Check your spark plugs

[lxs123]

I’ve had my 2024 Tacoma TRD Off-Road for about two years and roughly 24,000 km. Overall it had been running fine, aside from occasional harsh downshifts that I assumed were just part of the transmission tuning.

I brought it to the dealer initially because of a chirping noise from the A/C. They replaced the A/C clutch under a Toyota technical bulletin, but during the repair the radiator fan connector was left unplugged and the truck overheated.

I took it back right away for a comprehensive inspection, including a compression test. Everything checked out, so I continued driving it. After a while, though, I started noticing a fairly harsh jerk under acceleration—usually around 50 km/h, with the turbo fully spooled and the engine around 3,500 rpm. It felt like a sudden drivetrain or transmission jolt whenever I stepped into the throttle.

The dealer diagnosed it again and found that one of the spark plugs had a crack in it. They said it was likely a factory defect. They replaced all four spark plugs, and the difference was immediate: the truck now shifts smoothly and the harsh jerking under acceleration and during upshifts/downshifts is gone.

Just sharing in case anyone has similar symptoms. Before assuming it is transmission-related, it may be worth checking the spark plugs for cracks or other ignition issues.

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[Sner]

To your point, the change interval for spark plugs on the new Tacoma surprised me, every 60K km. i haven’t noticed spark plugs needing to be changed at that mileage in over 20 years. Most plugs get changed well over 100K km.

 

[lxs123]

To your point, the change interval for spark plugs on the new Tacoma surprised me, every 60K km. i haven’t noticed spark plugs needing to be changed at that mileage in over 20 years. Most plugs get changed well over 100K km.

The spark plugs themselves were not fowled just one had the ceramic cracked along its length which resulted in miss fire, further exacerbated by removal during compression test. Could be related to over torquing on the assembly line, or a bad batch of NGKs.

 

[Will721]

More likely it was due to a tech tossing them on the work bench when they pulled them out for the compression test. But as long as they replaced them it doesn't really matter I suppose.

 

[Lando]

To your point, the change interval for spark plugs on the new Tacoma surprised me, every 60K km. i haven’t noticed spark plugs needing to be changed at that mileage in over 20 years. Most plugs get changed well over 100K km.

Oh wow, I’m over halfway there then on my ‘24. Good to know, thanks.

 

[Sner]

The spark plugs themselves were not fowled just one had the ceramic cracked along its length which resulted in miss fire, further exacerbated by removal during compression test. Could be related to over torquing on the assembly line, or a bad batch of NGKs.

Wasn’t my point. Just saying the same symptoms could arise should spark plugs not get changed at proper intervals and that the new Tacoma’s change interval for spark plugs is unusually frequent for a modern vehicle.

 

[maxx075]

Wasn’t my point. Just saying the same symptoms could arise should spark plugs not get changed at proper intervals and that the new Tacoma’s change interval for spark plugs is unusually frequent for a modern vehicle.

You can thank the emissions warranty for that. Technically if you don't change them around 40k you void the warranty, but

 

[Will721]

Fun fact, manufacturers never really increased the service interval, plug companies did. A properly running engine should never foul a plug. People mistake worn out plugs as "fouled" but they actually wear out like a tire. With every arc (spark) the gap widens. Over time plug manufacturers changed the materials in the electrodes from copper, to platinum, double platium, iridium, ect. That extended the life of the plug and therefore the number of miles between replacments.

Its odd that Toyota shortened the replacement interval. I can only think of two reasons why they would do that. Either they have higher output coils for a hotter spark, which would wear the plugs faster. Or they are doing it just to cover their ass. It does make sense to require plug replacement for emissions as a misfire would degrade the catalytic converter shortening its life immensely.

 

[wongaust]

I’ve had my 2024 Tacoma TRD Off-Road for about two years and roughly 24,000 km. Overall it had been running fine, aside from occasional harsh downshifts that I assumed were just part of the transmission tuning.

I brought it to the dealer initially because of a chirping noise from the A/C. They replaced the A/C clutch under a Toyota technical bulletin, but during the repair the radiator fan connector was left unplugged and the truck overheated.

I took it back right away for a comprehensive inspection, including a compression test. Everything checked out, so I continued driving it. After a while, though, I started noticing a fairly harsh jerk under acceleration—usually around 50 km/h, with the turbo fully spooled and the engine around 3,500 rpm. It felt like a sudden drivetrain or transmission jolt whenever I stepped into the throttle.

The dealer diagnosed it again and found that one of the spark plugs had a crack in it. They said it was likely a factory defect. They replaced all four spark plugs, and the difference was immediate: the truck now shifts smoothly and the harsh jerking under acceleration and during upshifts/downshifts is gone.

Just sharing in case anyone has similar symptoms. Before assuming it is transmission-related, it may be worth checking the spark plugs for cracks or other ignition issues.

Did the jerk constantly occur even when the engine and transmission is warmed up? I have similar symptoms but only in cold starts and during warmup period

 

[Sner]

You can thank the emissions warranty for that. Technically if you don't change them around 40k you void the warranty, but

There’s more to it than emissions, drivability could become an issue due to fouled spark plugs. Turbos and higher compression ratios and heats are failure point for spark plugs

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