4.0 multiple misfire 5 and 6 cylinders

So I have a 2009 Toyota Tacoma extended cab 4.0 4x2 had it since new first 4 years was used on weekends only then daily drove ever since i do the oil changes around 3-5k miles spark plugs every 150k miles the alternator front wheel bearings at 300k cylinder 5 coil pack denso at around 480k the thermostat with waterpump at about 40k miles ago has 557k miles now and recently been getting a multiple misfire that turns to a cylinder 5 and 6 misfire along with bank 1 and 2 lean codes compression test for most cylinders are about 149psi 151psi except cylinder 6 is 146psi and 5 is 147psi the fuel pressure is at 41psi at idle it doesn’t drop when you rev it so assumed it had to be the maf replaced with a dealer part worked good for 2 days then started again switched the coil packs the codes stayed on the same cylinders replaced the spark plugs (cylinder 1,2,3 have slight oil on the porcelain from valve cover tube seal leak 4,5,6 are dry) and it ran good for a week then started again usually happens after going through rain puddles or the next morning after sitting through heavy traffic on my way home the symptoms are usually rough idle then under more of a 1/4 throttle it starts shaking usually about 35 mph check engine light flashes get the code reset it then it may fail again and I reset it then it works perfectly fine the rest of the day 120 miles of highway and city driving goes up to 80-90 like nothing next day sometimes it’s normal sometimes it does it again also when it’s raining my tail lights seem to stay on and abs lights tend to go on and flash as well my headlights dim with the flashing and the rough running engine every battery it’s had since brand new has leaked acid and the headlights have always burned out about every year for 50k miles so maybe an electrical issue not sure what to look at or test wouldn’t want to rebuild the engine and have the same problem the transmission oil has never been changed it’s as dark as dark can be I did a slight drain and fill of 1 quart of oil and it fixed a slight slip I really love this truck would like to get it to a million miles

 

Following thread just for informational purposes if you get it figured out. Hopefully it's something simple like a bad fuel injector or something along those lines, good luck. Also just out of curiousity, do you use iridium plugs for your 150k miles spark plug intervals on your truck or copper plugs?

 

If I have time this weekend I will be checking grounds and ignition and injector wire harness for any shorts or breaks in the wires before I start digging into the engine

Yeah I used the denso iridium I probably should have replaced them before but they still had the .44 gap at 50k miles and the truck would run fine so I kinda just not messed with it until I noticed it was 150k so the rest i used the same ones

 

So it’s been 3 weeks since I fixed the truck and it’s been running great. I noticed when replacing the valve cover gaskets the coil boots were fragile and tore easily when cleaning the oil out of them from leaking valve covers I ordered Standard Motor Products part# 8220-05337723 it’s a coil boot, spring, and gasket rebuilt all the old coil packs I thing looses it’s resistant for that many miles so the new one definitely helps. When I took the upper intake off to remove drivers side valve cover I noticed there was oil residue going to the cylinders especially 5 and 6 the ones with misfires so I when ahead and cleaned it and replaced the pcv valve with genuine Toyota it was about $7 when you order online at their website to pick up at your local dealer put it back together and viola no more misfires

 

Are we talking miles, or kilometers here?
If miles, you did a good job taking care of that engine.
That’s a lot of miles.

 

So a bad pcv was the culprit?
Imma have to remember this

 

He said miles!

Good job taking it this far op!

 

550k miles with no trans fluid change? Do you believe that all this talk of oils breaking down over time and creating problems is just a conspiracy of some sort? Why do you change the engine oil? Seems contradictory. I don’t see how that transmission will make it to 1M miles on the original oil, but i wish you luck on your efforts to test that theory. I am quite shocked that the only problem after 550k is the slipping.

 

Very normal, I had a truck apart with around 100,000miles/160,000kms that looked worse.

 

Ok, I gotta share too. This was somewhere in the 490s I think (mileage). I just wiped inside each port as clean as I could, this image is before I did that. was an oily residue in each.