine when I took out my stock plugs.

 

What are your opinions on running colder plugs with Nitrous? I have not heard of any problems with one step colder pluges as of yet, But it seems that lots of people are running them in their car.

 

I'm running 2 step colder plugs right now (Denso IK22). I have a seriously rough idle and I am going to be taking them out and putting the recommended plugs back in as I wait for FI in the future. Thanks a million for the heads up BJ. I was a bit sketchy about the bumpy idle after the install.

 

We tried .....the Denso's last year at Phnx and the water went through the roof.
Our engine builder had been running these Bosch plugs in our two motors this year......we are now back ot the OEM 5 plugs.

 

didnt change the plugs in my g and it has twins

still stock plugs

 

Cant see real close but that plug look fine. They have carbon buildup which is normal. excessive buildup means rich(appears like layers of black charcoal like coating).

If they are not black but brownish white, that is a lean condition.

 

Manrey

Thanks for the reply. That is what I thought. I was just afraid that I ahve leakig rings or smth. But the deposits look like dry, black carbon deposits - which is runnig rich from what I thought.

Gurgen

 

gurgen he said what I said on G35Driver, black is a normal condition. excessively black is rich, (where it will just powder off)

If you are running rich, then you aren't running VERY rich, jsut a lttle

BTW, if you can afford twins, you should be able to afford a wideband oxygen sensor which will tell you if you are running rich.

Also, how long have you had the crawford plenum? If you didn't put it on until late in your car's miles, the Rich condition could be from the front two cylinders getting shorted of air at higher engine speeds. After the crawford you shouldn't have that problem, but if you ran 10-15 k miles then yes you will see some more carbon buildup onthose two plugs than the rest.

 

Yes these are stock plugs with about 15K miles before the crawford install. also, the 03.0 sedans run 10.5 a/f stock - so this is not surprising.

However, I did have my crawford on for 8K or so before I got these plugs. Don't think that the 12.8 A/F would just clear the plugs up. Now I have got new iridiums i there. I am plannig to take them off just to see their condition, but I doubt that they are gonna be like this.

EDIT: I wil be getting an A/f gauge.

Gurgen