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Sedans Nissan Altima Nissan Altima Engine Failures
497 messages, Last post on Nov 21, 2009 at 8:01 PM
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Replying to: electricdesign (Jul 29, 2008 5:18 pm) I checked all the spark plugs and they looked ok. Dirty but not excessively dirty. As for the oil, I change it religously every 3000-3500 miles. I have not done an oil change since the problem (figuring I was basically doing one all the time). Before the significant increase in oil consumption it didn't get black right away and the engine probably burned 1 qt every 1000-1500 miles. And then all of the sudden it shot up to 1 qt every 50 miles on the trip home. Now the oil is constantly dark even after adding more. When I pour in oil, there seems to be fumes coming out of the oil port in the valve cover. Not sure if this is because everything is hot, or if this is normal, or if it is exhaust fumes exiting from a busted valve that is being trapped in the valve cover. From my understanding of what you wrote, it is possible to have a bad oil control ring but still have decent compression. Is this correct and do the rings usually fail all at the same time or could just one fail? I have not had problems with the precat or cat yet. However there are codes that are stored and I will be borrowing a friends code reader tonight to see what they are. Since I had to add so much oil, I am already planning on having to replace the cat and the precat (but either hollowed out or with a header) assuming the engine can be fixed for a reasonable amount of money. I guess my plan of action now is to check the codes and see what they say first. I will try to replace the PCV valve and hope that fixes everything. Then I would like to take off the exhaust manifold/precat and see what the inside of that looks like. If theres nothing left, I would expect the problems to be much worse than feared. I was also going to take off the valve cover and look around, but will I really see anything from just doing this? Next, I was going to check out the intake manifold and see if all the butterfly screws are still there (I am assuming thats the same thing as the "power valve screws"). Do that seem like a reasonable path to take? One last question, is there any reason to take it to the dealership do you think? The car and exhaust components are out of warranty (~90000 miles) and since I have a code reader and already did the compression test, I don't want to pay for someone to tell me something I already know. I am figuring that since I don't have oil reciepts, a maintanence history through Nissan (I do everything myself), and the car is out of warranty, I will have no chance at getting Nissan to help fix/pay for anything. Thanks again, Ben
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Dear ED, Thanks for all the contribution so far, its been wonderful joining this forum.I have indeed learnt a lot from you guys. My exhaust pot has two outlets and I normally check the gas coming out of it.I noticed that the pipe to the right from the back blows out cold air while the one to the left blows out hot air.Is this normal? just a chance discovery by putting my hand there when i start it in the mornings. I also want to find out the meaning of PCV valve and hose and where they are situated in the engine.I am a doctor and the PCV I am used to is 'Packed Cell Volume'. Now I know better I am afraid to travel with this car, Ignorance they say is bliss, but knowledge is still supreme so I want to learn more and more. Thanks to electricdesign (trying to figure out the name or guy name). Thanks, Chuma. |
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Replying to: bcole05 (Jul 30, 2008 7:00 am) But first, do what I asked in the previous message, check the engine crankcase for combustion blow by gases. Leave the oil filler cap ON the valve cover, pull the hose off the PCV valve. The other end of that hose should be connected to the valve cover. Start and run the engine and see if smoke or gas blows out the hose and if any, how much. A good engine will not blow any smoke, a bad engine with blow by will blow smoke. The gas or smoke is combustion gas that leaks past the rings into the cylinders. If no blow by, you still have a problem yet, since you know that the engine is consuming oil and that smoke comes out the exhaust. It is possible that oil could be leaking past the valves, but it is hard to believe that that much oil could leak past them. To look at the Pre Cat (first cat), don't unbolt the exhaust manifold from the engine. Unbolt the exhaust pipe from the bottom of the exhaust manifold (two bolts with springs), under the car, and look up inside the exhaust manifold. You will be able to see the lower cat screen if it is there. If the cat has blow out clean, that is one less thing to worry about, except for where the stuff went down the pipe (usually clogs up the 2nd cat). Unbolt the exhaust pipe to check the 2nd cat. About the dealer, I don't think you will get any help there, unless you like to spend a lot of money. Good Luck, E.D. ISF
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Replying to: electricdesign (Jul 30, 2008 8:07 am) I have been looking at mine with my mechanic and wondering where to approach it from.He wants the approach you advised against so I need reasons to give him. thanks,remember question 301 please. Chuma.
