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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
What does it mean when the spark plugs are a brown rusty color? The tips of the elctrodes are black and the inner tip is black in the middle and brown around. (Bosch Platinum +4's) They have been in for about 2,000 miles.
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1988 GTA 5.7L TPI Auto
355 ci. block, SLP Cold Air Intake w/ K&N, fully modified MAF Sensor, TPIS 52mm Throttle Body w/Air Foil, Fully Ported and Polished Plenum, Nikel-plated Ported SLP Siamesed Runners, Ported TPIS Big Mouth Intake Manifold, stock heads w/ 1.52 Comp Cams Self-aligning Roller Rockers, TPIS ZZ-9 Roller Camshaft, TPIS Valve Springs, Cloyes True Double Roller Timing Chain, TPIS Adjustable Fuel Pressure Regulator, Balanced Bosch 22 lb/hr Fuel Injectors, MSD 6AL, Taylor 10mm Wires, Bosch Platinum +4 Spark Plugs, MSD Blaster Coil, March Underdrive Pulleys, 6 3/4" Vibratech Streetdamper, TPIS Level 4 PROM, 160 T-stat, Low Temp. Fan Switch, Stock Distributor w/ Bronze Gear, SLP 1 3/4" Headers, Random Technologies High Flow Cat., Adjustable Borla Cat Back Exhaust, Flow Tech Pre-Cat 3" Exhaust Cut Off, Level 10 PTS-3 700R4 Trans, B&M Holeshot 2400 Stall Converter, B&M Trans Cooler, TCI Aluminum Finned Trans Pan, Torque Converter Lock Up Switch, 3" Balanced Aluminum Driveshaft, 3.73 Richmond Gears, Auburn Pro-Series Differential, Aluminum Differential Cover w/ Main Cap Preloads, BF Goodrich Drag Radials 255/50 R16, Hotchkis Lower Control Arms, Hotchkis Panhard Rod, Hotchkis Tie Rod Adjuster Sleeves, Bilstein Heavy Duty Shocks and Struts, 1LE Springs, Energy Suspension Polyeurethane Bushings, Global West Tubular Subframe Connectors, Global West Steering Box Brace, HP Motorsports 3 Point Strut Tower Brace
A light tan to brown color is normal on a normal plug. The +4 Bosch plugs probably wouldn't be any different. The blackened electrodes are also normal, since there is a lot of ion activity in these areas when the spark is generated. As long as only the conductive tip areas of the electrods are blackened, that is normal.
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Later,
Vader
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As Vader said, a light brown(tan) color is typical of a good burn.
But, what I think you are describing is completely different than a light tan/brown color. Sounds like you are describing a copper/brown rust color(like an old penny or a brown crayon).
If this is the case, then you are looking at a plug that's been fowled by Methylcyclopentadienyl
Manganese Tricarbonyl (MMT).
MMT is a fuel additive that is seldom used here in the states. It's extremely controversial, just as TEL was in the 70's.
MMT is used frequently in Octane Boost, especially in the brand "104+ Octane Boost" and "Super104+ Octane Boost".
If you are using an octane boost, and have this kind of fowling, don't worry about it. MMT fowling is quite harmless, and should be viewed the same as a tan colored plug.
Let us know what kind of fuel, or octane boost you are running.
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[This message has been edited by Steves ZZ5 (edited March 10, 2001).]
I do use a fuel additive for when I go to the track. It's made by NOS and supposed to boost octane number by 7 pts. It's the race only additive. They claim it contains Nitro-Methane. This may be the reason that it looks like this, the rust color. Thanks for the replies.
Old post I know but thought I’d add a photo of my spark plug condition. Distinctive brown spot on one side of the plug. White deposits on the side electrode.
That's a little better. The brown color is not a problem, and neither is one side of the porcelain being darker/lighter, either. It depends on the prevalent direction of flame travel in the combustion chamber that can cause different temps and what's burning where in there as the engine runs. Grab a good magnifying glass and check the porcelain and metal bits for any blistering or nodule deposition, which could indicate detonation. I'd not worry about those colors.
That's a little better. The brown color is not a problem, and neither is one side of the porcelain being darker/lighter, either. It depends on the prevalent direction of flame travel in the combustion chamber that can cause different temps and what's burning where in there as the engine runs. Grab a good magnifying glass and check the porcelain and metal bits for any blistering or nodule deposition, which could indicate detonation. I'd not worry about those colors.
