Checking Spark Plug gap

[Jozef Zoldos]

I am changing plugs and got a new set of Motorcraft SP-509 as recommended. Many people say "check the gap" before you put plugs in. I have never done that before. Is this a necessary step if the plugs are brand new?

 

[99WhiteC5Coupe]

I am changing plugs and got a new set of Motorcraft SP-509 as recommended. Many people say "check the gap" before you put plugs in. I have never done that before. Is this a necessary step if the plugs are brand new?

I own a 2015 Ford Expedition Limited 4x4, and have changed the original spark plugs with new Motorcraft spark plugs (don’t remember the number).

GM (not Ford that I’m aware of) has issued a TSB stating not to adjust the gap on spark plugs that have an iridium tip coating - as the coating can be damaged.

I believe the SP-509 plugs have the iridium coating, so I would not adjust the gap.

You can buy a spark plug gap gauge at most auto parts stores - to check the gap prior to installation. GM’s TSB states to not use an iridium plug with an improper gap.

 

[762mm]

If you're careful, it can be adjusted without "damaging" anything. Just don't push the gapping tool against the center electrode with any amount of force when checking the gap.

I replaced mine with Champion iridium plugs about a month or so ago and had to adjust each one. Since they are meant for many vehicles, they came pregapped at 0.041, whereas I needed 0.054 (quite a difference).

I gapped the plugs, installed them and the truck runs great. By the way, the safest tool to check gap is this wire type, which is what I bought & used :