trivium

I wanted to know when it would be time to replace my spark plugs. I have 41k miles and I have a suspicion that when I start my car it is not 100%, maybe 95% and sometimes it sounds different. I also have minute idling issues from time to time (like when I shift from 1st to reverse the idle fluctuates annoyingly and from R back to 1st it does also but not when moving from 1st- 6th consecutively).

RACER

A tan colored plug means that the engine is running normal and the air/fuel mixture is correct. This is the correct color a spark plug should be and it tells you everything is fine with the engine. You would install a new properly gapped plug. When installing a new plug, replace the old one with the same heat range. This plug shows normal wear in the center electrode. A new plug would have square edges that helps the plug fire better.




This plug is worn out from being used for a long period of time. Notice how the center electrode is round and worn from use. A spark plug that is worn takes a lot more voltage to fire and can cause poor engine running.




This plug shows what can happen when something hits the spark plug. Something from inside the engine has hit the plug and this problem must be repaired before running the engine further. Make sure the spark plug is the correct length for the engine.




Excessive detonation has caused the porcelin on this plug to break away. If this engine is allowed to run, engine damage can occur. Make sure the fuel octane is high enough for the engines requirements.




A white colored plug is caused by engine overheating. Failure to repair this engine will result in severe engine damage. Common causes for this are:
Incorrect spark plug (too hot heat range).

Low octane fuel.

Timing is not set properly.

Cooling problems, (dirty cylinder fins, no or low water if water cooled, low or no engine oil).

Carburetor air/fuel mixture is too lean (too much air).

Leaking crankshaft seals, no oil, base or head gasket leaks, or crankcase leaks on two stroke engines.




This plug has ash deposits which are light brownish deposits that are encrusted to the ground and/or center electrode. This situation is caused by the type of oil used and adding a fuel additive. This condition will cause a misfire. This can be also caused by changing oils in midstream.




This plug is oiled fouled, caused by poor oil control.




Pre-ignition, which will usually look as a melted center electrode and/or ground electrode. Check for incorrect heat range plug, over advanced timing, lean fuel mixtures or even hot spots or deposit accumulation inside the combustion chamber.




Sustained Pre-ignition, which will usually look as a melted or missing center electrode and/or ground electrode as well as a destroyed insulator. Check for incorrect heat range plug, over advanced timing, lean fuel mixtures or even hot spots or deposit accumulation inside the combustion chamber.




Splashed deposits look as if they are small islands of contaminants on the insulator. This is usually caused by dirty carburetor bores or air intake.




A black dry fluffy colored plug is caused by deposits from a carburetor that is running too rich (too much gas), or excessive idling on some engines. Black smoke coming from the exhaust is a sign of a rich air/fuel mixture. The rich air/fuel mixture must be repaired before installing a new spark plug. Common causes for a rich air/fuel mixture are:
dirty air filter.

air mixture screw or carburetor needs adjusting.

choke is sticking.

carburetor float height is out of adjustment or float is sticking open.

trivium

Carburetor?!?! An s2000 uses a Carb?

RACER

I gave you examples of all the possible scenario's of what a spark plug could look like.

RACER

too rich


Too lean


Oil fouled


Prolonged use


Things such as too low of an octane, over advanced timing, too lean or too rich could potentally cause spark plugs to look like some of the ones in the pics.

If your plugs look like the plug in the first pic, then your engine is fine. If your plugs look like one of the plugs in some of the other pic's, there would be a problem with the engine.

RACER

Or the wrong type of fuel.

CoralDoc

Note that our cers come with platinum-tipped plugs and they will not look like the ones depicted above. The center electrode is a LOT thinner.

Also, these plugs are supposed to last 100k miles, but if there is a fueling issue, this number can be dramatically diminished. I chose to replace the plugs on my first S2000 at 50k miles and I did not notice much of a difference. YMMV. They are not cheap - about $40-50 for a set from discount sources.

Ray K.

I thought platnums were good for 30k miles give or take? Maybe that is the case in my other car since it's a turbo charged vehicle.

brimstone

Wow, even the extreme condition maintainence schedule lists the spark plug change at 105,000mi, certainly wasn't expecting that. I was thinking of changing mine out at the same time as my injectors, or if they're in good shape, have their gap adjusted. Damn, what an awesome car =D

RACER

Both platinum and irridium are much stronger than conventional spark plugs. This allows the center electrode to be considerably smaller in diameter, thus producing a more concentrated, efficient spark.

I suppose after a while, the edge of the electrodes can become round, thus reducing efficency. I only have 20k on my car, so I dun't know how long it will take for the electrodes to wear out. Keep in mind, the electrodes can become corroded with deposits. I do suppose that if one is carefull, these plugs can be cleaned and re-installed.