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Old 10-28-2009, 12:08 PM   #1
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p0304 code ugh!!!

my 4runner has been throwing the p0304 code for about a week now. i did plugs about a 3 months ago and the one in cylinder 4 which is misfiring is good, but has some white residue on it, i believe this is due to a possible malfunctioning injector. i did plug wires and swapped the coil in charge of the #4 cylinder , but the code remained with the #4 cylinder.

Im tired of dealing with it. so its going to the mechanic. hopefully its not a burnt valve.

wish me luck
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Old 10-28-2009, 04:37 PM   #2
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good luck with that man that code ment a new injector for me (p306)
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Old 03-09-2010, 03:14 PM   #3
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Got the same code, with fresh plugs, wires and the coils checked out. Injectors go bad - get them rebuilt or swap in some used ones, junkyard-style. I'd suggest swapping two injectors at a time, though, to figure out if the problem migrates with the assumedly bad injector.

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Old 03-09-2010, 03:17 PM   #4
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Good luck - if you're going to do injectors just go ahead and do them all and do it right (OEM).

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Old 03-09-2010, 04:33 PM   #5
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Fink's right. If you wind up having to buy 'em, use OEM stuff.

I should have been clearer - if you want to test for a failed injector, swap the one on the hole that is misfiring with one from a hole that's not, and see if the misfire changes holes too.

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Old 03-09-2010, 05:35 PM   #6
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Fink's right. If you wind up having to buy 'em, use OEM stuff.

I should have been clearer - if you want to test for a failed injector, swap the one on the hole that is misfiring with one from a hole that's not, and see if the misfire changes holes too.

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Old 03-09-2010, 06:22 PM   #7
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Back from the dead!!!!

It was a bad injector, which also caused a valve to get hot and stretch> i had to get the valves re shimmed and a new injector $$$$$$$ now its all good
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Old 03-10-2010, 11:20 AM   #8
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Stretched valve? That's new. Sounds like taillight fluid.

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Old 03-24-2010, 05:31 PM   #9
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been reading several threads on this misfire topic, all seem good and repeat the fundementals. However, I have a few new questions...

I have had a p0300 and p0306 since december-09, did the plugs, wires, and swaped coils, then even new Optima (it was eight yrs old!!!!!!!!) but still codes returned after all stages. it did seem to run smoother and for 300+ miles before retuning after the new Optima. Even Sea Foamed it. So have been prepping to replace injectors. I would like to test compression first but sounds as though its mute point and should likely just do them all anyway @210k this is first major running issue (I think I fouled the injector after having the throttle body cleaned?)

My concern now is the length of time I have driven with the misfire (> 2000 miles). The valves have been mentioned as the possible culprit, but I have been and now the mention by j-money about the "strecthed" valves I am wondering what damage I may be doing continuing to drive with the misfire???

What are any steps with injectors to be cautious of, like with replacing gaskets or handeling the feul line/rail?
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Old 03-24-2010, 06:09 PM   #10
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Originally Posted by zmbombr View Post
been reading several threads on this misfire topic, all seem good and repeat the fundementals. However, I have a few new questions...

I have had a p0300 and p0306 since december-09, did the plugs, wires, and swaped coils, then even new Optima (it was eight yrs old!!!!!!!!) but still codes returned after all stages. it did seem to run smoother and for 300+ miles before retuning after the new Optima. Even Sea Foamed it. So have been prepping to replace injectors. I would like to test compression first but sounds as though its mute point and should likely just do them all anyway @210k this is first major running issue (I think I fouled the injector after having the throttle body cleaned?)

My concern now is the length of time I have driven with the misfire (> 2000 miles). The valves have been mentioned as the possible culprit, but I have been and now the mention by j-money about the "strecthed" valves I am wondering what damage I may be doing continuing to drive with the misfire???

What are any steps with injectors to be cautious of, like with replacing gaskets or handeling the feul line/rail?
The catalytic converter will go bad if it gets too much raw fuel (from the miss) dumped into it for too long, that's probably your worst worry. Even then, I doubt you'll have problems, but just get it fixed quick.

I don't know about you, but I personally wouldn't spend $1200 on OEM injectors to replace ALL of them. I would rather spend $200 and start by just replacing the #6 injector since that's probably the only one that's causing your problems anyways.

From personal experience, just because one injector fails, it is not an indication that all of them are on the verge of failing - usually it's just the one. And if you do replace just the one on hole 6 and it doesn't take care of the problem, the worst case scenario is you'd have to pull off the intake plenum again in the future to change out the other 2 on that side. Well worth taking the chance to save $1000 IMO.
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Old 03-25-2010, 06:03 AM   #11
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Quote:
Originally Posted by zmbombr View Post
been reading several threads on this misfire topic, all seem good and repeat the fundementals. However, I have a few new questions...

