R50 acceleration problems

[cham]

Let me begin to say that I have little to no knowledge on vehicle engines and vehicles in general. The extent of my knowledge goes about as far as changing the oil . Anyways getting to the actual problems, I purchased a 2002 auto trans pathfinder LE from a private owner a little over a year ago. He had all the records of the past maintenance and such so it seemed like a good gig. I also wouldn't begin to say that the truck was not worth the money I paid, I've just been having some frustrating problems with it pretty much since I've owned it. Looking back at when I first test drove it, it seemed like it had more power and faster acceleration. Now after about a year I notice that it feels like its lost compression and struggles to get up to highway speeds at a constant rate. On a side note, the shifting of gears lags a little bit. When turning into oncoming traffic, if I try to accelerate at a decent rate it will almost jump it feels like in between shifts. Besides that point ever since I can remember it roars. From the very start of owning it though I heard this was normal for pathfinders so I kind of shrugged it off, but the thing is loud. My parents know when I've turned on our street if they're outside just from me driving up a slight inclined road in our neighborhood because the engine or fan is so loud. When I start up the car from cold it'll be at a moderate level until about 30 seconds into it it'll start to roar. On further investigation this, if I'm correct, is normal because it's just a way for the car to warm itself up. After about a minute or 2 after startup, the noise level drops as do the rpms from about 1400 to just under 1000. Now this is all fine and dandy but when I actually drive the thing, upon acceleration the engine still roars really loud. I've heard this could be that the fan clutch has too much resistance and its turning at the same rpms as the engine but I have no actual proof of it. As for the acceleration and slow shifting, I checked the transmission fluid and it seems to be nice and at a good level. One last problem I've been dealing with for the past year is it's oil. If I can remember correctly after a few months of owning the thing my dad and I realized that it was somehow losing oil at a substantial rate and still is to this day only worse. Our original thoughts were that it was an old car and burns oil as do many old cars but more recently I just found out it was leaking oil. This seems to have happened relatively within the same time frame as getting the oil changed with synthetic which my dad says is why it's leaking now. I have no idea if he's right but that's why I am here. It could be that we just seemed to notice it leaking because for the first time we actually parked it in the garage and of course that will show signs of leakage. Whether its leaking or burning oil could this be some of the reason for my many other problems. As best I can I try to keep the oil at a solid level but sometimes it'll get really low without me noticing, especially since I'm in college right now and cant always be home to check it with my parents using it every so often. In between oil changes in total on average ill probably end having to add 2 quarts. Probably more now with the recent knowledge of it leaking. If anyone has had the same problems before and can possibly diagnose any sort of culprit it would be much appreciated. Thanks.

[Cuong Nguyen]

First off, check for codes and start there. That's a lot of oil to be losing. Burning oil will eventually clog your cats. Fast. This will cause performance issues as its creating excessive backpressure. If there is any leaking, the rear main seal along with the valve covers is very common due to the rubber seals drying up and shrinking.

 

Roaring if the fan is signs of a seized fan clutch. You can spin the fan by hand and see if it spins a little . If it does you're OK. It should have sought resistance. If it doesn't spin or is really hard to spin that means it's sticking. A stuck fan clutch will suck a lot of power from the motor and make it loud.

[LittleFR]

If it leaks on synthetic switch back to conventional. The molecules in synthetic are smaller and can leak easier, I had a Ford truck that never leaked a drop till I put synthetic in it.. Ran conventional two changes and it quit again.

 

Do a flush and fill on trans, pulling the dipstick isn't a real indicator of the oil condition, mine looked cherry red on the dip... When I changed it, it looked like burnt cylinder oil. If you jack up the front you can get dang near 6 quarts out. This helps shifting and trans life.

 

Check your fan clutch as previously stated.

 

Check for codes, you may consider checking the CAT as well. That would cause power loss.

 

Change your fuel filter ASAP. I see tons of people on here with shifting issues and low power and it's just the fuel filter. Mine caused a shudder at cruising speed. Change your air filter when you do the fuel.

 

Report back with your findings. Good luck.

[cham]

Wow thank you guys for all of this information. I'm sure to try and do most of this but I now have a huge list of things to check. As for the codes, how would I go about checking them myself, or should I take it to a mechanic for that step? There seems to be no visible indicator lights on the dashboard but I'm guessing that doesn't mean there are still error codes. Now in regard with the fan clutch, I tried spinning it with my hand while the engine was cold and it has 7 blades and I observed that with a decent amount of force applied to spinning it, it only moved 1/7th a rotation. I'm not sure if this qualifies as a bad fan clutch because you said it should have some resistance but shouldn't be seized. My last question is does this pathfinder have 2 banks of catalytic converters since it is a 6 cylinder?

