kevinkpk

recommend replacing the plug wires also

Mr. Dude with a face

Do you think that is my problem?

Mr. Dude with a face

Also, how could too small of a gap be caused? Improper instalation? And also, how could too small of a gap cause my proablem?

kevinkpk

Do what you want.

Mr. Dude with a face

I just don't know, I don't have that knowledge yet, that is why I am asking.

Gumby22

You can’t trust that gauge. The beveled gauges can rarely be held square enough to accurately read the gap and the plating can have enough thickness variation to affect the reading. Wire type gap gauges and feeler gauges are much more accurate at checking gap.

If you’re unsure of how long it’s been since it had an ignition tune up, it’s recommended to change the plugs, wires, distributor cap and ignition rotor at the same time. If any of these components have been replaced more recently (since last oil change) you should be ok reusing them.

As to how a smaller gap can affect engine performance - even though I don’t think that’s actually the case here - there’s a lot to explain but I’ll do my best to keep it minimal.

If you consider static shock as a reference point, the average static charge can be around 20,000 volts, but those shocks are jumping a gap in relatively unpressurized air (technically the pressure is about 14.7 psi at sea level).

It’s much more difficult to get a spark to jump a gap In pressurized air, and as I’m sure you’re aware, compression in the combustion chamber exceeds 100 PSI (or at least that’s the minimum you want to have). That’s where the ignition coil comes in, by taking 12 volts and stepping it up to 40,000 volts or more in order for the spark to jump the gap (exact specs on the coils for these engines may be lower than 40k but that’s about the average).

Spark duration is the amount of time (in milliseconds) that it takes spark to jump the gap. Obviously a larger gap will require longer spark duration and a smaller gap will require shorter duration; and with those changes, compression will impact how long it takes.

So if the idea is to time the spark correctly to ignite the air fuel mixture at exactly the right time and maximize the efficiency of a burn, plug gap can have a significant impact on how an engine runs. Smaller gap = shorter duration (less effort) which can allow the spark to jump the gap too early. That means the mixture is igniting too early.

Now, does that mean detonation or pre-ignition are going to be problems with a gap that’s slightly too small? Highly unlikely. Again, the timing is down to milliseconds - it takes gross differences in plug gap between cylinders before you would notice anything. If the gap is significantly too small (and to be honest I’m not sure what that number is) it could effectively become a short to ground and the cylinder would be noticeably dead anyway.

I can’t tell you exactly what an acceptable variance in plug gap is without looking into it further, but chances are good your gauge will read the same gap on the other plugs as well (if they’re in the same condition as the one you posted). Even assuming the gauge is accurate, if all the plugs are the same gap, then all the cylinders are igniting at the same moment so there still wouldn’t be any noticeable effects.

Chris94

There should be a diagram on your radiator fan shroud that has both a serpentine belt routing diagram and the spark plug gap. I would say the smaller gap was probably improper installation. Even "pre-gapped" spark plugs aren't always correct, and the gap should be double-checked prior to installation. Usually the gap widens as the positive and negative electrodes wear. Your plugs don't look that bad. There is some black build up that looks kinda wet near the positive (inner) electrode on the inside of the spark plug case, but I don't see oil fouling. I would suggest replacing the PCV valve as well though. It's my understanding this valve lets blow by from the crankcase enter the intake manifold, and if it failed open, a small quantity of oil is allowed into the intake manifold which can cause fouled plugs, misfires, sludge build up, and a few other issues. I'd recommend the tune up just because you don't know when it was last done, even though it may not solve your problem. If money is tight, you can inspect each component individually and reuse what's good. I'd make an excel sheet listing the vehicle, component, date and mileage of replacement or inspection and any notes so you have a history for future reference.

ChrisFix also has a really good video detailing what to look for when inspecting spark plugs, and the different types of spark plugs.

kevinkpk

Gap is set when plugs are installed. I'd recommend when you replace them, make sure you have the right plug.

Mr. Dude with a face

Woops! Sorry, I forgot to come back and read y'alls posts! Very helpful. I know we are now heading into winter, but I recently changed my air filter, and that may have solved the proablem. If I remember, I will post an update once the weather starts getting hot again. Thanks.