I have 259k miles on our 2000 LC (bought it from the dealer as a lease return in 2004 at 31k miles. It threw a code for the first time ever in June '25 at 251k miles which was ignition coil/spark plug error on cyl. 5. I put a new plug OEM plug in cyl 5 and swapped the coil with cyl. 3 and the fault followed the the coil position so being pressed for time and not wanting to pay a fortune I bought a no name generic coil on Amazon for $21 and called it good. Back to running as smooth as a Swiss sewing machine like before until last week at 259k miles it began running rough after driving in light rain and shut off and re-started an hour later. No CEL but hesitated almost as if the trans was slipping. I put my head in the sand and refused to accept it could be the trans so I started by replacing all new OEM plugs. I noticed almost all of the ignition coils had signs where they had arced to the tube and the plastic shanks had split lengthwise and some splits were wide enough to see the copper windings.
After the 1st incident, I bought 2 OEM Denso's to keep in the truck along with a code reader lest it happen again on a road trip. This time I put in 2 of the new Denso's and bought 6 more of the same cheapo's on Amazon, trusting them because the one from 6 months ago runs fine. In the end, It's my fault for thinking the coils could last 250+k miles in the first place. I will be buying 6 more OEM Denso's a few at a time when I have some spare change, then swap out the faux coils with real ones.
Interesting in all of the rough running after the rain it never threw a code. Relieved it wasn't the trans. Happy Thanksgiving to all!
Edit: I'm thinking the reason it didn't throw a code was even though the coils were cracked and leaking off a charge arcing inside the tube, the computer did see they were firing and perhaps passing enough juice to the plugs to spark them as well (?) and I didn't drive it far enough afterwards for it to learn a trend (?). I forgot to mention the same plugs had been in it since the 1st timing belt change at 106k miles. The electrodes and gaps and porcelain look very good but they are a bitch to remove after leaving them in so long so I replaced them all this time with OEM plugs from Toyota which have been sitting on a shelf in the shop for a couple years.
After the 1st incident, I bought 2 OEM Denso's to keep in the truck along with a code reader lest it happen again on a road trip. This time I put in 2 of the new Denso's and bought 6 more of the same cheapo's on Amazon, trusting them because the one from 6 months ago runs fine. In the end, It's my fault for thinking the coils could last 250+k miles in the first place. I will be buying 6 more OEM Denso's a few at a time when I have some spare change, then swap out the faux coils with real ones.
Interesting in all of the rough running after the rain it never threw a code. Relieved it wasn't the trans. Happy Thanksgiving to all!
Edit: I'm thinking the reason it didn't throw a code was even though the coils were cracked and leaking off a charge arcing inside the tube, the computer did see they were firing and perhaps passing enough juice to the plugs to spark them as well (?) and I didn't drive it far enough afterwards for it to learn a trend (?). I forgot to mention the same plugs had been in it since the 1st timing belt change at 106k miles. The electrodes and gaps and porcelain look very good but they are a bitch to remove after leaving them in so long so I replaced them all this time with OEM plugs from Toyota which have been sitting on a shelf in the shop for a couple years.
Last edited: