Sparkplugs For Vg30Dett 300Zx

[Girorostar]

Hello guys,

I'm trying to help a friend of mine who has a 300ZX with a VG30DETT engine. I know this is a skyline forum but maybe someone can help.

He's been having an issue where he keeps faulting the sparkplugs. So we asked on a 300ZX forum and they said that the best sparkplugs are

ngk PFR6B-11B for this engine. Now.. He already fault 12 of these sparkplugs and dozens of other types of sparkplugs. First we thought its because the car was running too rich, they adjusted the fuel and now the car is running good with no fuel issues but he still keeps blowing those sparkplugs.

Anyone has any ideas which sparkplugs he could use. He's running 9psi atm on stock turbo's, was planning to run 14-15psi but i think thats out of the question. Maybe some copper sparkplugs so he doesnt have to buy those platinum ones that keeps putting a dent in his pocket.

Thanks in advance, cheers.

[blind_elk]

According the the ngk website, the recommend plug is a PFR5B-11B, but if he's running a bit extra boost, then a 6 would be ok.

So, you're saying that a set of 6 brand new plugs all fail within a short space of time. Not 1 particular cylinder, but 6 cylinders fail?

If everyone else doesn't have a problem, then there is surely something wrong with your friend's car. Sounds like it must be detonating and destroying the plug tips. I would suggest contacting NGK, show them the plugs and ask what is possibly happening.

[mad082]

when you say "blowing spark plugs" what do you mean? is the car simply misfiring? if so then i'd say that it isn't a spark plug issue but an ignition issue, such as coils or ignitor (most likely coils). even if the plugs are getting burnt out, etc, then i'd still put it down to being an ignition issue rather than an issue with the plugs.

[Girorostar]

With blowing i mean burning the plugs and makes the car run on less cylinder, sorry for my poor english.

when we put new plugs in we checked if any of the coils could be the problem but all of them seem to be working fine. We took out 1 coil at a time and the cars starts working bad then we put it back in and it starts idling good again. If the coil is bad shouldnt the car be working bad all the time? How can we test if its the ignitor?

[Girorostar]

here are a few pics of brand new spark plugs that he put in on Wednesday and got burned on friday. He said he only gave it a bit of gas and they went. and car started missfiring.

these are cylinder 4 and 6.

[jhjones]

Doesn't that mean it's running rich? The pictures are out of focus.

[Girorostar]

Doesn't that mean it's running rich? The pictures are out of focus.

sorry about the quality, took them with my phone.

I'll have to ask him what the AFR is, the car was running way rich about 10 something but that was suppose to be fixed. the car is gonna get fine tuned again tomorow, hope that fixes it.

[mad082]

does he have an aftermarket ecu? if not then there isn't much that can be done about it running rich. but that problem is being caused by it running rich, so you need to find out why it is running rich. there is probably an issue with something such as the AFM or injecotrs that is making it run rich. is it only happening on cylinders 4 and 6, or all of them? if only 4 and 6 then it is that there is an issue with the coils on 4 and 6, or the injectors.

[Girorostar]

does he have an aftermarket ecu? if not then there isn't much that can be done about it running rich. but that problem is being caused by it running rich, so you need to find out why it is running rich. there is probably an issue with something such as the AFM or injecotrs that is making it run rich. is it only happening on cylinders 4 and 6, or all of them? if only 4 and 6 then it is that there is an issue with the coils on 4 and 6, or the injectors.

Yea, its got an aftermarket ECU, megasquirt i think. The car doesnt have AFM anymore, When you tune a V6, do you have to use 2 widebands? i think they're using 1 wideband which might lead to 3 cylinders on one side is running richer than the other side? That could be the problem if its running rich. Gonna ask him about that.

[mad082]

as long as the wideband is in the rear muffler then you only need one. if using it in the exhaust where it is only monitoring 3 cylinders then you would want to check the other bank after the tune just to be sure there isn't an issue with that bank. but the ecu only uses 1 lot of settings for the whole lot so what 1 side does, the other side should be doing too. not that many ecus will allow for cylinder specific tuning.

[Girorostar]

as long as the wideband is in the rear muffler then you only need one. if using it in the exhaust where it is only monitoring 3 cylinders then you would want to check the other bank after the tune just to be sure there isn't an issue with that bank. but the ecu only uses 1 lot of settings for the whole lot so what 1 side does, the other side should be doing too. not that many ecus will allow for cylinder specific tuning.

Thanks for the help man, really appreciate it.

We did some fine tuning yesterday and figure that its the injectors that are not good. Gonna get them out for testing and cleaning. Hope that fixes everything.