2007 4.0 p0300 code

[mwkelly]

I want to say hello and Thank You for a very informative forum. First time poster so go easy on me Please.

2007 Pathfinder 4.0 78,821, Auto, 2wd.
All filters and fluids changed at normal intervals
No issues up to this point.

Saturday vechicle starting idleing rough and miss firing . Ses light was at first flashing and then within 5 miles went solid. Had codes read and indicated a p0300. Reset and same code returned within minutes.

Wife demanded taking to dealer and was informed Tuesday #1 & 3 injector was bad. We authorised the repair.

Wife left dealer and within 25 miles same issue returned and she returned to the dealer. Dealer called today and said now #5 injector was dead and recommended " all remaing injectors replaced to avoid any other failures" Actual quote form service advisor.

I heavly questioned the root cause of this problem and was not given a ansewer. I asked about wiring issue causing left injector bank to go out, Fuel pressure , bad fuel , coils , plugs etc. All the questionable parts were functioning normal and to spec. They did know why 1& 3 went bad and now #5 was bad. The only code I saw before dropping off the truck was a p0300 and now today the advisor said it has a p0305 code.

By now every BS flag was going off in my head.

Before I let them throw more parts at the problem I would like some direction.

The parts that were replaced are:

Spark Plug #22401-5M015---They did not tell me this prior to picking up the truck
Gasket # 14032-EA200
Injector Asmy-16600-7S00A X 2

Sorry for the long post but I did not want to miss anything. Thank You Mike Kelly

[Towncivilian]

Welcome to NICO.

Is P0300 the only code?

See page EC-342 of the factory service manual for possible causes of your engine code.

Does your Pathfinder consume any oil?

[mwkelly]

Thank You.

The p0300 was the only code before the two injectors were changed. The only code present now is the p0305. The Pathfinder does not consume any oil. Thanks

[Towncivilian]

P0305 indicates a cylinder 5 misfire. Check that the spark plug coil pack's harness is plugged in completely. Also inspect all intake air plumbing for leaks - use brake cleaner or starting fluid and spray around all intake plumbing and hoses. If engine RPMs increase momentarily, you've detected a leak. Also try to ensure that the air filter is properly sealing in the air box.

Were all six spark plugs replaced by the dealer?

I checked for technical service bulletins about this issue and there are none.

[4xq]

I drop by here occasionally - as you can see, I don't post often.

Get the diagnosis of the second bad injector in writing from the dealership first thing. You may need it.

Next, you will need to confirm this, but there is an extended 8 year / 80,000 mile warranty on certain emission components, and I am almost certain that applies to fuel injectors. You posted 78k miles, so you should be ok. This may be detailed in your warranty booklet that came with the car.

After you have confirmed the emissions warranty coverage, call the dealer and tell them you want to go ahead with the warranty repair. You should get both repairs for free if I am correct. Any dealer can tell you what the extended emissions warranty is and what it covers as it is a federal mandate.

Your post makes it sound like you may need to confirm the coverages so you don't get a BS line from the dealer you are working with. Google federal extended emissions warranty to get started.

Hope that ends up saving you some coins!

[4xq]

Well, I did a little more research - I believe the 8yr / 80,000 mile warranty is on the cats and the engine computer only. The fuel injection system is 4yr / 60,000 miles.

Should have researched before I posted but it was late......

[jpar]

I am seeing P0300 on my son's Pathfinder (2001(.5) VQ35DE with 150K) with similar very rough running to the one reported here by @mwkelly . P0300 is the only code. Running VERY rich (extreme raw fuel smell, ALL plugs fouled), bank 2 shows LTFT of +25 at idle, but drops somewhat when driving at normal speeds. I have read the factory service manual (EC 315) and replaced all the obvious parts within the limits of my tools and garage: Plugs, coils, O2 sensors (MAF and air filter on order).

I took it to a local shop who charged $85 for a diagnosis, which they said included a smoke (vacuum leak) test. They found nothing, but said to replace the after-market coils with OEM, which I did. Nothing helped. The problem is no better nor any worse despite my replacements.

Seems that if the problem were a vacuum leak it would run lean, not rich. Low fuel pressure or bad injectors should also cause a lean condition.

I have seen no other codes or indications pointing to what might be causing the problem. I am afraid to drive it very far for fear of damaging the cats. The problem manifests immediately upon startup and does not improve when in closed-loop. The engine starts quickly and never stalls.

Any ideas or experiences fixing similar problems would be greatly appreciated.

[VStar650CL]

Y'all should both do a ground integrity test before going any further, especially jpar since the problem could be coil grounds. If mwkelly has a ground issue it's most likely the ECM ground wire, since the ECM grounds the injectors directly, unlike the coils which have their own transistors. On older Pathy's those grounds are usually on the RH fender behind the battery and one underneath the battery tray. They're all susceptible to severe corrosion because of proximity to the battery. To check any ground quickly, fire up the engine and set the VOM on the lowest scale, then measure from the negative post to the suspect ground connection. Any differential north of 50 millivolts (50mV, 0.05V) is trouble.

