My repair that is making things worse! p0420 Code - Nissan Murano Forum
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post #1 of 17 Old 02-19-2018, 11:48 PM Thread Starter
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My repair that is making things worse! p0420 Code

Hello everyone! I have only had my Murano for maybe a month or two, but I am not stranger to Nissan. I work a lot on my 1994 300zx TT, but I leave that in the garage in the winter and I am finding that working on this newer Murano is much more difficult than even the Z that people say is the worst.
The car is a 2005 Murano SL AWD. I received it from a family member who mentioned that he did not want to keep up with its oil consumption so I got a good deal on it. It seems to drive great, no issues that I can tell even in the snow up in the mountains with some studded snow tires I got for it.

So far I have Changed the oil and filter and Changed rear PCV (It was recommended that this is the one to change for oil consumption issues) and I installed a catch can on that line to see how much oil was getting sucked in that way. I verified the catch can sealed well and had media for the oil vapor to collect on just in case. It has remained empty for maybe 300+ miles, though I work from home so I don't drive it that much.

The car almost always smells like burning oil inside. I freaked out thinking that it could be the transfer case/CVT seal right above the exhaust like some people have an issue with. I didn't see much of an active leak on the TC, just a little MILD wetness where the fill and drain plugs are, not fresh. I plan to drain and refill the Transfer Case with the Redline GL-5 75w-90 gear oil I used for the Z32's rear diff. I know on my manual trans in the Z I have to make sure to use GL-4 as GL-5 will eat the softer metal on the synchros. I don't think that is an issue here with the transfer case but I had a hard time finding an answer to that question anywhere. I did see a leak on the CVT side at the axle. I attached a picture that I scaled down to get it to attach. It looks like the CVT to CV Joint seal. I checked the CVT oil according to instructions by warming it up on the street and then selecting each gear and then back to park with the engine on I checked it. It was EXACTLY at the hot notch. So if it is a leak, how is my fluid level so perfect? It would have to be a really small one. The only other fluid leaks are the power steering hose like like every Nissan I have ever owned and possibly the rear valve covers, though I am not sure since I haven't taken the intake manifold off too look, I only looked at the small corner of it and it seemed like it was moist.

I received a P0420 code a couple days ago, which is the catalytic converter below threshold. I got worried because I know that they way Nissan does their valve timing (Mostly an issue on the 2.5 liter, but i heard it can happen on the VQ), it could get pieces of the catalytic converter into the cylinder and screw it up. So I took off both converters and noticed that the one nearest to the firewall was falling apart, sliding down in the housing where it was supposed to sit. While I did this repair I had to remove the heat shield on the front exhaust manifold. One of the bolts that held it on was really close to the low pressure line for the AC. I BARELY bumped it and wouldn't you know it, all the coolant leaked out of the connection between the hose and the compressor. Is this a common issue? Did I break something? I barely moved it. I will buy a new hose if need be, but the bolt that held it on is still tight. Maybe it bent? I don't know.

Maybe the oil burning smell is only from a bad rear valve cover gasket. I didn't want to pull the manifold but I do have the gasket if that is not reusable, I just need to find the procedure for this somewhere when I get the motivation. I have new plugs to put in when I do.

Thanks for reading my rant and ramblings.Any advice you can give to to restore my sense of accomplishment on this? I appreciate it!
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post #2 of 17 Old 02-20-2018, 12:13 PM
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The leak on the photo is probably the axle seal. I have replaced that seal long ago and you will need a couple of quarts of NS2 CVT FLUID to replenish the one that will flow out once you pull out the left axle. There are threads on this.

I don't understand what you broke that caused a coolant leak. Is it green coolant that spilled or is it the refrigerant from the ac?

Did you replace the cat converter on bank 1-firewall side? If its rattling from the inside when you shake it, it needs replacement before frags gets sucked back into your engine. You can try the antifouler trick to fix your P0420 code.

Have you replaced the PS hose that was leaking?

If you have multiple leaks going on, you have to fix them all to eliminate the oil smell you are having inside the cabin.

There is a good thread on how to replace the spark plugs and the rocker cover. Check the sticky.
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post #3 of 17 Old 02-20-2018, 01:40 PM
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It does appear to be the axle seal. I replaced mine with an OEM seal from Nissan for $12. I then purchase a PVC fitting for $0.98 from Home Depot to punch the new one in evenly. Also, if you lift just the left side of the car, you shouldnít have any fluid leak and/or need to purchase additional fluid to replace (Iím almost positive on this one, as Iíve recently replaced my front left axle).

On the other hand, I fixed my P0420 code with the spark plug no fouler mod. Purchased from Atuozone for $5, drilled a 1Ē hole in one of the fittings and screwed everything into the exhaust. There are plenty of videos of this on YouTube and it does work to eliminate the code. I also increased my gas mileage by about 3 MPGs.

