Loose Spark Plug From The Factory

I recently tuned my truck with OVTune using their new VFTuner software. Even though I’m only at 35,000 miles I decided I would change my spark plugs to ensure the best performance with the new tune. They are expensive spark plugs, cost me just under $22 a piece plus tax at a local Toyota dealer.

I started on the left side (drivers side) bank of the engine working from front to back. The drivers side is more work than the passenger side but the whole job is a piece of cake none-the-less. I removed all the ignition coils and laid them on the engine cover in the order they came out. I moved on to the right side (passengers side) and proceeded to remove all the coils. When I removed the last coil closest to the firewall (right next to the bright silver high pressure fuel pump), I noticed it was a more brownish color than the other coils. I laid it with all the others for comparison. It was very clearly a different color from all the rest. With all the coils out, I gapped all the new plugs and proceeded to change them out one by one (I don’t like leaving a hole into the combustion chamber for very long). This is where things got interesting...

All the plugs were barely tight, it took a very minimal amount of torque to break them free, I could have broke them free with a 1/4” drive screw driver. When I got to the last plug with the brownish colored ignition coil, I found the spark plug was loose! There was evidence of blow by happening on the plug as well. Oil and fuel have been blowing past the loose threads and onto the ignition coil creating the brownish color and a brown tip on the spark plug (see attached pictures). I’ve always noticed a little spark knock on hot days, I wonder if this was the culprit the whole time. I installed all the plugs, put some dielectric grease on the inside of the coils boots and put it all back together. I cleared the learned values for the engine using VFTuner and immediately noticed a difference in how the truck ran. It runs smoother and has slightly better power all through the RPM range. This loose plug must have been causing a lean condition on that cylinder as well as a loss of compression. I’m glad I decided to change them long before they were due. I think everyone should check theirs as well because I doubt my truck is the only one.

This is the second thing on this truck that was screwed up from the factory, the first was the transmission low on ATF. Is Toyota’s QC slipping it’s what? These big oversights are not confidence inspiring at all. Check out the attached photos for reference.

Pro Tip: if you plan to do this job yourself, don’t fully remove the brackets for the intake plenum on the left bank of the engine. Only remove the top bolts and the 10mm bolt for the AFR sensor harness. Then loosen the lower bolts and just swing the bracket out of the way. It’s way easier than fully removing the lower bolts and then trying to get them lined up when re-assembling everything.

 

I didn't know VF tuner was available for the AT's. Yeah lose plugs are fairly common. Although mine weren't

 

Wow good catch, man. Makes me want to check mine now...

But maybe not In the 110 degree St Louis heat

 

I had one that was a little loose when i replaced mine

 

What mileage did you replace yours?

 

VFTuner is but the tune packs for AT have not been released yet. I’m using a pre-release non-editable tune.

 

Also check your differentials, I didn't check my front yet but on the weekend when I drained the rear and measured it was over a quart low...from the factory...can't wait to check my sparkplugs...

 

no doubt it was loose
may have loss a modicum of compression
i dont think damage was done to the engine

actually plugs 1 & 6 look bad ( as U have them line up )
running lean / over heated
not sure exactly which cylinders they came out of

tip
i use a 4 X 4 block o wood drilled for the sparkplugs & valves.........numbered
( analytical retentive/ ocd )

quite a few OVER tighten risking head damage
( 2 piece spark plugs on fords are nightmare !!! )

 

100k ish

 

This is nothing new. Some of the 3rd gens are known to have loose spark plug issues like they were Monday or Friday builds or something. Your engine is fine. I have pulled plenty of loose spark plugs off of vehicles before and replaced and things have been just peachy after. Misfire recedes and the engine just keeps on truckin'.

 

Ain’t nothing wrong with those plugs! Clean them up and slap them back in for another 35,000 miles.

 

Already changed diff fluid and transfer case fluid.

 

I won’t even touch Ford spark plugs. I bought the tool to remove broken ones just in case but luckily I’ve never had to use it.

 

Checked mine the other day and they all clicked at 13 lb-ft. And yes, with that little torque on them to begin with, it doesn't take much effort to break them loose. And yeah, top drivers side plug is a pain to get to especially with a torque wrench.

 

was going to do mine since it's been swimming twice now, but at 40,000 mi post swim, all the seals were good and the fluid was still pretty clean. After my 50,000 mi change and the last free one, I'll be looking to go heavy duty with the good stuff. Probably redline MT90 or something similar.

 

then U already know what im talking about ......................

 

I know I’ll get a lot of shit for saying this, but I’ve never torqued a spark plug in my life. I’ve never stripped one out, damaged one, or had one come loose. I really don’t think it’s necessary, maybe for someone who doesn’t have a lot of experience working on cars, but once you develop a feel for it, it seems a little overkill. Head bolts, main studs, bearing caps, etc, I totally understand but a spark plug... nah.

 

When you pass a Jeep on the trail with a blown up 4 l ask him what went wrong and he'll say something like he's never torqued a bolt in his life

roommate says the same. He's a die-hard GM guy, and he says torque wrenches are a scam.

 

I used OEM Toyota fluid for the diffs and transfer case. Holy shit was the OEM transfer case fluid expensive, and they don’t even put it in a bottle, it comes in a can!! After changing them out, shifting between Park-Reverse-Drive while stopped was A TON smoother.

 

I didn’t say a bolt, I said a spark plug. I’ve got Snap-On digital torque wrenches but trying to finaggle one into a tough spot with an extension or an adapter is not going to yield an accurate torque spec anyways.