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Replying to: electricdesign (Jul 30, 2008 8:07 am) So after all that, I decided to recheck the compression since nothing seems to be adding up to why its burning so much oil. Well low and behold the compression was 135-142 psi for all the cylinders. I don't know what I did differently the first time to get much higher readings. I haven't really driven the car since the last test. If anything, this time the engine was hotter so you would think higher compression numbers. So its looking much more like a new engine will be needed. And if this is the case I will probably be getting rid of the car unfortunately. I love the car when the engine is working. I think getting a new engine or having the dealer replace it is just not worth the time/money, especially when the cars only worth ~$5700. Thanks for your help ED! Ben
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Replying to: ndiboy (Jul 30, 2008 11:53 am) About the exhaust at the back of the car, you have a single exhaust with a single muffler with a single tailpipe that splits into two tailpipe tips. As long as you have good exhaust gas flow out of either pipe at the back of the car, you are ok. This is only for single exhaust cars. Cars that have dual exhaust, such as the V6, must have good exhaust gas flow out of BOTH left and right tailpipes. About the "PCV I am used to is 'Packed Cell Volume'." PCV Referring to automotive is Postive Crankcase Ventilation. "electricdesign (trying to figure out the name or guy name)." That is simply my job as an electrical designer, hence the abbreviation E.D. Good Luck, E.D.
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Replying to: bcole05 (Jul 31, 2008 3:34 am) Check you compression tester, it's always best to use quality reliable equipment, because wrongs readings can throw you way off track. I use a qualitiy screw in Pearless compression tester, with a heavy duty 2 foot flexible hose. "So its looking much more like a new engine will be needed." Unfortunately, I think you are about right, since the compressions are now reading low. That would give much stronger indication that oil is leaking up past the pistons and rings into the combustion chamber and burning with the oil. I would agree that a $5700 car is not worth a new engine, unless it is a restoration project or of great sentimental value. Good Luck, E.D. ISF |
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Replying to: electricdesign (Jul 31, 2008 5:09 am) Maybe I will use his tools and pit in the workshop and have a look for possible hollowing of the pre cat and have peace. The PCV's air flow is supposed to be clear and colourless I presume.The one in my Bluebird brings out dirty oily black gas but I cant seem to locate that of my Altima. Thanks, Chuma.
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Replying to: ndiboy (Jul 31, 2008 6:15 am) Since you may try to look into the exhaust manifold/pre cat yourself, look at what I wrote in messege #306: "The bottom bolts of the exhaust manifold, where the exhaust pipe connects, definitely do get rusty and stuck tight. That work is easy for me because I just use my acetylene torch to heat them red hot and they come right off." I would count on the bolts being rusty and tight, so try to be prepared for the worst. Exhaust components usually are rusty and stuck, so this should not be a problem if the mechanic is familiar with this type of work. I don't know if you have an acetylene torch or anything to get rusted tight nuts loose. If you get stuck, and can't get it off, then just let the mechanic have a crack at it, as he has to take that exhaust pipe loose anyway, before he can remove the exhaust manifold. See teardown photos DSC06886 through 06888. If you try to hollow out the pre cat, I would recommend that you first remove the oxygen sensors to avoid damaging them. You may likely need a special socket for this, if they are tight, and they usually are. The special socket has a slot up the side to allow the socket to slip over the wiring. See teardown photo #06892, this photo is on the upper O2 sensor for clarity of the photo, but you need to remove the lower O2 sensor also, as it is in the most danger of being damaged during the hollowing out process. The PCV valve is located bolted with 2 bolts to the Intake Plenium, on the end of the hose from the valve cover, see teardown photo # DSC06959. If you pull the hose off the PCV and start the engine, there should be only a small amount of gas, if any, coming out of the hose (coming out of the inside of the engine), and it should be colorless (we have color here, not colour). If dark or smokey, it indicates an engine problem, which is too much combustion gas in the crankcase, also called blow by. The cure for blow by is a new or rebuilt engine. Good Luck, E.D. ISF
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Replying to: ndiboy (Jul 31, 2008 6:15 am) Unscrew O2 sensors carefully, if they start to get tight when unscrewing them, spray some penetrating oil on the exposed threads and screw it back in a little and work the sensor back and forth a few times to work the oil into the threads. Apply oil as often as needed. It should loosen and eventually come out. Before putting a used or new O2 sensor back in, coat the threads with a small amount of Neverseize compound (available at auto parts stores). Put the Neverseize carefully only on the threads, do not contaminate the sensor with the compound. This will help in the future, in case you should have to remove it again. Good Luck, E.D. ISF |
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