Fouling #6 plug

[Roc87]

Hey Guys, been a while since I posted in tech, but having an issue. I rarely drive the GN and in the past 4 or 5 years have put maybe 1000 miles on it. I do keep stabil in the fuel, but had to rebuild a carb in my ATV recently that was also stored with stabil in the tank, so I'm not a huge believer in the stuff.

The GN keeps fouling the #6 plug, I can't tell if its oil or gas, I think its gas. I have swapped plugs with new, NGK UR5's gapped at 31, swapped ignition modules, coil packs, tried #6 plug wire on #2 and the #2 wire on #6, even done a compression test. Vacuum doesn't fluctuate at idle, so I am hoping its not a flattened cam (also use that ZDDP every oil change); so, before I go through the hassle of swapping injector #6 with #2 to see if now #2 fouls the plug, is there any other things to do before? Injectors don't have very many miles on them, they are the 60/65#'s that came out a few years back. Fuel pressure doesn't seem to drop very fast either.

Thanks

 

[earlbrown]

Swapping injectors is really the next troubleshooting step. checking the cam lobe is easy enough if you have a dial indicator and a mag base.

 

[turbo nasty]

My guess is the inj is dribbling bad or poor spray

 

[Nick Micale]

My approach is different, as the first thing would be a compression check, or you can start by checking engine vacuum?

Another simple test is pull the plug wire to that cylinder and see what the RPM does?

 

[earlbrown]

he said vacuum doesn't fluctuate at idle.

 

[CGASTON]

Hey Guys, been a while since I posted in tech, but having an issue. I rarely drive the GN and in the past 4 or 5 years have put maybe 1000 miles on it. I do keep stabil in the fuel, but had to rebuild a carb in my ATV recently that was also stored with stabil in the tank, so I'm not a huge believer in the stuff.

The GN keeps fouling the #6 plug, I can't tell if its oil or gas, I think its gas. I have swapped plugs with new, NGK UR5's gapped at 31, swapped ignition modules, coil packs, tried #6 plug wire on #2 and the #2 wire on #6, even done a compression test. Vacuum doesn't fluctuate at idle, so I am hoping its not a flattened cam (also use that ZDDP every oil change); so, before I go through the hassle of swapping injector #6 with #2 to see if now #2 fouls the plug, is there any other things to do before? Injectors don't have very many miles on them, they are the 60/65#'s that came out a few years back. Fuel pressure doesn't seem to drop very fast either.

Thanks

I agree with Nick. Do a compression test. There are to types, Dynamic and Static...
Static compression can tell you about the health of your piston rings, cylinder walls, and valves.
Dynamic compression reveals problems in the intake and exhaust systems of the engine.

When doing a static compression test, make sure that the engine is at operating temp, all plugs are removed, and throttle body completely open. This will all for the engine to rotate completely without any restriction.. Disconnect injectors. Allowing for a better reading. Do each cylinder 3 times and take the average of each. Out of all 6 cylinders, from the highest and lowest reading, you do not want more than 20%. If so then you have a weak cylinder.

On a Static, this is done while the engine is running. Take out plug, install compression tester, disconnect that cylinders injector from harness and get your reading. Principal is the same, but your readings are going to be less (more like 90psi).

Remember that #6 and # 1 use the same coil on waste spark. So if the coil in bad then #1 should be fowling also.

Also get rid of the NGKs and get yourself a set of Autolite AR133-134...

Clint


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[Roc87]

The compression was done with the engine fairly cold, don't have the numbers in front of me, but lowest was 107# and highest was 121# IIRC (probably a little low, but it does have 157k miles). Sorry, should have stated that the plug fouling is only noticeable when the boost passes 20 psi. I usually run 28# with the dual nozzle meth. Still seems to idle great and has around 14" of vacuum at idle

 

[Roc87]

Well, swapped #6 injector with #2, still doing the same thing. Runs fine up to around 20psi then coughs and sputters, still idles fine, and the #6 plug looks fouled

 

[earlbrown]

I would imagine a flakey injector harness would cause it to be dry instead of fuel fouled.

did you ever decide if it was fuel or oil that's fouling the plug?

 

[turbo nasty]

Post Pic of plug

 

[Roc87]

I really can't tell whether its fuel or oil, the black on the porcelain seems like its gas?

 

[turbo nasty]

Im going to say fuel

 

[CGASTON]

Are you running GAS or E85? Do you have your TT chip set to give a lot of fuel? Not enough timing?

Did you do the dynamic compression test? What does #1 plug look like? You stated that you already tried another coil.... But did you try a coil from a good know source? Maybe a buddies car!

 

[Roc87]

Running gas, 91 oct, highest available here. TT chip is base settings, haven't messed with it, BLMs at idle are 117. I need to figure out which laptop I have can run the data logger... Haven't done a dynamic compression test yet, #1 plug looks great (actually all the rest of the plugs look great). Coil & Ign.module is an OEM that was originally on car early last year. Had an issue with spark blowing out and replaced it, turned out to be weak plugs caused by spaying a mix of meth and distilled water through the engine with out boost (Stupid thing to do I know, Had the car stored and didn't want 100% meth sitting in the pump). Buddy of mine at a shop in Vegas says the injector driver may have an issue?

 

[CGASTON]

Injector driver- The plugs/injectors all would be the same. Why aren't you running an Autolite AR133-134 plug. Highly recommended, a must, for a turbocharged car. Helps to eliminate the detonation.

Is your chip burnt for race gas or pump gas?


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[Roc87]

Had had pretty good luck with the NGK UR5's in the past, maybe they aren't as good as they used to be? I have to go buy some plugs for another toy, so I'll buy a set of Autolites AR133-134 as well. Chip is Pump gas with alky, same chip that I ran my best time with

 

[CGASTON]

AR 133 and AR134. 134 are hotter plugs


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[CGASTON]

Had had pretty good luck with the NGK UR5's in the past, maybe they aren't as good as they used to be? I have to go buy some plugs for another toy, so I'll buy a set of Autolites AR133-134 as well. Chip is Pump gas with alky, same chip that I ran my best time with

What are your BLM, O2, FP at WOT


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[Roc87]

Will have to check on BLM at WOT tomorrow, don't know what narrow band o2 is showing, but wideband at WOT is 10.2:1, when running right it was around 11:1, FP may be something to look into, I don't believe it is going past 60 (have it at 38# with vacuum off)

 

[CGASTON]

Vacuum off you need to be set at 42. You are running rich on top end. Back off alky and get your AF to/around 11.5


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