[jpar]

I had read of ground faults causing coils to fail, so I tested and found a 30mv difference from the engine to the battery negative terminal post. So I added a 12 Gauge ground wire from the engine to the battery negative terminal. This dropped the voltage to 10mv, indicating a fair amount of current flowing, but well under the 50mv you mentioned.

I will locate the grounds you mentioned (and also the F44 engine ground (EL 26) for the coils) and test them as well and post here. Thanks for the tip.

[VStar650CL]

You're most welcome! The F44 ground is usually one of a pair on 6mm (10mm head) screws right at the front of the engine, as I recall the LH side on older Pathys. The one that usually gets overlooked is under the battery pan, because the pan really has to be yanked to see it. Not all the trucks have it, but it can be real trouble on the ones that do. I've seen them completely caked with crud with no clue looking from the top. It's also impossible to check it dynamically because the battery and pan have to be out, but fortunately, if there's a crud issue it's usually obvious as soon as the pan is lifted.

[jpar]

Checked voltage to coil ground wires and several frame ground wires at the connection points to the engine and frame respectively. No problems found; all were well within expectations. I did remove and clean the coil grounds F20, F25, F43, and F44 for good measure (and because its easy). Two 10mm screws under the left O2 rear sensor plug, exactly where you said they would be.

Now to pull the battery and pan may take a few minutes....

Thanks again.

[VStar650CL]

Yep. I don't have ASIST in front of me on a Sunday to confirm it, but 95% of the time that one under the battery is the main ECM ground. It's a butt-pain, but you ignore it at your peril. When I find corroded ones I generally hit them with 2 coats of galvanic battery terminal paint, to make sure they won't give my customer trouble again soon.

[jpar]

On this model the battery tray is welded and there are no wires underneath. However I was able to trace the battery ground wire and access it, so I removed, cleaned, and reattached it with dielectric grease. Also cleaned up the battery terminals. Although I still don't know the problem or the solution, I can now add grounding to my growing list of things that it isn't.

[VStar650CL]

The #5 plug can generally be removed without a lot of screwing around, have you taken a look at it? The color and condition will at least give you an idea whether the problem is rich or lean.

[jpar]

I replaced all of the plugs last week, along with the coils (again). They all were black with carbon deposits. The strong smell of raw fuel, even when warmed up seems also to indicate it is running too rich.

[VStar650CL]

Since it isn't lean (which could be a blockage), the only thing all the injectors on the bank have in common is the 12V rail and I think a subharness connection. There will be a single harness branch that supplies 12V to all 3, and if I recall correctly, a wire-to-wire connection buried on the LF of the engine. Sounds like you have the WD for it, I'd locate and check the connector for crud, and if you can reach one, see if the 12V to the injectors is solid. Has to be some common factor for all three to fail on the same bank, it can't be plumbing.

[VStar650CL]

Identifix confirmed it, there's a subharness on the Bank1 side of the engine (Bank2 connections are all direct to the ECM). Connector F44 in the EGI harness to F110 in the subharness, can't recall if it's at the front or rear of the engine on 4L's but it's where the injector wires duck under the plenum. The W/G wire on both sides is the 12V supply. Check voltage at the EGI side and if okay, check voltage drop across the connector while running. Poor power contacts will leave the high-voltage "kick" from the injector coils with noplace to dissipate and will heat up the injectors, could cause them all to be failing on that bank.

[jpar]

I have been offline for a very busy work week and only now getting back with an update.

New MAF received and installed - changed nothing.
I retraced my steps to when the problem started. This was an intermittent problem until I replaced all the coils. Replacing the #4 coil required removing the throttle body. While I had it off I decided to clean it. I used brake parts cleaner and a toothbrush. It did not come completely clean but looked much better than before.

So I was thinking, maybe something went wrong with the cleaning; maybe I created a leak that would let coolant into the intake air stream. I did a search and found this article on this forum about bypassing the coolant to the TB. how-to-bypass-coolant-line-in-throttle- ... 33725.html

So I tried that, with high hopes. But again, it changed nothing; all is exactly as before.

Did I say it is running rich? It is so rich that I dare not start it in the garage, and it actually drips raw fuel from the tailpipe.

I located the connector that feeds the injectors (and the knock sensor). It is a dark blue, 8-position connector (called L/8, F5 to F100) with 7 wires. I disconnected it. Looks clean, no problem there.

After 4 weekends tinkering with this, the problem continues exactly as before.

[jpar]

BTW, I probably should have started a new thread for this one. This car is a 2001(.5) Pathfinder LE 2WD with a VQ35DE with 150K miles, but the problem is the same as the subject line for this post, P0300 is the only code, running very rough, very rich.

