05RX330AWD

I intend to switch over the Ignition Coils from # 2 & # 4 cylinder to verify if indeed the issue is with the coil for cylinder # 4, although I did erase the code once before & it took about a week to reappear.
Is this normal?
The only issue is that fuel consumption is a little high, other than that, the vehicle runs great.
The previous owner did replace all the spark plugs & 1 ignition coil 10,000 miles ago.
Which ignition coil is unknown & I have no idea whether the outfit that did the maintenance is reputable or not.

Lexuswiz

iTrader: (1)

Is it running harsh? Misfires will cause an increase in fuel consumption but if its not misfiring consistently, I wouldn't say the increase in fuel consumption will be noticeable.

Also depends, the interval in which the code reappears will depend on how many time the ECU logs a misfire. I've seen misfire codes reappear immediately and some over time due to a bad spark plug vs. a bad coil.

Definitely do the swap to isolate if it's a coil or plug problem.

05RX330AWD

Misfire codes for any vehicle are definitely new to me, the RX starts right up, runs fine at idle, amazing acceleration, nothing seems abnormal at all.
The fuel consumption is from day one since I first purchased the RX, is it possible that a ignition coil can deteriorate slowly? or is it cut & dry, as good or no good.
As soon a it warms up a bit in the next few days the swap is on, interesting to see how long it will take for the code to show up again, hopefully it's a spark plug, less expensive & less hassle to purchase on this tiny Island than a Denso coil.

Lexuswiz

iTrader: (1)

A coil is pretty cut&dry, only when it consistently misfires will it be an indication to replace. Obviously in your case it looks like the inconsistent misfires is showing a deteriorating coil that's not dead just yet.

I doubt it would be the plug, the one time I got a bad plug on my Highlander, engine couldn't idle properly. It's very obvious for a bad plug unlike a coil pack which can be discrete or obvious.

05RX330AWD

Appreciate the analysis, I'm fortunate it's a even number for the front cylinders & not a odd number for the back cylinders...
I suppose I will have to order a Denso Ignition Coil once I confirm that is the issue after the swap. Thanks!

05RX330AWD

Well, after a few months the PO304 code is back...
most likely the Ignition Coil is towards it's final end, time to check that out with the swap while the code is present.

05RX330AWD

Unfortunately a hacker previously worked on Cylinder 4, the first thing I noticed the retainer for the electrical connector was broken off.
I tried to pull out the Ignition Coil, it needed a lot of force which was unusual since Cylinder 2 came out easily in order to swap.
The issue was the rubber boot from the Ignition Coil stayed stuck on the Spark Plug.
I will have to order a new Ignition Coil (& Spark Plug, just in case) & deal with it then.
Put all back together as it was, no PO304 Code as yet.
Also the great but strange thing is my MPG jumped from 14 MPG to 19 MPG City.
Wanted to purchase a new Ignition Coil, Toyota dealership quoted $180. settled for one at the wreckers with 50,000 miles on the vehicle for $50.