95 Altima Engine problems

[albetime]

Hi All Newby here! Just bought a 95 Altima for my kid with problems. Here is the history on the car: 95 Altima, auto, 130K miles, looks like someone kept pouring oil on the valve cover and some in the engine. Engine doesnt make any knocks(ie: no bad rod bearings) so here are the problems.Scanned the codes and results are: 1) P0400/ EGR flow malfunction// 2) P0130/ O2 sensor Circuit bank 1 sensor 1// 3) P0325/ Knock sensor1 bank 1The car has a bad engine vibration around 1500 RPM and will smooth out to normal as i accelerate to 2000 or higher until it shifts and RPM drops. I suspect a faulty engine or trans mount but the front mount looks fairly new but still could be bad. The distributor cover has been rubbing the hood like the engine has been lifting up some from a mount. The vibration is transmitted thru the body and also makes the dash rattle/vibrate. I believe that the Knock sensor fault is caused by the excessive vibration! I believe there is only one knock sensor and that my code reader states bank1 one as a default?

The O2 sensor forward one has been replaced 2 times by the previous owners mechanic and that code never goes away after it was cleared. I am not sure why i dont get O2 sensor bank 2 fault maybe thats just my code reader? I cleared all codes prior to the ride home. 5 miles later the check engine light was on again. I believe that there is a 2nd O2 sensor prior to the converter?

The EGR flow fault? I checked the operation of the diaphragm for movement and it feels smooth and is not sticking. I read that there maybe a EGR gas temperature sensor but would that give me the same fault? If its not the same fault then maybe there is a restriction or clog in the piping with carbon?Well any help or advice will be appreciated!Thanks in advance

Update!!Vibration is caused by front mount completely deterioated.
Modified by albetime at 6:36 PM 4/9/2009

[3Q Jay]

good cars these are (when maintained--most can tolerate neglect for a while, but many are now showing the signs of owner disdain and neglect).

you already found one common problem area. there are 4 mounts total--tranverse also on transaxle side, and longitudinal front rear on the center subframe.

the ks is pretty common at this point, but also could be a sure sign of an overheat. radiators crack at the upper tank aft side near the hot hose.there is no bank 2 (I4, not V8) O2 sensor. might have a rear one, i'm not near either U13 at the moment.

EGR. welcome to the world of previous owner neglect. there are varying degrees of perfection. the sure way is to remove the egr and rooter out the intake passage, and the tube that wraps back to the exhaust manifold. look for some of my posts in this (u13) forum, i list the EGR gasket numbers, and also have some pics of full plenum removal which also show you the ks replacement.

[3Q Jay]

other things to watch for at this age:1. distributor (likely yours has already been replaced)2. ps suction hose. what's the big deal? leaks drip on the lower control arm and rot out the rear bushing.

[albetime]

Thank for the info! Worked on the car this weekend and found that the front and rear motor mounts were bad, after replacing them the vibration was gone. I also cleaned the throttle body which was carboned up and sticking, this helped with the irratic idle at times. Gave the engine a complete cleaning from the all the oil that had been leaking from the valve cover gasket which I also replaced. 2 of the 3 codes are gone now and only the O2 sensor code keeps comming back but I have not tried to troubleshoot that further. Previous owner said it was changed 2 times and the code keeps comming back? I looked into the distributor but didnt see any signs of oil so that was good. I am not very impressed with the mechanic they used since he wanted to disassemble the engine to find the vibration and also didnt tighten the upper rad hose so it started to leak.

Now another concern is that I hear a noise comming from the timing cover and I will try to put the sound into words but I know thats willl be difficult!Using a steathoscope, the sound seems to be comming from inside the timing cover. The noise sounds like a crackling sound, sort of like a bearing with a flat spot on it. Its not too loud but you can hear it and its not a constant rotational noise. Well my question would be what are the most common items that fail in the timing assembly? Idler bearing? I know that the guides will wear but I think that would be a slapping sound from the timing chain if the chain was worn? But that doesnt sound like this noise. Any help will be appreciated!!!! Thanks in advance

[Rev_D21]

For the noise coming from under the valve cover: Take off the valve cover. There is a timing chain guide at the top of the chain, looks like a flat piece of metal held by two bolts. Remove that guide and discard, it's known for making noise.

[albetime]

Thanks and I am familar with the chain guides but I didnt realize they were such a minor issue that they could be removed without any adverse affect if the chain gets too much slack in it? Is it standard practice just to remove them? I built many engines but never tried to just remove them because back in the day if a chain had so much slack that if the guide wasnt there it would actually eat into the timing cover. At least I can remove the top one without too much trouble just to see if the noise goes away and check the condition of it. Thanks for the info!