Plug Fouling

[66yostagea]

Since fitting the forward facing plenum the plugs foul in less than 2000ks. I pull the out clean them up and put them back everything fine goes like a rocket. Then she went again today. BCPR7ES gapped0.8 are what I have been using. When they come out they are totally sooty. Black as. Have a set of the pre plenum change plugs that had done 7000ks, they look OK. Still see the white of the insulator.

How do I fix this? I have a DFA and hand controller. Will this fix it? Or is there some other sensor that is off its face.

Your thoughts would be welcome.

[DeanR33]

Since fitting the forward facing plenum the plugs foul in less than 2000ks. I pull the out clean them up and put them back everything fine goes like a rocket. Then she went again today. BCPR7ES gapped0.8 are what I have been using. When they come out they are totally sooty. Black as. Have a set of the pre plenum change plugs that had done 7000ks, they look OK. Still see the white of the insulator.

How do I fix this? I have a DFA and hand controller. Will this fix it? Or is there some other sensor that is off its face.

Your thoughts would be welcome.

I don't know much about forward facing plenums, but can't see why it should foul all your plugs.

It could be your o2 sensor, but I would expect poor running too if it were that. Also coolant temp sensor. You can meter the temp sensor to see whether it's giving the correct readings, but the o2 sensor isn't that easy, though the voltage should cycle on it.

Another possibility is plugs that are too cold, though I wouldn't say that sevens like you have would normally cause this.

Even maybe FPR

Are you doing lots of short runs? After a good motorway run, the plugs shouldn't be black.

Basically, we need more info on what level of tune/mods you have and how it's running in general to give more advice.

Edited October 8, 2010 by DeanR33

[Duncan]

strange hugh. I don't have any fouling issues, and run copper plugs with my FF plenum. It is probably not directly related

[KiwiRS4T]

Hotter plugs may help - BCPR6ES. You can't really tune it with the DFA without a wideband. If you are finished your current set of mods maybe you should splash out on a dynotune.

[pipster11]

pull the plugs and coils out, disconnect the cas and crank it over

watch the plug holes for any vapor, because the cas isn't connected the injectors shouldn't fire but if you see vapour coming out there is fuel getting in = injector seals

i'm guessing that its a s1 here = same injectors as r33's which sit in the fuel rail and fuel flows around them unlike r34/s2 injectors which have the hose on one end

you may need to get the fuel rail machined or just get new seals

[66yostagea]

pull the plugs and coils out, disconnect the cas and crank it over

watch the plug holes for any vapor, because the cas isn't connected the injectors shouldn't fire but if you see vapour coming out there is fuel getting in = injector seals

i'm guessing that its a s1 here = same injectors as r33's which sit in the fuel rail and fuel flows around them unlike r34/s2 injectors which have the hose on one end

you may need to get the fuel rail machined or just get new seals

Yes, it's an S1 Auto.

I'll give that a try. Anything actually.

If it is leaky seal(s) would that not impair performance all the time? And would some plugs be sooty and others not. In my case all the plugs are Sooty.

[66yostagea]

pull the plugs and coils out, disconnect the cas and crank it over

watch the plug holes for any vapor, because the cas isn't connected the injectors shouldn't fire but if you see vapour coming out there is fuel getting in = injector seals

i'm guessing that its a s1 here = same injectors as r33's which sit in the fuel rail and fuel flows around them unlike r34/s2 injectors which have the hose on one end

you may need to get the fuel rail machined or just get new seals

Yes, it's an S1 Auto.

I'll give that a try. Anything actually.

If it is leaky seal(s) would that impair performance all the time? And would some plugs be sooty and others not. In my case all the plugs are Sooty.

[66yostagea]

What I have done today is to run a less restrictive line to the fuel PRV. It could have been choking a bit.

Cleaned the plugs and bingo.

Started first kick and was able to balance 50c piece on the top radiator support. So its smooth.

If it plays up again I'll try the CAS check of Tom. Just trying one thing at a time. Too often I have done too much stuff and dont know what fixed the problem.

I'll keep you posted.

[pipster11]

it'll probably run ok buy be uber rich

i put a safc on my 32 and turned the mixture right up and it still ran fine (+20% fuel) and sounded smoother but sounded like it had bogged down a bit

see how it goes, if they foul again then its something to look at

could have been that when you were installing the f-facing plenum the injector seats were off or the o-rings no longer fit

[66yostagea]

it'll probably run ok buy be uber rich

i put a safc on my 32 and turned the mixture right up and it still ran fine (+20% fuel) and sounded smoother but sounded like it had bogged down a bit

see how it goes, if they foul again then its something to look at

could have been that when you were installing the f-facing plenum the injector seats were off or the o-rings no longer fit

I did not pull the injectors out and replace the o rings but I did put in the new plastic insulators. The question I have about the injectors is that if one did leak internally would it make all the cylinders run massively rich??? I would guess that if the prv was not working properly that all plugs would foul.

[pipster11]

shouldn't cause them all to foul

what do you mean by the plastic insulators?

[66yostagea]

shouldn't cause them all to foul

what do you mean by the plastic insulators?

Nissan call them "Insulator Injector" From memory it seals the injector body to the inlet port and insulates it from the heat of the plenum to prevent vapourisation I guess. Its on page EN108 of the R33 manual.

I have had R30s since new in 1984 and the only problem I ever had with them was the prv. When it spits the dummy it will start but not run over 1200revs.

I'll go for a 200k run and see how the plugs look when I get back.

[66yostagea]

I refurbished all the earthing leads and put in extras. The earth wires at the front of the plenum were not tight down as the bolt had bottomed. That seems to have fixed the sooty bit, but it still got its knickers in a knot, now and again, for no apparent reason.

Checked all the vac/boost lines and found the one to the PRV and to the inlet of the MBC and to the actuator were a bit sus. So clipped them.

Its early days yet but on a couple of 40k trips up and down the mountain it has not missed beat.

One suggestion for folks wanting to fit a forward plenum, the connections for the lines at the back of the plenum come out at rightangles.

I would suggest putting in a right angle fitting then they would be more upright an accessible.