First off I'm want to say that I have been search Google for answers to the cause of this code and I'm coming up with a bunch of different problems/solutions.

I bought this car (2001 GS300, 170k miles) about 6 months ago but have only put about 3k miles on it. Car was running just fine when I got it until fairly recent. It started with a rough idle at a stop light that would then clear up once you would drive it and no check engine light. Then a week or so later it's got the check engine, VSC, VSC Off lights on the dash all the time. I borrowed a buddies code reader and it comes up with P300, P302, P304, P306. Looking up those codes it's a miscellaneous misfire and the misfire on cylinder 2, 4, and 6.

When I bought the car 6 months ago they had done a bunch of stuff to the car like changing the timing belt, valve cover gaskets, as well as new spark plugs and wires.

When I search on the internet I've see all sorts of things come up as the cause like OCV, spark plugs, coil packs, and fuel injectors. It also looks like the spark plug remove is fairly time consuming. What is everyone doing to troubleshoot this issue. Since the spark plugs and wires were recently done do I just start replacing the coil packs and maybe the OCV? Is there a way to troubleshoot the coil packs vs wires vs spark plugs?

I'm going to get it over to my dad's garage in the next few days since he has more tools than I do and I guess start pulling the intake off to get to the spark plugs. I hate to pull it apart and not really have a plan as to what to do other than start throwing new parts on the car.

Anyone have any suggestions as to how you would start troubleshooting the issue. BTW, the car feels like it's misfiring so I'm sure it has something to with spark.

 

The simplest thing to do first of all is to clean the OCV. Clear the codes and then take it for a drive. Without knowing if the plugs they used were the right ones, if the coil connectors were replaced etc. it will be hard to troubleshoot any further.

Give that a try and report back.

 

Its not your spark plugs . Cylinders 2 4 and 6 is bank 2. You could have a bad o2 sensor. Check b2 fuel trim if its lean then i woild go with the o2 sensor.

 

No it is not. Please look at how the exhaust manifold is made on the GS before spouting mis-information.

 

I'll give you a hint!

 

Thanks, I saw where some said it could be the OCV but that usually gave the code of P1349. I also saw where it could also be the OCV without showing the P1349 code. I hope that's the case because the OCV looks to be a whole lot easier than dealing with the intake for the spark plugs or coil packs. It will probably be next weekend before I can get the car into the garage to look at it. I'm still helping out on a Camaro that needs to be finished up to make room first. Luckily this car isn't a daily driver just yet so it can wait till the weekend.

As for the O2 sensor, I'm not saying that isn't the problem but I would have thought it would throw a different error for that. Plus the car feels like it's misfiring like a bad spark plug or wire or something. I didn't think the O2 would do that.

I'll let you know how it goes. Thanks for the suggestions.

 

Decided to go look at the paperwork from when I bought the car and there is a laundry list of stuff that was replaced but this is the spark plugs and wire information which I assume are correct.
NGK 7092
NGK Iginition wire set (WPC F1020573465NGK)

No mention of coil packs though. Which I have a quick question on that, from what I saw on a video about changing the spark plugs it looked as though there were only 3 coil packs. How many coil packs do these have?

 

Those are not the correct plugs for your car and you only have 3 coil packs. The car runs on a wasted spark system.

 

Just found where the NGK BKR6EIX-11 is what is others have used. Is that the recommended plug?

I'm assuming you think the NGK 7092 they have listed could be a cause for my issue? I looked it up on Amazon and it says those plugs should fit an '01 GS300.

 

They will physically fit but will not perform as they should. Look up the double plat replacements.

There may be quite a few possibilities causing the codes.....primarily I would look at the Coil connectors, Plugs and then coils in that order. With the mileage and unknown condition of those items, it will be very difficult to help you diagnose any further.

 

@Letsride....thanks for all the help. This is exactly the kind of stuff I'm looking for.

I found these on eBay and they say they fit. Is this what I should get? They sure are a heck of a lot cheaper than what I've found on local auto parts stores. I'm a little concerned they are cheap for a reason though.
https://www.ebay.com/itm/4pcs-New-Se...-/291852776595

I hate to just throw parts at a car but it sounds like I need to upgrade the plugs and if I'm already there why not change the coil connectors for this price (assuming they would work).

 

Those connectors will be fine. Most of the time all that needs to be replaced is the black outer shell.....but do inspect the wires for being brittle.

 

If the problem is with every other cylinder, I wonder what the odds are of an ignitor or ecm issue? No argument that those are not the correct plugs, but as far as the coil packs, they fire one even and one odd cylinder, so if a coil pack or connector was bad, wouldn't codes throw for the odd- numbered cylinders too?

 

These are the NGK plugs I've found based what others have used. Are these what you would suggest as well?

 

These are what I use!