99 3.6 trouble codes help

Got a 99 3.6 that just started acting up, got 0304, 0300, 0305, and 0306 and a flashing cel
Any help is greatly appreciated, this is my wifes daily, and I'm currently working thru some medical recovery, can work on it, just not for long periods.
Thank You all

 

This must be a 5VZFE 3.4 engine. These are cylinder misfire codes (P0304=cylinder 4, P0300=multiple cylinders, P0305=cylinder 5, ..). Check the spark plugs and spark plug wires. If they have not been replaced in a while, replacing them should solve the issue. Per my experience most of the time, this is it. I suggest that you use OEM parts here. If these do not solve the issue, I'd check the coils next. The only way to check a coil that I know of is to swap one with a new one or with another bank's coil and see whether the miss fire code goes away or not. If coils are OK, the issue could be fuel related e.g. dirty injectors, clogged fuel filter or even fuel pump. I suppose the ECU could also be the culprit.

 

Agreed on the plugs and wires. They are a wear item and need replacing.

The coils rarely go bad...as they are really high quality on these. If you do suspect the coil, the best is to swap two coil packs on the engine around and clear the codes and see if the misfire moves. If it moves, you know the coil pack is bad. Then get a DENSO or a TOYOTA coil pack. Don't cheap out on them.

Since cylinders 4 and 5 are misfiring, they are not tied to the same coil pack, so I would NOT suspect a coil pack. Diagram of wires on a 3.4: https://lh3.googleusercontent.com/--SMhkOoAtbc/UCwCdzMrFoI/AAAAAAAAAX8/e8flqMUT574/s720/plug_wires%28zCruiser%291.jpg

KEEP the old plugs and mark the 4 and 5 plugs and see if they are different. Plug tips can speak VOLUMES.

 

Yes 3.4, my car is the 3.6, been a long week for me.
Just did plugs, boots and wires, used good parts, always do on my wife's rig,, spring of this year, while I was doing the valve covers, had some bad leaks, also did the timming belt while I had it open, ran flawlessly all summer, pulled our boat, no problems.
Fuel pump is less than 2 years old, gets a filter once a year.
I've had an evap code come and go, but that's it

 

Since the plugs/wires are so new, it is very unlikely that they have gone bad. Looking at the wiring diagram, I see: Cyl 5+2, Cyl 3+6 and Cyl 1+4 on the same coils. Since you're getting P0304, P0305 and P0306, it is makes it hard to identify a healthy coil. The only way that I know to rule out a bad coil is to replace it with a healthy one and see if the code clears. Having said, I doubt that all three coils have gone bad at the same time. The next one is fuel. Your note states that you have replaced the fuel filter. Check the fuel pressure and see if it is within spec. If not, then fuel pump will be it. If fuel pressure is OK, you'll need to look into the injectors.

 

Can also be the fuel regulator. Not necessarily the pump.

 

Good catch

 

As you were in there recently it’s worth it to check the spark plugs to make sure they’re seated properly and aren’t fouling. Were they dual tip and gapped properly, Denso or NGK? Also take the time to check ground wire connections as IIRC you need to disconnect a ground during the process. I like to go back and check previous work when something like this pops up (relatively) shortly after a job before wildly loading up the parts cannon again

 

So, I replaced the plugs, swapped in known good coils out of another 4 runner, started looking for a pressure port for the fuel? What the best way to check fuel pressure?

 

I take it that after you swapped the coils and cleared the codes, they all came back again. Regarding fuel pressure, I have not tried the following myself but the suggestion should work.