Spark plugs go bad if car sits for long periods of time.

[BanginGears]

Both my 440s are bone stock and sit the majority of the time. I do occasionally start them up.
So I went to go to a car cruise and both cars spark plugs need replacing. One set gas fouled, the other set looks like they are running clean but a little rusty.
Nothing bad. Replaced both sets of plugs and cars are running perfectly again. Not many miles on the plugs.
What's up with this?

 

[beanhead]

Letting an automobile sit is the worst thing you can do to it. All kinds of weird things will happen..
Starting them doesn't help much; you need to regularly get out and get some good heat in the engine, and romp on it some to clean those deposits. It also helps cook out the gunk that collects in the oil, as well as the condensation that forms in the exhaust.

If you just can't drive the car enough for whatever reason, check out what some of the cold-climate folks do when they put their rides up for the winter--
https://www.forbbodiesonly.com/moparforum/threads/winterizing-your-mopar.58995/

 

[pnora]

Starting them and short running is the problem especially if you have a choke.

 

[Ron H]

It’s kind of unusual to have the plugs go bad as a root cause anyway; but as posted letting cars sit without running them up to operating temp periodically isn’t good. Better to drive them; but my car will sit over winter for two months sometimes w/o starting it up. Even though you mention the motors run fine after replacing the plugs, I’d still check a few of the common things such as engine timing and carb adjustment. A rich mix can foul plugs, a lean setting can increase engine temp. More remote, excessive fuel pressure can also causing plug fouling. One thing I do is run good E-free gas as much as I can and especially before I put it in storage. Running an engine cleaner through the motor isn’t a bad idea for rides that don’t get much use. Another thing I’m sure you know, is oil changing, I do this without fail every year despite never putting more than 1500 miles on my ride in a season; but new oil and filter goes in. One year it was only 295 miles; but old oil out and new in. You could explore other types of plugs as another option…

 

[dadsbee]

When I started restoring my Bee in 2015 it had sat for 14 years... started up on the second crank. Those plugs had been in the engine since 1988.

 

[AR67GTX]

Starting them and short running is the problem especially if you have a choke.

Yes, this above.

 

[PurpleBeeper]

Plugs can't "go bad" sitting except maybe getting a little corrosion on the electrodes on the two cylinders that have the intake valve open....but that's a stretch

 

[toolmanmike]

Both my 440s are bone stock and sit the majority of the time. I do occasionally start them up.
So I went to go to a car cruise and both cars spark plugs need replacing. One set gas fouled, the other set looks like they are running clean but a little rusty.
Nothing bad. Replaced both sets of plugs and cars are running perfectly again. Not many miles on the plugs.
What's up with this?

Gas fouled? Not a spark plug issue.

Rusty? Where?

 

[BanginGears]

Plugs can't "go bad" sitting except maybe getting a little corrosion on the electrodes on the two cylinders that have the intake valve open....but that's a stretch

Plugs on 1 car looked clean. With mo gas fouling.
Car started hard and ran rough. Car sat for many months between starts.
Rust was forming on the outside of the plugs.
Put a new set in and Car runs perfectly. Why would a plug go bad sitting?

 

[Kern Dog]

You didn't get the plugs from Harbor Freight, did you???

 

[Don Frelier]

Perhaps it wasn't the plugs but the connection between the wire and the plug tip. By changing them you slid the wire off and back on making a "clean" connection.

 

[BSB67]

Why would a plug go bad sitting?

They don't. You've confused the cause and symptom.

 

[Wietse]

If your car is in long storage it is better to just crank the engine with a dry carb and the fuel line blanked off to the fuel pump.
At least all parts move a bit and you are throwing some oil around to keep things wet.
A cold start without bringing it to normal operating temperature just introduces fuel and moisture in the engine sump which doesn't get the chance to evaporate out again.
Also your exhaust will be standing full of water and will rust out.