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.

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