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Oil Loss Issue


cham
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I've had my 02 patty for about 2 years and ever since I can remember it's had some oil loss problems but more recently has it been getting unbearable. I'm the 2nd owner and I believe the first might have sold the truck knowing it was going to get worse. Regardless, I'm having to fill half a quart around every 2 weeks at the least. I've switched to synthetic fairly recently, around 5 months ago, its not until more recently has this problem become bad. Checking for leaks there is nothing I can see, especially for the amount that is lost. I'm stumped though because I have not seen any soot or black smoke coming out of the exhaust, or even smoke for that matter. I've even had other people look at it while I drive. This is completely separate from my decline in acceleration problems which I believe is somehow linked but not totally sure. So after scowering the internet I've come across the possibility of the reason being because of a failing PCV valve or valve cover. I've heard of there being an updated system put out by Nissan that essentially fixes the common oil burning issue from pathfinders but I have no idea where to find this or even explain to a mechanic this idea without sounding crazy. I'm also wondering if I should get my spark plugs and ignition coils looked at as well when I finally do get the truck into a shop for the oil because I believe they are greatly affected by the constant burning of oil. In another regard I'd like to fix the source of the oil issue first so that I am not showing up in the shop for the same plugs over and over again. I'm basically lost as to where to start and maybe get an idea in how much this fix might cost. I really love this truck and would do a lot to keep it in its happier years for a little longer but if it's too astronomical it might not be worth. Also forgot mention that I have a Vyncs Reader in my OBD2 scanner port for many purposes and I keep getting the error notification of poor fuel economy and another error saying engine fuel lean but it seems to only appear occasionally. Don't know if this helps but I thought it might be helpful to mention anyways.

Edited by cham
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Mine had been losing oil fairly rapidly, and I could smell burning oil at stoplights. But there was no indication of the engine burning the oil on the spark plugs, or tailpipe.

 

The 1st mechanic thought it was the valve covers leaking, and he replaced the gaskets. This helped a good bit, but not completely. I took it to a 2nd mechanic for a 2nd opinion, who re-torqued the covers (commonly necessary), and told me that I did have some leaks around the oil pan, and a weeping main seal. He didn't feel like those were worth addressing. I didn't ask for a quote on either of those, but he said if I ever need to replace the clutch, that would be the time to do the main seal too.

 

Now I'm down to losing 1 qt every 1,000 miles, which is tolerable for me. Fortunately it doesn't seem to leak in the driveway. And I haven't smelled burning oil at stoplights the few times it has been cool enough to have the windows down. But the real test of that will come in the fall.

 

Finally if you have an automatic, I'd check the oil cooler gaskets, which are very common leak points. There is at least one post on this forum about it. I don't remember reading about the PCV TSB from Nissan you mentioned.

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I forgot to address your power and error code issues. What are the actual error codes? I'm not aware of a low fuel economy one.

 

The very first thing I'd do is replace your fuel filter, and check your spark plugs. I was having an intermittently rough running engine, with occasionally a specific cylinder misfire code. I was convinced it couldn't be my spark plugs, because they should have 40k miles of life left. I had already bought $350 worth of coils, fairly convinced that was what it would be. Turns out I forgot I had to replace the spark plugs with lesser quality ones. They were 10k over their predicted life, and were in bad shape.

 

If you are actually burning oil, it will be obvious on your plugs. But this shouldn't have hurt your coils.

 

Next I'd look carefully around all the rubber hoses and air intake on your truck. Mine are getting cracks, and I've had to replace or repair them. This would definitely lead to lean running.

 

After that, I'd suspect a failing fuel pump, and would figure out a way to check the fuel pressure before spending the time/money to replace it.

 

Finally I'd suspect either an 02 sensor or MAF sensor. But those I would expect to have error codes to lead you in that direction.