As far as leaks, if it is a PS hose leaking, it will burn up by dripping down on the exhaust and have a significant smell to it. I would watch your driveway and/or PS reservoir level, as this leak does tend to increase in size over time.
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post #4 of 17 Old 02-20-2018, 02:11 PM Thread Starter
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Oh, thanks for the response! Yeah the leak that I smell burning must be coming from somewhere other than the TC thank god, but the AC refrigerant (r134a?) leaked out at the low pressure hose to compressor connection, the one with the single bolt below the line. I barely touched the line and it started leaking at the connection. The PS leak was "fixed" at a repair shop by the previous owner apparently so it probably has a warranty still. I will attempt the fix on the valve covers after I finish up the cats. I am just gutting them and using a spacer on the O2 and I might try the fix where you take a 1 Mega Ohm resistor and 1 micro farad capacitor to fool the ECU. I don't want to chance a new cat getting messed up again prematurely due to the oil consumption, if it is still present. Plus as far as I have heard the precats are mostly for cold engine emissions and the secondary cat will be sufficient when the vehicle is warm. It isn't worth the risk of ruining the engine over cold engine emissions imo even if it is a remote possibility.

I am most annoyed that the AC line leaked, I assume I need a new one but it really didn't take much to ruin this one and I will need it recharged now too :/ Any advice on that part of it?
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post #5 of 17 Old 02-20-2018, 05:17 PM
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Not sure which part of the low pressure AC system is broken, but, you can get a replacement for it and buy yourself a vacuum pump(HF $76 with 20% off), AC gauges(HF $48 wtih 20% off) , plain refrigerant- no sealers and recharge your own AC system to specified 134-a weight. Or fix the broken part and pay at least 100 bucks to have an auto ac place recharge the system up for you. Your call.

The antifouler for the O2 sensor should be enough to trick the computer and fix your P0420. Just be sure the old CAT is not rattling from the inside otherwise it'll be an even bigger trouble. I know they are expensive even the aftermarket ones but if you have smog in your state then its a must.

My 04 has been burning oil that started around its 3rd year. @118K now, it burns maybe around 1 1/2 quart every 6-7K OCI.
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post #6 of 17 Old 03-04-2018, 10:39 AM
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@AsdfMan

I had the same problem. Oil disappearing rather fast with no oil on the ground or blue smoke from the tail pipe. I could always smell burning oil. What your going to find is cylinder #5 (by the firewall right in front of the driver) is the culprit. What is happening is the spark plug tube is filling up with oil due to a dried up seal in the valve cover that the coil pack goes through. You can find threads on this forum confirming this.

On top of the valve covers you find one coil pack for each cylinder. Each of these coil packs pass through the valve cover, in a metal tube and click onto the spark plugs. The rubber seals around the spark plug tubes harden and fail to keep engine oil from entering the tube. The tube will fill up with oil hence, no oil on the ground. It's being contained inside the tube. The tube being metal it gets very hot! So, you have engine oil leaking past a valve cover seal into a very hot, metal, spark plug tube. The heat of the metal tube slowly burns the leaked oil off hence, the constant smell of burning oil without seeing any smoke. The rubber seals in the valve covers are machined into the valve covers and can not be replaced by themselves. The entire valve cover has to be replaced when the seals go bad.

Like I said you can find threads here backing this up and with more info a can't remember. Hope that helps you as I am sure it's your problem.

Good luck,

Koda
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post #7 of 17 Old 03-07-2018, 04:29 PM Thread Starter
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Great Advice

Thanks for the advice on the spark plug tubes. I purchased new valve covers to install as well because I noticed from under the car when I gutted the cats and changed the TC fluid that there was a drop of oil on the seal between the valve cover and the head. I think replacing the covers with new ones with new seal included will fix that.

I Purchased the vacuum pump and AC gauges as a kit for adding the r134a with my new AC hose. I don't think much of the lubricant leaked out (PEG100), but I plan to add a little as it appeared a bit did leak out since it was right next to the compressor. I will do that last since the hose connection is so delicate.

I finished the cat gutting and it went well. I started the car and it seems quiet, and I did get all new exhaust o-ring gaskets. I had to add silicone copper RTV for an exhaust gasket on the front pre-cat to manifold connection because the o-ring seal there seemed to sit against the catalyst material itself and with it removed the o-ring just fell through. My fix seems to hold though and no leaks.

After I was done and accounted for all the bolts (Including the one I snapped in half and had to drill out and through bolt it ) I noticed a bracket/ protector thing in the picture attached. I don.t know where this went/ anyone have an idea? Other than that, I only have the valve covers/seals, spark plugs, PCV (double check since I just changed it), AC line replacement and recharge, CVT drain (then replace the leaking transmission seal on drivers side) and refill.
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post #8 of 17 Old 03-10-2018, 12:07 AM Thread Starter
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Ugh!

I just replaced the CV shaft to transmission seal and I drained all the fluid and refilled with the correct fluid (NS-2) and it was pretty brown. After filling I drove it around the block a bit and it was EXACTLY on the hot notch. I considered this good and then ran an errand and came back. I checked the fluid level again and it is like the image. I don't understand how it could be overfilled because I put the exact amount back in that I took out (5.5 liters) or 5.8 quarts. Should I remove some fluid or is this good? I don't want to damage anything . I followed the FSM for checking the fluid verbatim and made sure to select each gear before checking.
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post #9 of 17 Old 03-10-2018, 10:49 AM
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I think you're referring to #1 as before and #2 as after, right?

