2000 4runner 3.4 4wd running rough

[blueridgemt]

2000 4runner 4wd, 3.4, automatic, 238k miles.
Recent: New oil, filter, plugs (double ground), wires, coil packs (all 3), injectors checked and cleaned, pvc valve, air cleaner, and timing belt.
Has been running rough all the above has been done to try and remedy and as maintenance.
Sometimes it will run fine, other times it runs really bad (poor acceleration, missing at idle). It doesn't seem to make a difference if it is warm or cold, but it is becoming more frequent that it runs bad.
Codes have come back
cylinder 1 misfire, cylinder 3 misfire, and cylinder 6 misfire at different times over a few weeks.
When it is running rough, the CEL will come on and will flash when accelerating.
Any help would be greatly appreciated.

 

[jonwilly2]

The CEL will flash when there is a bad missfire.

where i would check in order.
-MAF sensor, If you have cleaned it and it still doesn't run right (come back later)
-vacuum leaks
-spark plugs, depending on the plugs you got your engine might not like them like my buddys 3.4 loves the bosh platinum 2 my 3.4 absolutely hates them. Is the gap correct some times you have to tune them in a bit
-sensor connections, is everything plugged in. Are there any loose connections, broken clips.
-Fuel, check the filter they are like $25 and take 10 minutes to do. Is the fuel pressure at the right psi. If you get a surging shaking feeling that scares the shiz out of you then check the fuel pressure regulator. First check for a vacuum leek then might just have to replace it.

Still no go back to MAF. One time for me I got some water in my intake filter box and it soaked the filter and when I would peg the gas it made a fine mist that hit the MAF and made it think there is a mad amount of air going in and bam like hitting the NOS button on a ricer. But then again I had been use to the damn theing running like crap for so long.

So get a MAF

The only other thing after that I could think of is the o2
-o2 sensor, ya got 2 of them a upstream and a downstream the downstream one is after the cat really isnt any good ways to check besides replacing them.

 

[Richard808]

Do you have access to a scan tool that can read live data? Id look at some of the readings while it is running poorly. If not since it is multiple cylinders from both banks it is most likely something that effects all cylinders and not just one. For instance a clogged fuel filter, 02 sensor, MAF, or something. Might not be a bad idea to put a fuel filter on it if you didnt already.

 

[blueridgemt]

Have checked for vacuum leaks and connections. Replaced the fuel filter last week. Have cleaned the MAF.
Running bosch platinum plugs, just changed within last 2 weeks, changed these out from plugs installed by Toyota about a year ago.
Have been having similar issues for about 18 months, took to dealership 1st time around & had them change the timing belt. After we brought it home, we found a bad coil and changed them & it has been running ok since.
Then it started acting up again recently.
Will check fuel pressure psi and check the connections on the sensors then if that doesn't work, I guess start changing sensors.
I have been using the scan tool at the local parts store, so no live data readings. I'll let you know what works.
Thanks for the suggestions.
Ugh.

 

[PitbullRescuer]

Along the same lines, check to make sure all your grounds are good. Never had an issue on the 4Runner but my wife's Pathfinder had two grounds that rusted through and caused a bunch of issues.

 

[Atreyus]

I actually had this issue misfire cylinder 6 p0306 code, turned out it was a bad injector hopefully yours is an easy fix, good luck.

 

[blueridgemt]

I checked connections and for vacuum leaks again (not to say I couldn't have missed something). Changed spark plugs to NKG and gap at .040 (had just put Bosch platinum in past couple months). Put new MAF sensor today and still running rough.
If I disconnect the battery it seems to run ok until I stop and let it sit and then when restarting, it runs poorly again.

 

[4runnerTiger]

2 things:

You didn't mention the IAC. The IAC is generally a cleaning and might be stuck open causing a problem?

I had problems with mine that ended up being a coolant temperature switch that sounds like yours BUT mine seemed to run much better when cold then warmed up.

 

[blueridgemt]

Took by the shop today to have code checked again and they found a bad injector that they previously said was checked and fine. Can they go bad over time working intermittently?
Seems to drive great now. Time will tell. That still doesn't explain the different codes coming back as 3 different cylinder misfires.
I just hope it's fixed. If not, I'll post more.