surf4runner

sorry for another one of these...

2002 4runner 3.4L 280,000mi

persistent P304 codes

so far i've:
searched
new MAF
new plugs, wires.
swapped coil packs
new PCV
serviced the injectors
new plenum gaskets
good compression

started after a shop used several cans of carb cleaner to replace the cam seals.
result: oil crystallized on the heads and likely everywhere else. i removed 2+ handfuls of "sludge" from under the valve covers.

numerous oil treatments and it still idles rough.
occasionally will backfire when cold during hard acceleration (on ramp)

still get P304 and P300, a few P301 (same after swapped coil packs again)
i reset the CEL and it will stay off... until i restart it.

runs much better than before.

any ideas what i should check next?

vacuum leaks?
sticky valve? running a qt of marvel mystery oil this change
timing belt is due for replacement...

wyoming9

iTrader: (1)

What do your plugs look like?/

Do you keep checking them as this is a misfire code and if you have enough crap in the engine perhaps they are fouled out.

You did put the correct plugs in??

***The shop that screwed your engine up is paying for all this I would hope??

I have to wonder the oil was getting back into the pan let alone what the oil pick up screen looks like.

Now you said the compression is what it should be ?? So that I hope rules out any valve damage from lack of oil.

If you had a sticky or burnt valve the compression would be low on that cylinder Pull the plug on # 3 cylinder.

I am thinking this has to be a compression or valve related issue only because of all the crap in the valve covers.

surf4runner

same type NGK plugs ive always run have never been fouled or discolored, which surprised me even with weak injectors.
actually they look good

compression was close to #2 and #6, didn't check the other side.
ill do another round of all 6 and see how the plugs look since the injector service.

i am scared of what the pick up tube looks like. :O
i shop vac'd a significant amount out, it was that bad.
i got a low oil pressure light, which is what led me to the leaky valve covers...
unbelievably, oil did make it back into the pan

chunks did come out during the next 2 oil changes.
flushed with seafoam.

when i serviced the injectors (last thing i did), i looked again and now its looks like a maintained 280K mi engine.
seemed to stop an oil leak (rear main seal?) too.
i also switched back to reg oil from synthetic during all this.

a sticky valve(open EX) is what ive been thinking (thats what the MMO is for) since it seems to not run rough at speed and the mileage went up 2 mpg.

the INTAKE side looks OK viewed down the plenum. no build up on the stems.