#2 still looks slightly low to me, but it's hard to see any markings other than the "hot notch".

One thing about checking levels is that "around the block" isn't nearly enough to heat up the transmission. 5-10 miles of driving should do it. I think your measurement after 15+ minutes of driving is moer accurate and probably reflects the level with warmed-up transmission moer accurately.

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still looks slightly low to me, but it's hard to see any markings other than the "hot notch".

One thing about checking levels is that "around the block" isn't nearly enough to heat up the transmission. 5-10 miles of driving should do it. I think your measurement after 15+ minutes of driving is moer accurate and probably reflects the level with warmed-up transmission moer accurately.
That makes sense. The red line shows fluid level since the fluid is too transparent to be picked up on camera well. If that line is the fluid level, should I drain some? I refilled is EXACTLY what I took out though...
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post #11 of 17 Old 03-10-2018, 12:44 PM
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I looked at the pictures again and it appears the red line is in two different places relative to the notch.

I'm on the fence about this. I don't know how much it would take to get to that mark, and I'd be less concerned about the mark in #1 than in #2 , because it appears to be much closer to the notch. If you're 1/2 quart or less overfull., I would doubt there's a problem...and that seems like the most likely scenario. If you were a quart or more overfull, I'd be more concerned about oil getting air whipped into it mechanically.

If you can do it without undue fuss, it probably wouldn't hurt to drain out a bit.

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post #12 of 17 Old 03-10-2018, 03:11 PM
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I just replaced the CV shaft to transmission seal and I drained all the fluid and refilled with the correct fluid (NS-2) and it was pretty brown. After filling I drove it around the block a bit and it was EXACTLY on the hot notch. I considered this good and then ran an errand and came back. I checked the fluid level again and it is like the image. I don't understand how it could be overfilled because I put the exact amount back in that I took out (5.5 liters) or 5.8 quarts. Should I remove some fluid or is this good? I don't want to damage anything . I followed the FSM for checking the fluid verbatim and made sure to select each gear before checking.

Was the fluid level in the right spot on the dipstick prior to you draining and replacing? If so, don’t drain just yet. Drive the car more than just around the block and let all of the cavities in the CVT fill up with fluid.

As long as the level was good previously and you put in the exact amount as you stated, make no changes at this point. It would be impossible to have any different amount, as long as your readings were EXACT prior to draining/during filling.
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post #13 of 17 Old 03-13-2018, 03:32 PM Thread Starter
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Yes, I am sure my measurements were exact. I drained the fluid into a clean oil pan and used a hand pump to pump it into a measuring container one liter at a time to get EXACTLY 5.5 liters. I then filled the trans with that exact amount. I measured the fluid with a cold transmission with the engine on after selecting each gear and it was on the cold notch EXACTLY. However, when I drive it around and get it as hot as I can (did this a few times) it sits at either the H or the O on HOT depending on the ambient air temp here. Should I drain some to make it sit on the upper notch when hot? It would then sit below the notch when cold I would think since it is right on it now. So I don't know if that is bad or not.

Another note, I found that the axle seal that I replaced is leaking about the same as it did before. It really only drips when hot and I park it. I tested this by parking it on top of a cardboard piece since I was paranoid and checked. I found that it does certainly drip. Could this be because the axle input shaft is worn and does not seal well against the trans seal? The old seal that I removed looked OK but I replaced it anyway. When I replaced the seal I used a seal puller with no trouble and used an actual seal press tool that I purchased specifically to install it without damaging it, so doubt that it was damaged in installation, but these things can happen. It wasn't a tough job but I don't want to keep doing it if the problem isn't the seal.

I did finish the valve cover replacement, PCV replacement and spark plug replacement yesterday though and so far after testing, that has worked out great! Thanks for the help everyone!
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post #14 of 17 Old 03-14-2018, 01:54 PM
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Another note, I found that the axle seal that I replaced is leaking about the same as it did before. It really only drips when hot and I park it. I tested this by parking it on top of a cardboard piece since I was paranoid and checked. I found that it does certainly drip. Could this be because the axle input shaft is worn and does not seal well against the trans seal?
Sorry Iím not itís sure if you mentioned whether you were the original owner, or if the axles were ever touched by a shop. Anyways, if the seal was installed correctly, which I would assume that it was, I would say that either the shaft itself has been hit and slightly damaged, or something isnít lining up properly, causing the leak. I would pinpoint the leak location to determine whether itís leaking from inside the sealís ring (where the shaft slides into) or outside of the seal ring (which touches the trans itself).
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Thanks for the response. I think I may have goofed when I installed the seal. I pressed the seal all the way in and according to some DIY videos and illustrations, the main part of the seal body is meant to sit flush with the transmission. I pressed it in until it was seated all the way in, beyond flush. I think this is my leak. I will redo it this week and see, but others have mentioned a leak here on other FWD cars, I would think this CV joint is no exception. Otherwise I will probably have to get a new CV shaft and try that if it keep leaking.


Any thoughts on the fluid levels vs temperature? I am confused when the cold is spot on but the hot is too high.
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