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Sedans Nissan Altima Nissan Altima Engine Failures
495 messages, Last post on Nov 06, 2009 at 9:53 AM
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Replying to: electricdesign (Jul 27, 2008 6:08 pm) I thank God I discovered this site now I know much better, though ignorance is bliss.Can the scanners discover reason for low MPG? I am presently getting 18-22.3 in city and 26-31 in free way depending on driving conditions.I have read reviews of people getting 26/35-40 city/freeway and I get jealous especially with Camry and Honda.What am I doing wrong or is it the car? Chuma, Nigeria.
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Replying to: ndiboy (Jul 27, 2008 11:41 pm) Some of the top ones are: Autoxray Autotap Autoenginuity Mine is a 2001 model by Autoxray, it was $200 then. They now run about $200 and up. They have handheld models, and also have ones that plug into a laptop computer to give all types of fancy displays. Research them on the net , and you will find out all about them. Also Goggle "OBD II trouble codes" and you will find out all about the trouble codes (Diagnostic Trouble Codes) and how to read and interpret them. The codes do not tell you what part is bad or what part to replace, they point you in the right direction in your search for the problem. About your gas mileage, that is a matter of keeping the engine in good tune, to be sure all cylinders are firing properly, to be sure the transmision shifts properly, The transmission torque converter should lock up at cruising speeds, and driving habits play a big part, easy on the gas, keep rpms low when accelerating, and easy on the brakes. If you apply the brakes hard or stop fast, that is moving energy that is lost or wasted (lost gas mileage). Good Luck, E.D. ISF |
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ED, Seems like your the one to ask around here so here goes: I have a 2.5S with ~90000 miles on it. It burns 1 quart of oil every 50 miles. It doesn't appear that any coolant is getting inside the cylinders and the coolant level stays the same. I took out the spark plugs and in cylinders 2,3,4 you can see deposits and oil on top of the piston. The spark plugs look bad but nothing excessively bad. The car runs perfectly fine and there doesn't seem to be a loss of power. There is blue-ish smoke coming from exhaust as well. The problem started on the trip from FL to MD when the car was heavily loaded. Needless to say, I had to put in about 20+ quarts of oil just to get the thing home (it made it and still runs ok). I have had cylinder misfires. The oil looks really black (and not milky). I did a compression test and all four cylinders read in the 160-165 psi range. I was thinking scored walls but compression seems ok to me (atleast not bad enough that it burns 1 qt every 50 miles) and the car runs fine with no loss of power. Next, I was hoping it was only a head gasket but no coolant is getting in the engine (not sure if it is possible for a blown head gasket to leak just oil into the cylinders). So now I'm hoping for bad valves (but seems weird that 3 cylinders would go at one time). I've heard things about the pcv valve going bad but could this be a cause as well? Anyway, I was looking for your thoughts. If it is the valves, can they be replaced without having to take off the timing chain and cylinder head? Thanks for your help! Ben
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Replying to: bcole05 (Jul 29, 2008 9:58 am) First, I would check the PCV valve and hose, as a bad PCV can suck oil out of the engine crankcase and into the cylinders. You can temporarily disconnect the PCV and plug the openings and see if that makes any difference after 50 to 100 miles. Also, when the PCV is diconnected, see if you get much smoke (blowby gas) coming out of the hose that connects the PCV to the valve cover. You said the oil was very dark, how long does it take to get dark after an oil change? How often do you change your oil? You may need to change your oil more often, but I guess by adding so much oil, it's like a constant oil change. Second, the oil can get into the cylinders past worn oil control rings, those are the lower rings on the piston, each piston has 3 rings, from top to bottom, an upper compression ring, a lower compression ring, and an oil control ring. If the oil control rings do not work properly because they get broken, weak or damaged, they will allow oil to leak up past the piston into the combustion chamber and burn with the gas on top of the piston. Since your compression readings seem fairly ok, the walls are likely not scored. Replacing rings ia a major overhaul, having to remove the engine, very costly. Third, another thing that can cause high oil consumption is oil leaking past the valve guides, but as much oil as you have to add, it would have to be more than just the valve guides. If you need valve work, the entire head has to be removed and the head rebuilt at a machine shop. Have the engine and head checked by a competent machine shop. If you search these messeges you will find that I have went over all of that before and I have posted links to photos of the complete teardown and rebuild of the engine head removal, and head replacement, with links to many photos of it all. Forth, another thing that could cause this issue is that the "Power Valve Screws" have a nasty habit of coming loose on these cars and they get sucked into the intake of the engine, and can cause severe damage to the engine, if they happen to take a bad "bounce" before they finally find their way out the exhaust. They can even cause a cracked piston, head or valve. See previous messages about this issue, or Google it. Have you had any problems with the catalytic converters yet? Since you are burning oil, that oil goes through the cats and will cause them to fail eventually. I would start first with the simplest thing to check, the PCV valve and hose. Good Luck, E.D. ISF
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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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