Hi
I changed spark plugs on my RX350 2011 at 59k miles 2 month ago and everything was fine.

Lately computer is sending random misfire codes P0305, P0302, I just plug the code reader and erase it and sometimes I just turn off the engine and then after starting it, it goes away by itself.I was thinking at beginning it could be a coil problem but misfire is random on different pistons and it if could be a coil problem, misfire should not goes away. Also it could be spark plug.Please let me know your recommendations

 

I had these misfire codes on my Sequoia... misfire could be due to a number of things, from leaking vacuum, bad spark plug wires, bad spark plugs, bad ignition coils to bad fuel injectors ... in my case, after replacing all ignition coils the problem was still there ... finally, after replacing a faulty fuel injector my misfire issue was resolved ....

You can try to swap out the ignition coil from a problem cylinder to a good coil from another cylinder that didn't get the misfire code to see if the misfire code moves to the new cylinder then your issue could be a bad coil ... if not, try to replace possible bad injector ... good luck ...

 

Did you use OEM spark plugs? RX are finicky.

Salim

 

I have misfires in Rx450h after scheduled diy spark plug change.
It was all good prior to service. I used Denso FK20HR11 plugs.

There are no DTC present but I used live monitor to see misfires appear in cylinders 2 and 4 mainly while idle, no misfire in moderate rpm (you can't force it high rpm in stationary state in maintenance mode)
Luckily misfires happen in the bank 2 which is easy access.
Have to figure out what is causing them

I have never sofar had problem after spark plug replacement in other vehicles...

 

Were the plugs gapped correctly? Loose spark plug cable?

(Does the 450h engine use spark plug cables or is it coil on plug?)

Using the Torque android app with an ELM327 plug Torque says it is monitoring misfires on my 450h using the Toyota Prius PIDs while I am driving.

 

Try swapping coil of 6 with 2. If no change then swap plugs of 6 and 2. You can add 4 in the mix, but keep a chart and try not to do too many swaps at one time. You can check the gap but they should not be re-gapped as it compromises the strength of the bent electrode.


Salim

 

Hi Salim
Denso Iridium

 

Thank you guys for all kind of recommendations.So far not more misfire after replacing all spark plugs for NGK LFR6AIX-11, even first set was NP FK20HR11.

 

Thanks for help. Updated situation, some time passed and misfires happened mainly in cylinder 2. Cylinder 2 spark plug had cracked in the porcelain insulator. I don't remember whether new plug was already cracked prior to install it but I would doubt I could miss so obvious fault. You can see black burn marks, current has stroke through the insulator.
I replaced it with visually best looking old plug that I had not yet disposed. No misfire since that.

 

buy OEM one and don't look back