I have had a p0300 and p0306 since december-09, did the plugs, wires, and swaped coils, then even new Optima (it was eight yrs old!!!!!!!!) but still codes returned after all stages. it did seem to run smoother and for 300+ miles before retuning after the new Optima. Even Sea Foamed it. So have been prepping to replace injectors. I would like to test compression first but sounds as though its mute point and should likely just do them all anyway @210k this is first major running issue (I think I fouled the injector after having the throttle body cleaned?)

My concern now is the length of time I have driven with the misfire (> 2000 miles). The valves have been mentioned as the possible culprit, but I have been and now the mention by j-money about the "strecthed" valves I am wondering what damage I may be doing continuing to drive with the misfire???

What are any steps with injectors to be cautious of, like with replacing gaskets or handeling the feul line/rail?
In terms of your last paragraph, I would definitely go to the auto parts store and pick up some 1/4" o-rings. When I pulled the fuel rail and re-assembled with the good injector, the other two leaked. Went and picked up o-rings and replaced all the o-rings on all the injectors on the side I was dealing with and it's been perfect ever since. Seems once those o-rings come out of the fuel rail and/or cylinder head, they are nearly impossible to get back in undamaged. The "stretched valve" thing is new to me... never even heard of that, but I have had no problems since replacing my injector, but I also didn't drive quite as long as you have on yours.
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Old 03-25-2010, 08:01 AM   #12
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Stretched valve? That's new. Sounds like taillight fluid.

STICK
yeah and i spun a muffler bearing too 8=D
The valve got hot due to a failed injector and it caused it to warp. It just needed to be re-spaced. So Yeah in a way it was stretched out.
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Old 03-25-2010, 08:31 AM   #13
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In terms of your last paragraph, I would definitely go to the auto parts store and pick up some 1/4" o-rings. When I pulled the fuel rail and re-assembled with the good injector, the other two leaked. Went and picked up o-rings and replaced all the o-rings on all the injectors on the side I was dealing with and it's been perfect ever since. Seems once those o-rings come out of the fuel rail and/or cylinder head, they are nearly impossible to get back in undamaged. The "stretched valve" thing is new to me... never even heard of that, but I have had no problems since replacing my injector, but I also didn't drive quite as long as you have on yours.
Yes, definitely do the upper and lower O-rings for all 3 injectors on that fuel rail even if you only change the #6 injector like I was suggesting. The O-rings are cheap and it will probably leak if you don't change them. Put a little Vaseline on the O-rings to before you put the injectors and the fuel rail back in or you could damage them during install.

trd_4runnin11,
Just out of curiosity, what was your indication that the other injectors were leaking when you didn't replace the O-rings the first time? Could you see gas in the valley of the block or just smell it? Or was it flooding?
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Old 03-29-2010, 09:32 PM   #14
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Okay then, how in the Hell do I test for a stretched valve? Compression? My injector went sour out in the desert, and I had to hammer the truck for hours to get out, then drive it home.

STICK

PS> Oh, and by the way, a well-applied can of Liquid Wrench makes removing hoses, O-rings and every other seal on the injector swap a breeze. Soak, soak, soak.
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Old 04-09-2010, 05:16 PM   #15
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Concerning the sequence of diagnostics, I havent been able to get the compression test done. if the injector is not bad and the valve ends up needing fixn, is it really that much double duty to worry about putting off changing the injector until I get a compression test?

(in my head I am saying "just do it all ready"!)
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Old 04-09-2010, 08:26 PM   #16
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i took it too a mechanic after i figured out it was not ignition coil/ spark related. He did a compression test, and the miss firing cylinder was at about 25% compression of the rest. After the valve was re-shimmed it was still missing, therefore requiring the injector to be bad as well.

The injector went, which in turn caused the valve to heat up and warp = lots of MONEY to fix

Good luck
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Old 04-13-2010, 04:35 PM   #17
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F me, I hope mine didn't do that. I was planning to do a wet-dry compression test, see what came of it. Fingers crossed...

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Old 04-29-2010, 05:54 PM   #18
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guys I'm getting the p0304 and for some reason in the FSM it's calling for cyl #3. Is this a misprint? I've changed the plugs twice. twice because for some reason Toyota will not take bosch plugs. New wires, swaped coils and just replaced the #4 injector. Came back after two days. thinking also the valve "stretched" haha. Anyways just a little help confirming the code. Thanks!
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Old 04-29-2010, 09:58 PM   #19
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P0304 is definitely cyl. #4 miss. Mine doesn't like Bosch plugs either, my engine turned em brown and they wore out in <a year.
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Old 04-30-2010, 08:07 AM   #20
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guys I'm getting the p0304 and for some reason in the FSM it's calling for cyl #3. Is this a misprint? I've changed the plugs twice. twice because for some reason Toyota will not take bosch plugs. New wires, swaped coils and just replaced the #4 injector. Came back after two days. thinking also the valve "stretched" haha. Anyways just a little help confirming the code. Thanks!
maybe i used the wrong terminology. The valve get hot and "cups" or warps and the stem part of the valve in turn gets longer. You may have a bad injector
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Old 04-30-2010, 08:07 AM
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