 

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This is starting to make a little more sense. I'm starting to think my spark plugs are at the end of their lifetime. With the addition of a known oil loss issue more likely burning, its a no brainer to get them checked out. I actually replaced my fuel filter around a year ago and I believe it should still be in okay shape. Is there a chance it could have gone bad though before it's expected lifetime? The metal clamp I mounted it back into is all bent up from a frozen rusty nut that took forever to remove, but something like that wouldn't cause it to fail I hope. I also had one of my 02 sensors replaced around half a year ago after it failed but I can't remember exactly which bank it was. Now going back to what you said about the valve cover, how come the 2nd mechanic wanted to re torqued it after having already gotten the gasket replaced? Do the valve covers cause burning or leaking when not tightened correctly? Also what is the cost for something along those lines, possibly also replacing the pcv valve while they're at it because it's a common fail point and it's so close to the valve cover? Finally, the error codes are not actual codes thrown by the vehicle. I have a Vyncs reader that stays in my OBD 2 port all the time giving me information about my car via app. Occasionally it'll send me a notification of low fuel economy or engine fuel system lean but the parameters of this device could be so close to the normal range that these are basically within the normal limits of the car. There are a plethora of possibilities though as to why my car would be running lean, but could it be due to fuel filter having gone bad? I know having a system running fuel lean definitely has an impact on performance. Sorry for asking so many questions in no particular order that makes sense by the way, I'm just kind of saying everything that comes to mind first.

 

 

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Edited by cham
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Burning oil may be fouling plugs. Coils should be unaffected; also, the ECU should code if a coil is failing. Oil can leak past loose gaskets just like it can leak past shot ones, so it's possible your mechanic wanted to double-check the last guy's work. A fuel filter bad in a year is unlikely, unless there's rust or other junk in the tank. (The bracket should have no effect.) Unless the truck sat for a long time with gas in the tank, or you replaced the filter because the last one clogged up, I doubt the filter is your problem. Though a clogged filter could certainly cause a lean burn, I'd expect the ECU to code for that (though I don't know the R50 ECU well). If you suspect a lean condition, I'd have a look around for bad vac lines or intake gaskets (and the rubber pipe from the engine to the air filter box). I'm also not sure I'd trust your OBD whatsit over the factory ECU--it could be kicking out the lean warning when you're engine braking and the ECU cuts fuel. When you pull the plugs, take a look at the ends of them; if the truck is running lean, the plugs will be white.

 

That said... my dad had an '03. No visible leaks. Sucked down a quart every 1k (so he was adding oil weekly). Smoked like a mofo on warm starts, but never any other time. He too ran synthetic, but only because the smoke was less dense on synth than it was on dino. Had the PCV changed, didn't seem to change anything. Might've been rings, might've been valve seals, we never tore into it to find out. He sold it to a guy who had a rebuilt 3.5 ready to go. Strangely enough, it never seemed down on power.

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Yeah i started college last fall so likely it had been sitting for extended periods of time with out being used. Maybe my parents occasionally used it but not very much if any since it sat in the garage. How long is long though, I might just replace the filter anyways since it's fairly cheap and it rules out this as a possibility. Now I actually noticed something interesting today, I tried looking for a vacuum leak and through all the infinite number of hoses, (visually inspecting the engine is pretty much a lost cause for me) it seems like I hear a pretty sizable amount of air escaping somewhere closer to the driver side behind the engine. Now there's no way of telling if it really is a leak or just my imagination created by the fan or engine but to me it seems like it's separate from the rest of the commotion going on. I've always heard a very high pitch ringing since I've had the car but not necessarily coming from the engine though I heard this is a symptom of a vacuum leak. I can't tell where it's coming from due to the nature of a high pitch sound but more likely then not it sounds like it would be some tiny air leak coming from some part of the exhaust manifold. I've looked under my car and it's a rusty piece, all along, but just giving it a quick once over I can't find any particularly noticeable leaks. As for the spark plugs, I definitely should get them looked at but I just don't want to spend the money on getting them fixed and then proceeding to burn oil, ruining them at a much quicker rate than they should normal ware.

 

 

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Honestly if it didn't sit for, like, ten years, in a swamp, and start having fuel pressure issues just after you got it going again, the tank's probably fine. A year or less shouldn't hurt much of anything. That said, fuel filters are cheap, and you could cut the old one open and see if there's anything caught in it. None of the fuel filters I've opened up had much of anything in them. You could also pull the fuel pump and look down into the tank with a flashlight to see if there's crap in there that shouldn't be.

 

Vac leaks can be a real pain to track down. I'm not sure about ringing, but a whistle could be a vac leak. You could track down a vacuum routing diagram and just follow each line (as far as you can), or hook it up to a smoke machine, which makes smoke pour out of any openings that aren't supposed to be there. If you suspect you've found the leak, you can spray a little carb cleaner at that spot to see if the engine idle increases. You might also take a look at your MAF sensor. A dirty MAF will tell the computer there's less air flow than there is, again causing a lean condition.

