P0304

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Twospeed
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P0304

Postby Twospeed » Wed Mar 11, 2020 4:09 pm

Well, here we go again. After the new heads were installed it's been running great until Sunday. I started feeling a miss when idling. Then it started running really rough. P0304 code thrown. So I switched the #2 and #4 coils. Same error so I thought fuel injector. I swapped out the fuel injector with a new injector but I'm getting the same P0304 code being thrown. The spark plugs are new but I'm going to swap it out next. I can't win.


Twospeed
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Postby Twospeed » Wed Mar 11, 2020 6:06 pm

Changed the spark plug with a new one. Still getting the P0304. I'm not sure where to go from here. The engine was running beautifully. Great power and 3 more MPG. It was idling smoother than it ever has. It's not using any oil. It's got close to 2000 miles since the new heads. I guess I get the FSM out again. :(

the ocho
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Postby the ocho » Thu Mar 12, 2020 7:23 am

is it possible it's in the wiring harness to the coil? does the connector look ok? Everything would have been moved to get the new heads in, and probably settled back into position by now...

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smj999smj
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Postby smj999smj » Fri Mar 13, 2020 3:26 am

do a compression test on #2 bank. use a noid light to confirm incident injector is getting power and being fired by ecm, second. last, check coil circuit.

Twospeed
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Postby Twospeed » Fri Mar 13, 2020 7:48 am

That's the plan for Saturday. I checked the wiring to make sure everything was plugged in correctly. I'm going to start with a fuel pressure test. When it first started, I thought it was running out of gas so I'll try that first. The fuel pump is about six years old. Then move on to the compression test. I was running it yesterday and decided to see what would happen if I disconnected injector 2. There was no difference in the way the engine was running. I did some research and saw where there were several incidents when people had the P0304 error and it turned out to be different things, like a fuel pump or a vacuum leak. I checked all the vacuum hoses and they all look good. No cracks or anything. I'm able to pull a vacuum without effort.
Last edited by Twospeed on Fri Mar 13, 2020 8:12 pm, edited 1 time in total.

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smj999smj
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Postby smj999smj » Fri Mar 13, 2020 7:32 pm

Sounds like a good plan!

Twospeed
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Postby Twospeed » Sun Mar 15, 2020 12:34 pm

Well the engine didn't eat itself. I'm pretty sure it's the fuel pump but I don't have a way to test it yet. The kit I purchased that said it worked on my PF, doesn't, so I'll send it back and get the correct adapter. I tested the compression on all six cylinders and they range from 178 to 182 PSI. I'll get the adapter Tuesday and test the fuel pump. I'm sure it probably is the fuel pump because I just filled the tank. Can you siphon gas through the fill tube on a Pathfinder?

weaver
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Postby weaver » Sun Mar 15, 2020 10:17 pm

Thanks to you folks for the great info. I haven't siphoned fuel on the Pathfinder, but on other vehicles I have used a cheap fluid transfer pump ($15+-) from Harbour Freight (they're also at any auto parts store, Meijer, etc.) to drain fuel tanks. The gas eats the cheap plastic ones, but I get a couple uses from them. (I "suck" at manual siphoning, faster for me to use pump) I used the drained fuel in the mowers just in case the gas had crap in it from the pump. It didn't take too much time or effort to pump 10 gallons out of my CJ-5, which has a very constricted and bent/angled fill tube, I suspect the Pathfinder wouldn't be too bad. Hope the fuel pump does the trick for you.

Twospeed
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Postby Twospeed » Sun Apr 05, 2020 10:45 am

Finally able to test the fuel pump. The pressure stayed at 51 psi while the engine was running but when the engine started idling rough the pressure would jump around. Since it took forever to get the fuel pump and the fuel gage was messed up I decided to go ahead with the fuel pump replacement. The people who changed the fuel pump six years ago sure boogered it up. The clamp on the filler hose was so tight it cut into the hose and stripped the clamp groves so that was a pain to get off. The evap hose clamp was broken so it was just stuck on and the clip on the electrical connection was broken off. The best part was that one of the bolts for the front fuel tank strap is cross threaded and the captive nut broke off. I'm trying to figure out how to fix that. Any Suggestions?

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smj999smj
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Postby smj999smj » Mon Apr 06, 2020 12:09 am

Tough to say without looking at it, but I would say there are two possible options. One is to get a new nut and weld it on; obviously, make sure the gas can is placed far away while welding and position the fuel lines out of the way, perhaps even placing a temporary barrier during the welding. The other would be to replace the captive nut with a regular nut and washer, if it's possible to get a wrench in there to hold it while tightening the bolt.

Twospeed
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Postby Twospeed » Tue Apr 14, 2020 8:48 am

The fuel pump didn't fix the problem, but my fuel gauge works now. I'm getting a P0300 now (random misfire) instead of a P0304. I'm going for the position sensors next. I still have to get the fuel tank sling bracket fixed. No one around here want's to attempt to fix it so I guess I buy a welder and do it myself. I've never welded with MIG before so it'll be a challenge. I have some metal to practice on before I do the actual job.

It's interesting that the fuel pump didn't fix the actual problem. The engine is starting faster with the new fuel pump. Before, it would crank for a second or two before the engine would start. Now it starts almost instantly. I also think a new starter is in my near future. It's sounded better.

Twospeed
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Re: P0304

Postby Twospeed » Sun Jul 26, 2020 1:35 pm

This turned out to be an Intake Manifold Gasket. The gasket that I put in was a paper type gasket and it failed right around cylinder 4. I replaced it with an OEM gasket and the life is back into my Pathfinder.

silverarrow27
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Re: P0304

Postby silverarrow27 » Sun Jul 26, 2020 4:39 pm

What? No details into how you discovered the leak was coming from the intake manifold?

On a serious note, thanks for the update and glad you got it resolved.

Twospeed
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Re: P0304

Postby Twospeed » Wed Aug 05, 2020 4:58 pm

Well, since replacing EVERY sensor on the engine didn't fix it I figured it was something else. ;) JK. It finally gave me a P0174, System too lean (bank 2,) so I used some TB cleaner to spray around the intake and collector and the engine nearly took off when the stream hit the manifold at number 4. Pulled the IM and the paper gasket had slipped and torn. I checked to make sure the manifold and collector hadn't warped then I put the OEM metal gaskets in and it fired right up and ran smooth. Cleared the codes and it's running better now than it ever has. It should with both new cam sensors. New crank sensor. New MAF sensor. New plugs. I should get another 200k miles now.


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