[VStar650CL]

If there's fuel dripping out the pipe then something is stuck wide open all the time, maybe more than one something. Have you tried a power balance test to see if any of the cylinders don't respond? If an injector is stuck wide open or has a grounded low-side wire, the cylinder won't "dead miss" because it has fuel, but when the power balance tries to shut the injector down, nothing will change. So you'll see an RPM drop on cylinders with good injectors but none on a cylinder with a leaking injector. If the problem is a leaker, you can't duplicate it with a "poor man's" power balance by disconnecting coils, the cylinder will show a drop when the coil is pulled because the issue is too much fuel and not lack of spark.

[jpar]

I would like to do a power balance test. I have Torque Pro and a Bluetooth connector which will provide only read access. I downloaded and installed the Advanced EX Nissan plugin (https://play.google.com/store/apps/deta ... n_US&gl=US ) which includes many Nissan models, including the Maxima with the VQ35DE engine, but not the Pathfinder with that engine. I am hesitant to try software written for a different model, as it could cause damage.

Back in 2010, when I bought the car, I bought the blaZt software and adapter cable (RS232). I used it for years to troubleshoot various issues and it was very effective. But they went out of business years ago and off the grid, at least by that name. Does anyone know of a modern equivalent that works with the 'standard' Bluetooth adapters?

It is looking more like a fuel injector issue. Here's a very informative post about stuck injectors: gas-coming-out-of-tailpipe-t435389.html
But I'm not seeing a vapor trail yet. And it is possible that the dripping from the tailpipe is condensed water mixed with unburned fuel. The injectors are hidden under the manifold collectors; I cannot even get to the connectors.

Should I order a set of after-market injectors ($65 for a set of 6) or get the OEM? I found a set of remanufactured Bosh OEM on ebay for $60.
I will also need a gasket set for the intake manifold collectors. Should I plan to replace the leaking valve cover gaskets while I am in there?

Is there a good 'how to' instructions for this job?
What is the best way to relieve the fuel pressure before disassembly? remove fuel pump fuses and run the car until it stalls? Or is it better to remove the relay?

[VStar650CL]

Whew, that's a lot of questions. Obviously I use a CONSULT3+ at the dealership, but most high-end scanners have power-balance in the work-support options. Choice of injectors is up to you, reputable remans are usually okay but the "usually" can bite your butt. Make sure the seal rings are new regardless, and make sure you lube them lightly with vaseline before insertion. Always use new gaskets, no matter what sort of repair you're talking about. Gaskets are cheap and your time isn't, nothing sucks worse than re-doing 4 hours' work over a $0.50 piece of rubber. Since the plenum has to come off anyway, by all means replace your leaky VC's (and plugs too if it hasn't had any recently) while you're in there. The easiest way to relieve fuel pressure without using a scanner is pull the fuel pump fuse and run it dry.

[VStar650CL]

PS - An injector drive wire shorted to ground can cause a wide-open condition too, so once the plenum is off, disconnect the ECM and ohm all the drive wires to ground. They should read infinity or close to it. If you find a low reading then the harness has an issue and not the injector. The drive side is easy to identify, it will be a different color wire on each injector in the bank. The 12V supply wires will be the same color across the bank.

[jpar]

OK finally a happy update. 2001 Pathfinder is fixed and running fine. Your recommendation to do a power-balance got me thinking. One, that it should have been included in the 'diagnosis' I recently paid a local shop to do (they recommended replacing the coils which I had just replaced, with OEM coils, which was a waste) and two, that I could probably do one myself by disconnecting the coils one-by-one (poor-man's power-balance test). In preparing for the test, I looked to see how I would get to cylinder 4 coil which is directly under the throttle-body on this model. I noticed that cylinder 4 and 6 coil connectors point in opposite directions and are less than an inch apart. Hmm....the problem started after I replaced all six coils. Could I have switched 4 and 6? I was always very careful. After searching through the various shop manuals, I finally found the color coding for the coil wires in the EC manual, page 492. And sure enough, wire 6 was connected to 4 and vice/versa. After kicking myself numerous times, and switching them back, the car now purrs like a kitten.
What is amazing is that it ran at all with this serious of a problem. Anyway here's another one for the troubleshooting books. And I will write the cyl# on each connector from now on before doing any disassembly.

Thinking back, all the symptoms make sense now. Two cylinders getting fuel, but not burning it; ECU not detecting and shutting off fuel - saw only random misfires. AND a power-balance test would have identified this quite easily. Maybe I'll ask for a high-end scanner for Christmas.
Anyway, the plugs, coils, O2 and MAF sensors probably were due for replacement anyway. Should be good for another 150K miles now.

Thank you so much for all your analysis and advice. It was spot-on.

[VStar650CL]

So glad you got it straightened out. Several attaboys, well done!