[LittleFR]

Your fan clutch has got to be bad. I just went out and tapped my fan with the engine cold and it spun like another half inch on its own and spins free either direction. Also I have 2 cats directly after manifolds and then an O2 sensor and 2 more cats. So 2 per bank.

 

Autozone or advance will scan codes for free. Most shops will but not all and the dealer will want like $40.

 

The CATs will be a huge PITA so I would do that as last resort, if it's burning oil that's probably your culprit, if it's leaking oil it's probably not.

 

First if would code scan (free) fix fan clutch because you know it's bad ($60)

then fuel filter ($12) and finally trans drain fill (6 qrts Nissan Transmatic D at dealer $45) if it still had troubles I would look into MAF (I'll give you a Maxima one with free shipping) but u have to do a MAF relearn.

[cham]

I have no check engine light on though and I believe that advanced auto parts or autozone will not want to do it unless a sensor actually set of a light. I do remember a while back when I was getting a check engine light serviced, after they said they fixed the problem, once it was handed back to me the light was still on so I had to take it back for them to shut it off. Could this mean they hadn't fixed the actual problem that made the sensor throw that light?

[jyeager]

If you do not have a check engine light on, there are no codes. So you are fine there. But if it's ever on, take it to the autoparts store and they will read it for free.

 

Since you are planning to replace the fan clutch anyway, start by removing the fan and starting it and taking it for a spin. You will immediately know whether your roar is caused by the fan. But the fan, when the clutch locks up, is known to make a very noticeable roar.

 

It sounds to me, from your description, that the oil leaking isn't enough to explain the loss of oil. So I think you are consuming oil. There are a couple of possibilities there. 1 is that you have one or more bad rings and are losing oil past the rings. You will be able to see this by doing a cylinder compression test. That needs to be done by someone who is at least an average shade-tree mechanic. You might be able to pay a friend a reasonable amount to do that.

Another possibility is bad valve seals, so oil is seeping from the top of the engine, down the valve stems in to the intake/exhaust. That is seen as a bunch of blue smoke when you first start your engine.

A third one is that the PVC system is not working right and oil is being sucked in to the intake and consumed. That would also be blue smoke, but not as obvious and not in a big blast at startup. It's usually easier to smell it. (if you know what burned oil smells like)

Also, if the PCV valve isn't working at all, crankcase pressure can build up to the point that it forces pressure (with oil) past the rings and it gets burned...even when nothing is wrong with the rings, or the engine otherwise.

 

All of these oil consumption issues will result in a buildup of black soot on the side of your truck in the vicinity of your exhaust pipe. Do you notice anything like that?

 

[cham]

Should the spot be on the back of my truck or on the sides of my exhaust pipe? Also I just figured out that my fan runs 100% of the time. From the moment I start the car up it runs until I turn it off. It still gets faster when I accelerate which I think it's supposed to do but it never stops spinning.

Edited November 27, 2016 by cham

[jyeager]

Should the spot be on the back of my truck or on the sides of my exhaust pipe? Also I just figured out that my fan runs 100% of the time. From the moment I start the car up it runs until I turn it off. It still gets faster when I accelerate which I think it's supposed to do but it never stops spinning.

 

It would be around your tailpipe. Assuming it exits behind your right rear tire, then the lower part of that entire fender panel to the back bumper. But also, if it's bad, the junk will be sucked in to your slip-stream and swirl around onto your entire tailgate.

 

The fan will always spin somewhat do to the natural drag of the viscous coupler. That doesn't mean anything. If you put a rolled up magazine against a fan blade and held it there, if the truck were then started, would you be able to keep it from spinning?

(asking you to guess, not try it. It would be dangerous if you screwed up and had your hand pulled in there). But in theory, if you did that experiment with a good fan clutch...and the engine were cold...you should be able to hold the fan.

[Citron]

That does seem like a lot of oil. If you are not leaking that much, then you must be burning it. When you start it cold, does blue smoke come out of the exhaust? Check the coolant and see if there is an oily film in it.

 

Also, for the rough shifts, change the tranny fluid and tranny filter. This will require dropping the pan, and can get messy, but is pretty easy. The torque converter should have a drain plug. This will get another 4 to 6 quarts out. That is the best way to get the most fluid out of the tranny.

