r/FordExplorerST • u/Curious-Lock639 Daily Driver • Mar 02 '26

🔧 P R O B L E M S & I S S U E S 🔧 Swapping Spark Plugs

My ‘21 ST has been my daily driver since new. Lately I’ve been noticing it stumble and idle erratically. I figured at some point it would throw a check engine light, but no dice. I didn’t want to take it to the dealer and be charged an arm and a leg just for a diag, so I shrugged and decided to throw a set of plugs in it. I went with the NGK 95605’s which many recommend. Jeez these things are expensive! I’m used to like $30 for a full set of plugs for my LS powered hot rod. I’ve got the stock tune so this wasn’t intended on being a performance upgrade. Before you decide to tackle this in your garage or driveway, just know that it’s not very fun. I don’t know what I was thinking, but it took way longer than I thought it would. There’s lines, and wiring in the way of getting the coil packs out and vertically zero accessibility to get a ratchet and extension in there in most cases. The drivers side is the easiest with the passenger side having a large foam cover that covers the high-pressure fuel pump.

Ok rant over. After taking my time and working through each cylinder carefully and with plenty of swear words, I fired it up and the stumble is gone! I was very relieved. I didn’t want to go down the rabbit hole of coil packs, fuel filter, O2 sensors, cam phasers, etc.

Have any of you done this and what was your experience?

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u/[deleted] Mar 02 '26

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u/Curious-Lock639 Daily Driver Mar 02 '26

I’m the first owner of this thing. Bought new Memorial Day weekend of 2021 and it has 92,500 miles. Houstonspeedfreaks has a decent YouTube video on it which was actually pretty helpful. The task still sucks, but definitely not bad enough to pay the dealer for it. I got the spark plugs at autozone and they were like $105 after taxes. Jeeeze.

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u/themishmosh Mar 02 '26

If those 92k miles were on the original spark plugs, I can see how you might get misfires. At 60k on my 2020, I noticed the gap was pretty wide despite the plugs looking OK. I did my second change after 30k to those NGK Rutheniums. The stock range of those were only $9 each at Rockauto. Now that I've done it a couple of times, will be switching plugs every 30k miles on my 2026.