Like so many other 3.4 owners I ended up getting these codes intermittently on my 4Runner a couple months ago which was about a month after I decided to retire my old 86 1st gen from daily driving to something more reliable. I have an Ultra Gauge so I am able to look at the CEL codes wheb they happen and I would get a pending P0305 than the P0305 would occur (Flashing CEL) than about a minute later I would get the combined P0300, P0302 & P0305 codes.

By researching this and other forums as well as using the FSM I started to diagnose the problem. Here is what I did which pretty much was in step with the trouble shooting procedure:

1st thing - new NGK Plugs and wires which are Standard Ignition #5605. The old plugs looked in normal condition except the #5 was darker than the rest. -- Result no change

2nd thing - cleaned MAF sensor with CRC MAF cleaner. It was filthy and definitely needed it but there was no change to the error code occurrence.

3rd Thing replaced - PCV Valve with a Standard Ignition part # V388. Result no change to CEL

4th thing - replaced coil pack on the #5 cylinder. I assumed that since both the 2 and 5 spark plugs are fired by this coil pack it must be the problem. Again I used the Standard ignition part # UF-156. There was no change in performance.

5th thing - I decided to replace fuel injector #5. My reasoning on just one was that I assumed that because P0305 started the chain of reactions and P0302 came slightly afterwards the P0302 was caused by changes in the ECMs control of the coil pack to compensate for P0305 and not an issue with that cylinder. I used Standard Ignition Fuel injector #fj585 and ordered 2 seal kits SK53. (Note the seal kits are not correct, they fit a 22RE fuel injector not a 3.4L). I installed the fuel injector today and the CEL is gone with no codes. The old injector had no resistance and was definitely bad. I test drove it up and down some PA mountain passes today and the engine runs better than it has since the day I bought it.

I am not going to say how much I paid for the parts because it is not fair to everyone since I get them at a huge discount as a dealer for them. However I can update everyone if issues do arise with these parts. I know they are not Toyota OEM parts but because I sell standard ignition parts at my store I feel compelled to test how well they work.

Hi,

I'm glad to read it all at all worked out and it's running better now.

I disagree with you about not stating what price you got them at. I mean you can always just say you have a private hook up and got them 40% off. We're all strangers so what does it matter.

Who cares how much he paid lol. He shared how he fixed the issue, which is the real bonus for this thread. Thanks for sharing!

Brian,

The reason I do not disclose the price I pay for parts is because as the manager of my store I have experienced issues from some of my employees stating what they pay to purchase items and then someone else coming in and asking for the same price. It may not happen on this forum but has happened before. If I state I am able to get a $120 part for $50 because I am employed by a company that offers deep discounts on parts, inevitably it will come back and cause issues by someone down the road.

Thanks. That is very interesting about the misfire on the paired cylinder to one with an injector problem. That's new data to me and very useful to keep in mind.

OK. I guess it isn't so much your post but there are so many posts especially dealing with purchases where it is rare to see the prices.

I have no idea how much a decent deal on injectors are, yet alone a great special price. It's great you can get those prices though!

You got it fixed. Congrats. Hopefully someone can benefit from your experience.

I have had good luck with Standard Products, although they have all been used on American cars and trucks. If it works for ya, drive on.

Assuming #4 is a typo. Cylinder 5 & 1 are not fired by the same coil. 6&3, 5&2, 4&1 are fired by the same coil.

Thank you for your helpful post. Right now, I'm just beginning this very same journey & missing/misfiring problem. I have a 2002 4Runner, SR5, 2WD V6 w/about 260,000 mi. When I took the vehicle into a local shop (not Toy Dealer) they ran a scan w/the code P300, and diagnosed a bad coil pack which they replaced along with 2 plugs & a wire/boot.

When I picked-up my vehicle, it seemed to run great, with no misses/misfires. Drove it a few miles and back home. Next day, I ran an errand that was about 10 miles away, and after about 5 miles the vehicle started missing again. This time, the misses/misfires are not as bad as before, and more intermittent. Why run great one Day 1, and then back to misfires on Day 2?? Weird, and not sure where to proceed next.

You are correct it is 5&2, I will edit the initial post. #5 and #1 have coils on top of them so it would be very hard for them to share a coil

Yeah, I got these two codes today while I was driving my kids to school. On my way back home, I went to the local autozone and that is where the store rep. came out and got my OBD read to me. First was the 0300 and then the 0301. She mentioned I should probably change the plug(s) and if that didn't fix the problem, then the wires should need replacement as well.
I got my 'runner January 2011 (in virginia) with 177,633 miles on the odo and it has now 199,752 (in Montana). That's 22,119 miles I've put on it. I have not ever changed out the plugs or wires. It could be that they need to be. I do not know if the previous owner ever changed them out either.

Doesn't take very long to pull a couple of spark plugs and look at them, especially if you don't have any maintenance history from the PO. I bought my 4runner a few years ago with 150,000 miles on it and even had the maintenance history on it but to my unpleasant surprise, I found that the OPO had installed Champion spark pugs and cheap plug wires. I did not have a CEL but after changing everything to NGK/Denso , the 4runner ran much better. It is always better to check these things out regardless of mileage or history after buying a used vehicle.

Thanks for the info, will see if it works for me as well.