Edited December 4, 2016 by Citron

[cham]

Okay at this point I have changed out the air intake filter and fuel filter. I've seen very miniscule improvements in power but not enough to indicate them being the main culprits to acceleration loss. The next step I feel is to change the transmission fluid and filter but don't have all the essential tools. Is a torque wrench a necessity in order to get the exact amount of ft-Ibs of torque for the gasket? Also what is the torque converter and where is it located? I know the more fluid you take out the better because it's being replaced with new fluid but is that necessarily that needed or is it something I should definitely do to get an accurate indication if changing the transmission fluid will fix things. Also if I were to do this, in total how many quarts should I end up with?

[Citron]

Scratch what I said. I am not familiar with your pathfinder and since writing the above post I have learned that auto pathfinders have a drain plug on the tranny pan, so no need to drop the pan unless you are also changing the filter. The torque converter also does not have a drain plug on these, so a flush is the only way to get the fluid out of the torque converter.

 

Torque wrench is not needed. Follow an alternating pattern on the bolts.

[cham]

I will definitely be dropping the pan in order to change the filter and examine the old one. My transmission fluid though seems cherry red like I had stated earlier on in this thread but it seems like the overall consensus is to still do the fluid change. Just out of curiosity why is that? Also something I feel is worth noting is that on my transmission oil dipstick, no matter how many times I check, I can't get an accurate reading. It just seems like the fluid covers all over the end of the dipstick. Could it possibly be that there is too much?

[cham]

I noticed yesterday that my transmission fluid dipstick almost seems like it twists when going back in the tube so that's most likely why I'm not getting an accurate level reading. How am I supposed to do a fluid pan drop if I won't be able to read how much I put back in? Should I just take it to a mechanic at this point to get the transmission checked out? Also how can I fix the transmission tube twisting problem?

[Citron]

Twist shouldn't be an issue. You are checking the fluid in park with the engine running right?

 

The owners manual should have capacity specs. If not, download the service manual and that will tell you.

[cham]

Recently my Service Engine Soon light came on. I took it to Advanced Auto Parts and they said the code reader was telling them the 2nd O2 sensor was faulty, the post catalytic converter one. I'll be getting it replaced soon by a mechanic but my question is, could this be a symptom of some other issue going on? Or is that itself the cause of some of my problems? One of the workers also told me I most likely had an aftermarket fan so that's why it's so loud.

[McFalconPunch]

9 times out of 10 its never the sensor, but the cat clogging up. By the sounds of your symptoms its starting to make sense what is going on.

Edited December 27, 2016 by McFalconPunch

[cham]

Oh so are you saying the cats are most likely clogging up, and the sensor became faulty as a result of that?

[McFalconPunch]

The sensor is still good, the code was probably for a P0420 or P0430, which are catalyst system below threshold, meaning they are not operating within tolerances. Do you have the code that popped up?

[cham]

He said it was like a high voltage or low voltage reading, I can't remember which meant the sensor was basically failing. I don't know if that helps.

[cham]

He said it was like a high voltage or low voltage reading, I can't remember which meant the sensor was basically failing. I don't know if that helps.

[McFalconPunch]

Well in either case, the rear sensor being bad doesn't affect driveability. Its there to let you know your catalytic converter is failing. If you can, go to AutoZone, they will give you a print out with the specific code. Or you can buy a $12 OBD2 Bluetooth adapter then spend $5 on an app called torque that will read info from various sensors throughout the vehicle.

[Citron]

Codes just point you in the right direction, but they do not take the place of proper diagnoses. If the code says O2 sensor, that is where the troubleshooting begins. You can't verify until you check the sensor to make sure it is functioning. Usually voltage, signal, ohms, and ground. Depending on what you find, then replace the sensor or continue troubleshooting.

 

Doing it properly will prevent changing unnecessary components and save frustration and money.

[LittleFR]

I don't know you or where you are or how much money you have or if your descriptions are accurate. Man it's tough on the Internet.

 

I would replace PCV and O2 sensors. And MAF. You did fuel filter and air filter. Your running 5-30 or 10-30 oil.

 

I'd use injector cleaner and run 93 and go from there.

Edited December 28, 2016 by LittleFR

[cham]

I see, hopefully things start to piece together and make sense at some point in the near future. Dropped my car off at a shop today to get the sensor looked at so I will report back the findings when I obtain that knowldege. I hope this faulty sensor doesn't mean my cat is failing! If so I'll be broke for a while. Realized the whole underside of my engine is covered in a thin layer of oil the other day so that's nice. Can't wait to get past this stage of fixing up and on to better things for the pathy!