jeff1a

I thought I would share my recent experience with ignition coils.

I purchased my RX300 in August of 2021 with ~216,000 mi, the car now has 226,000 mi. The previous owner told me he had recently replaced one ignition coil and all spark plugs. It ran fine until probably a month ago though there were times when it would intermittently hesitate like a miss, no codes were generated. A little more than one month ago there was an instance where the engine hesitated quite a bit for a short distance then ran fine. I found the pending codes P0300, random misfire, P0304 & P0306, misfires on cylinders 4 & 6.

It continued to run fine for a few weeks then started to miss badly at times, the check engine light flashed then when the engine started running fine the CEL stayed on steady. P0300 and P0306 were stored. I swapped the #6 and #2 coils and the problem went to cylinder 2. I bought a new coil at Auto Zone, installed the new coil at 6 and returned #2 to it's former spot. The car ran fine for about a week then started to miss again along with the CEL flashing then turning solid. Retrieving the codes found P0300, P0304, P0301, P0303. Monitoring misfires with a scanner revealed that 4 misfired often, 1 &3 less often.

Given the above I decided to order a set of new NGK coils from Rock Auto along with a new set of NGK spark plugs. I did this because it was nearly the same money to buy a set of 6 as to buy 4 separately and this was I have 6 identical coils.

I have run the car for a week now and has run fine. I noticed coils removed from 1,5, and 6 were not original the rest appeared to be . The coil removed from 6 a week prior appeared to be original. The removed spark plugs looked fine and were Denso iridium plugs.

Conclusions-
1) I believe cold weather seems to have been some influence on making the engine run worse.
2) I still drove the car waiting for the new coils, found that if I drove the first 1/3-1/2 of my 21 mile commute with over drive shut off the engine did not miss nearly as bad.
3) The use of a scanner was helpful as I could monitor misfires while driving the car.
4) I should have just replaced all the coils right away, the previous owner had an issue, I knew I had a previous P0304 code, and the original coils were over 20 years old. Could have saved myself $80 for the coil I bought at Auto Zone.
5) Access to the front 3 coils is easy, the rear 3 not so much.

I hope this might help someone with similar issues.

farmer33

It might be your Bank 2 oil control valve. Cheap easy fix.

sktn77a

iTrader: (2)

Multiple cylinder misfire codes are not unusual when the problem is only in one cylinder. Fix that and they all go away. No idea why! I've had my RX 23 years and have seen this a couple of times.

jeff1a

Thanks for the replies.
At this point I believe it is fixed. I have put over 800 miles on since replacing all the coils and the engine has run flawlessly since, even in sub zero weather.

I suppose I may have put more parts in than needed. Engine ran good for a couple hundred miles after replacing #6 coil then started misfiring again just on different cylinders. The worst misfire was on #4, maybe replacing that coil only would have taken care of the issue. Given there was a possibility of 3 faulty coils felt it was better to spend $230 (probably closer to $250 with shipping and tax) for 6 new NGK coils than spend another $80 for one and possibly needing two more.

I kept the known good coils, hopefully I won't need them!

jeff1a

Update-

A few weeks ago engine started running poorly at times, retrieved codes P305 for misfire on #5, monitored and found that #5 was indeed misfiring. Swap #5 and #6 coils and problem moved to #6. Swapped #6 coil with a known good coil and problem went away. Drove car another week and #4 started misfiring, swap known good coil and engine ran fine. At this point I warrantied the whole set of NGK coils I installed in January. I drove the car for another week without incident while the replacement coils were being shipped. Installed the new coils and car runs fine.

Little disappointed that the coils failed in 4 months, I put around 6000 miles on during that time. I believed buying NGK coils would assure me of OEM quality, now not so sure. Hopefully this set will last longer.

Can't complain about Rock Auto customer service. It did cost me between 7 and 8 dollar for shipping but was issued a refund for the warranty coils I sent back in a timely manner.

