Sadly, yesterday afternoon I hopped in the car to head over to my parents house for a quick visit and noticed that after the normal engine startup and warm up, the check engine light came and stayed on even after the engine had warmed up a bit. Took the prius instead and decided to wait until my local shop was open today. This is the first time ever seeing the CEL on my dash. I took it to the shop and my tech pulled code P0300, engine cylinder misfire. He quoted me about $330 worth of labor and was able to get all new spark plugs and OEM Lexus ignition coils for a little less than $100 each from a Lexus dealer in Arizona. Hopefully, this will fix the engine knocking that I've had since I bought the car. I had concluded that it was "normal" to hear the knocking for about 30 seconds on startup and would go away considering everyone on the Highlander/RX forums were saying it was normal, I'll admit that a part of me always knew and assumed it was not. 2 years later I guess I finally got my answer! I also had noticed when I first bought the car it was averaging a surprising 24.8-32mpg depending on traffic/driving for a few months until the cold start engine rattle started happening a lot more often (almost daily). Recently, I've noticed that my mpg had lowered as far down as almost hitting 19.8mpg with a lead foot, I took it easy on the throttle afterwards and was only ever able to recoup to about 22-24mpg at best... 28mpg maybe if I was going about 65mph on the freeway in the slow lane... behind a semi lol. Recently, on a trip down to San Diego I averaged about 26 mpg at 60mph for about 100, and after 2 years of averaging relatively low mileage I thought this was "good enough"...

Here's to hoping that come this week with the code cleared and all new spark plugs/ignition coils it will run properly again!

FYI for those of you saying its normal to have your engine knocking on start up even if only slightly.. it's NOT!

 

You may still have the cold start knock after replacing the plugs and coils.

It is mostly a cold start oil feed issue to the VVT and/or piston slap. Once pressure builds up and/or the car warms up it stops. Depending on who you talk to, both are cited as the noise source. It will not cause any long term harm.

See these comments from the bobistheoilguy lubrication forum

https://bobistheoilguy.com/forums/th...n-slap.213482/

https://bobistheoilguy.com/forums/th.../#post-4863833