 

If you can do the plugs yourself, you could always just pull a plug, look at it to see if it's obviously worn out or fouled, and then put it back if it's not.

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I'm guessing there's most likely some sort of vac leak but finding it on my own with the tools I have would be a real task. How is it you would go about cleaning the MAF sensor, I'm guessing it's a process of taking off the intake rubber pipe and looking inside? Also are taking the plugs out something that is possible without having to take apart everything including the plenum and such? Have you done it yourself?

 

 

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Looked around my ignition coil locations and I noticed on the drivers side, it seems like all 3 have a oily residue caked around the outside on the surface, not on the coils but on he surface of the body surrounding where the ignition could sit in the engine. Take note I have not tried to remove hen to check the spark plugs yet. I'm wondering if this means theres something entirely wrong? I know I have spilt some oil over the sides of the oil filler hole when refilling occasionally but this only exists above the one ignition coil, I doubt it would have spread to all 3 on that side of the engine.

 

 

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The MAF is the thing between the air filter box and the rubber pipe going to the throttle body. It's delicate, so be careful with it. You can get spray MAF cleaner, but really any cleaner that doesn't leave a residue will work. I cleaned mine with alcohol and the corner of a rag in a hotel parking garage once and it turned out alright. There's probably a how-to on Youtube somewhere.

 

I haven't wrenched on a VQ so I don't know all of what's in your way. I wouldn't worry too much about a little oil on the coil packs. If you pull them and the plug wells have a bunch of oil in them, either you spill more than you think or the seals between the spark plug wells and the valve covers aren't doing their jobs. Either way, not the end of the world.

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Okay that makes me feel a whole lot better. I appreciate all of the info and I might just take it to a mechanic to get a definite diagnostic rather then fiddling around with it myself. I've gotten the maf cleaner and will be doing that soon, I'll then probably hand it off to the professionals for the rest. Would you happen to have any idea how much getting the valve cover gasket replaced or tightened might set me back? Also having them use a smoke machine to try and find a vacuum leak I can't imagine would be that expensive unless I'm wrong. I also noticed that the exhaust is pulsating in the slightest manner, not a constant stream of exhaust which leads me to believe that there might be a misfire but within the computer threshold that will set off a code because my dash shows none.

 

 

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Hopefully the MAF cleaning helps! Take your time and be gentle, it's not a hard job but it's not a cheap part.

According to this writeup (minus pics unfortunately because Photobucket), the plugs aren't too bad to get to, so I'd start there. If the plug wells turn out to be full of oil, then yeah, the gaskets may have a problem; also, oil-filled spark plug wells can apparently cause a misfire, so you might kill two birds with one stone there. (No idea on cost, sorry.) If the wells are fine, leave the gaskets alone and move on to checking other things. If I found oil in the plugs near the oil filler, I'd clean it out, put it back together, and take it apart again after a while to see if the oil had returned (leakage) or if it was just there because you spilled while filling it. I assume there's some kind of o-ring on the injector to prevent outside spills from getting in (to keep dirt out if nothing else) but like I said, I haven't had a VQ to bits.

I assume a mechanic would consider the smoke test diagnostic time, and just bill you for how long it took--but I've never had one done so I wouldn't know.

 

If the mechanic has to take the intake apart (which I assume is required to get to the covers), you might as well have the power valve screws loctited at the same time. Some people have had those back out and fall in. Small amount of added work that could prevent trouble down the road.

Edited by Slartibartfast
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Something to report, the same day after I had cleaned the MAF sensor the way many videos in YouTube explain explain it, later in the day my service engine soon light came on. The following day it remained on for quite a while and eventually turned off on its own without reshowing since. Looking on the Vyncs app when the code was actually there it mentioned "Evap system leaking (gross leak). It seems to have fixed itself though and I don't know if I should be worried.

 

 

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Evap leak can be anything from a torn filler hose to the evap valves getting flaky to the gas cap not screwed on right. Personally I'd ignore it until you've got the other issues figured out. I'd be surprised if it was related to the MAF cleaning.

 

Any improvement from a clean MAF?

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