Any one know of something that would cause coil failure? Spark plugs were replaced at the time the first set of new coils were installed. Car running fine after installing the warranty set of coils.

Margate330

Yikes, not what I wanted to hear.
+1 for sharing that and heads up.
Just bought qty 6 NGK coild from Rock Auto before christmas because they were out of Denso.
Figured can;t go wrong with NGK but now I hear your story and has me nervous.

lizzyb222

Has anyone considered trying what farmer33 said regarding the Bank 2 oil control valve? I'm having the exact same problems and I'm hoping you guys figure them out before I get ready to work on mine!

salimshah

What exact codes are you getting?

Bank 2 [or even 1] on all cylinders of that bank, can come from the bank OCV. If it is only one or two cylinder code, then swap coils and plugs from a good cylinder.

Salim

jeff1a

In my situation I did not believe there was and issue with either control valve because the code each time was for one cylinder and when I swapped a coil from a suspect cylinder to a known good cylinder the problem followed the coil. Need to know what code(s) is/are being generated in order to diagnose. If you have multiple cylinders on same bank misfiring then it could be the oil control valve. If it's only one or two cylinders on a bank or cylinders on different banks it's probably an issue with coil(s). Cylinders 1,3,5 are in back 2,4,6 are front.

lizzyb222

Wow! This appears to be a great place for questions and answers. Starting with such a quick response to my comment. Thank you in advance! I by chance, stumbled in here after I googled P1354 & random misfire on '02 Lexus RX300.
Here are the codes I first pulled up:
P0300 random misfire det. Severity 2 of 3
then P0301 0302 0303 0304 0305 0306
P1354 VVT System (Bank 2)

I'm a newbie with Lexus. Just bought an '02 RX300, at auction....yikes! I hope I didn't bid myself into some trouble.
I have more questions and info, I'll get back here in a little bit. As I will most definitely be looking for additional input.🏜️

jeff1a

Given you have P0301,0302,0303,0304,0305,0306 indicating every cylinder is misfiring I doubt it's a coil issue. P1354 suggests an issue with the oil control valve for bank 2. That would not affect bank 1. If they are not too expensive you could change both control valves. I have not had to change the valves but a previous post says it's not difficult.

Margate330

If you guys like to save money $$$ and have average DIY skills can I plz recommend the Hantek automotive scope for approx $120.00.

I have one of these and with this you can scope the crank sensor at the ECM and so much more for hard codes like this.
BTW, plz tell me about your tachometer- is it jumping all around at idle with engine warm when it is misfiring?

Hantek scope
* for scoping cranshaft sensor, fuel injectors, ignition coils, VVT sensors, etc, etc

maxSteel

When there are multiple codes reported the usual troubleshooting order is:

1. DTCs other than fuel trim malfunction (DTCs P0171, P0172, P0174, P0175) and misfire (DTCs P0300 – P0306).
2. Fuel trim malfunction (DTCs P0171, P0172, P0174,P0175).
3. Misfire (DTCs P0300 – P0306).

So address the P1354 first.
You should also try clearing all the codes and seeing which one is reported first

Margate330

I'm glad someone caught that.
Plz let me 2nd this.

Codes other than misfires should be checked out first like posted above.

jeff1a

Another update-

Mid October 2022 shortly after a morning startup I noticed the engine running rough, drove it a couple of miles and the miss did not clear up so I drove home found misfire on # 6, replaced that coil with known good one, engine ran fine and proceeded to work. Within a week had same symptoms, had misfires on #2 & 3, replaced those coils with known good ones and engine has run fine since, a little over 3 months.

Being the coils are still under warranty I obtained another set of NGK coils from Rock Auto, installed them and sent the coils that were installed in May back for warranty reimbursement. I am very disappointed with the performance of the NGK coils, Rock Auto has been good about honoring the warranty, (3 years or 36,000 mi).
It is interesting that NGK coils are not offered by Rock Auto as an option for my car at this time. Makes me think there is an issue with them.