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Rb20 Constantly Fouling #6 Spark Plug ?

Cr@zY FreD

By Cr@zY FreD,
in Engines & Forced Induction

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Cr@zY FreD Collaborator

Cr@zY FreD

Posted
Posted

Hi

I have just brought an R32 gts-t with RB20det

After a while it developed a misfire, i pulled the plugs and noticed #6 was totally black while the others where white/grey like they should be

So i did the following things

- Test coil packs and swap them around

- Replace coil pack loom

- Compression test 158-163 across all cylinder s

- replace spark plugs

....but it continued to foul #6 after a while, people would look at the fouled plug and tell me its fouled by fuel

so then i

- had injector cleaned and flow tested (thinking injector #6 was dribbling, it tested fine)

- leak down test on #6 cylinder which got 85%

....but it still fouls continually #6, runs better with nice clean injectors but still fouls #6 and develops a misfire ?

when i come back from a drive remove #6 plug to check it i look down the spark plug hole and the piston looks very wet

Anyone have any ideas ???

Maybe an ECU fault ?

Sinista32 Grand Master

Sinista32

Posted
Posted

Who and when was your last tune done ?

That's where i'd be looking based on the actions you have undertaken so far. (AFR's)

Edit: compression looked okay. Leakdown on remaining cylinders ? other than 6 ?

SIFTY32 Proficient

SIFTY32

Posted
Posted

your compression results are excellent for an rb20det I've checked a dozen or so and most are not above the 140psi range...

the first thing I'd do is check the ecu for fault codes and go from there, quite possibly a faulty igniter module or ecu...

Cr@zY FreD Collaborator

Cr@zY FreD

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your compression results are excellent for an rb20det I've checked a dozen or so and most are not above the 140psi range...

the first thing I'd do is check the ecu for fault codes and go from there, quite possibly a faulty igniter module or ecu...

Tried another igniter module and it was still misfiring, although plug was fouled by then

15% leakdown is not good. How does it compare with the others? Try a hotter plug in that cylinder.

Didnt test amy other cylinder with leakdown test, came with BCPR6ES gonna get some 5's tomorrow but all that will do is prolong the fouling

Suggesting missfiring in 6 not burning fuel. Smarts

Dont think there is a misfire before the plug has fouled, the car idles sweet and revs clean all the way to 7000rpm untill #6 fouls

Thanks for ideas everyone

Cr@zY FreD Collaborator

Cr@zY FreD

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Just put the hotter plug in #6. There's no reaon why it will "prolong the fouling". It will either cure it or it won't.

The BCPR6ES's i had in there foul pretty quickly, tried a BCPR7ES that i had hanging around and that fouled just driving down the street.As hotter plugs are not as prone to fouling i thought id try some 5 heat range plugs which would not foul as quickly but im sure will eventualy foul. Pretty sure it is not the heat range of the plugs which is causing the fouling

what condition is the coil pack harness in? changing the plug isn't going to solve the problem , put a multimetre on the plug for the coil pack with the car running and test the voltage getting to the coil pack

The coil pack harness was replaced with a good cond s/h one, have tested the continuity of the ignitor but yeah ill test voltages running to the coils

Had another thought, the engine may have blown a headgasket then been chemiwelded, the chemiweld has sealed the water passages up so no oil or exhaust charge is getting into them but oil is getting into cylinder #6 which is causing the fouling.

But i thought the leakdown test would have shown this???

KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted

The BCPR6ES's i had in there foul pretty quickly, tried a BCPR7ES that i had hanging around and that fouled just driving down the street.As hotter plugs are not as prone to fouling i thought id try some 5 heat range plugs which would not foul as quickly but im sure will eventualy foul. Pretty sure it is not the heat range of the plugs which is causing the fouling

The coil pack harness was replaced with a good cond s/h one, have tested the continuity of the ignitor but yeah ill test voltages running to the coils

Had another thought, the engine may have blown a headgasket then been chemiwelded, the chemiweld has sealed the water passages up so no oil or exhaust charge is getting into them but oil is getting into cylinder #6 which is causing the fouling.

But i thought the leakdown test would have shown this???

Your leakdown test was what I understand to be in the unacceptable range (15% leak) so yes there is an underlying problem. Who did the leakdown test and did they offer any analysis? My engine runs fine without fouling plugs - my compressions are way below yours but a leakdown test resulted in 5% to 8% range - not flash but I have no discernable problems.

I am not suggesting that incorrect heat range for the plugs is your problem - I'm just suggesting you try a hotter plug (or full set if you're so inclined) to see if it will fix your symptoms short of pulling the engine and stripping it down.

Cr@zY FreD Collaborator

Cr@zY FreD

Posted
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Your leakdown test was what I understand to be in the unacceptable range (15% leak) so yes there is an underlying problem. Who did the leakdown test and did they offer any analysis? My engine runs fine without fouling plugs - my compressions are way below yours but a leakdown test resulted in 5% to 8% range - not flash but I have no discernable problems.

I did the leakdown test and my analysis in i think my engine i trucked

I am not suggesting that incorrect heat range for the plugs is your problem - I'm just suggesting you try a hotter plug (or full set if you're so inclined) to see if it will fix your symptoms short of pulling the engine and stripping it down.

Yeah replaced all spark plugs with 5 heat range as overtightened thermostat housing and broke it so cant drive car till i get a new one :-(

Thanks for your help

Cr@zY FreD Collaborator

Cr@zY FreD

Posted
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Posted

I'd get the injectors flow tested. The injector might be a bit leaky and pouring excess fuel in

yeah had that done

marked #6 injector and it was tested first and tested fine, two others ended up being leaky so two s/h replacements and cleaning and flowing cost me $260 to not fix the problem :-(

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