[angelman]

I believe I have reached the end of the road with my pathfinder. I have tried everything and its still not working properly.
Brief history:
bought brand new in 2001, top of the range model with all extras.
Always been serviced by nissan dealer, kept in perfect condition, all oil changes etc. etc.
Then last year I left the car for a week whilst on vacation. My sister moved the car out of the drive way and suddenly all the oil dropped out of the engine.
By this time the car is out of warranty of course and I have an excellent mechanic. He pointed out that many things that should have been changed by the dealer over they years in fact hadn't. Anyway after a week or so of diagnosis he discovered that one of the cylinders and pistons was totally melted, just one piston mind.
I decided that since the car was perfect in all other ways to have the engine rebuilt rather than buy a new equivalent car which would probably have cost around 40K.
After a huge struggle we found new pistons (this engine used a very rare size - one of 3 used for that year). Everything looked good, new o2 sensors were put in and the computer recalibrated.
After a week the check engine light came on and the engine was knocking when driving up hills.
After more diagnosis we discovered the computer was pumping in too much fuel. It was complaingin about the sensors. These were changed once more. Everything else was checked too, vaccuum leaks etc.
Still there was a problem. We bought a new computer, and the problem is still there.
We have replaced almost all the engine components and sensors now!
I really dont want to just junk the car but its still knocking and most likely will end up failing fairly soon.
The knocking occurs at almost precisely 2300 revs. I suspect this is when the variable intake manifold kicks in. It is getting worse and the car is very rough when cold. It often stalls if you try and drive it straight off in the morning.
My mechanic has been through everything with the dealership and they have all given up on it.
Is there anything anyone can think of before I am forced to junk this perfectly good (except for engine) car. I feel sure its something small that we have overlooked somewhere.
We even upgraded the firmware in the computer to see if that helped. Maybe there was just an design fault in the car since it was made. It was one of the very first to be shipped to California at the time and I think the engine was new for the year.
Help! I dont want to buy a new car

Many thanks

 

[dvdswanson]

it seems that the veh. was perfect before the trip, lost the oil and drove it damaging the engine, the engine heated up causing the cylinder to melt. you should have repl the engine at that point (IMO). as well as the sensors connected to the engine because they as well were overheated. unfortunately no codes are being set to tell you which one(s) are acting up. if you love the veh. start replacing sensors but it will be pricy otherwise sell the veh. sorry cant be more help.

 

[angelman]

I thought the same about the trip but once the knocking had been identified I remember hearing a similar soudn for some time before the trip. I think that driving it without the oil certainly caused the piston to fail. There is a question as to why the oil was lost but at this time is not relevant. Once the cylinder melted we did replace/rebuild the engine. Every part of the engine was replaced by a professional engine rebuilder. It took 3 months to track down the correct piston. There were only two in the country and every nissan dealership had orders in on them. We eventually found enough to complete the rebuild. As I said we also replaced most of the sensors o2 sensors etc. some more than twice. The code that the check engine light gives seems to be a little odd since it refers to something that we have both replaced and checked (I think its to do with an o2 sensor).

 

[dvdswanson]

can you tell where the knocking is coming from? i.e. left or right side top end or bottom end, frt or rear of engine? it is possible (not likely, but possible) the tech got a tooth off on one of the cam gears or crank grear. causing the knock. is the knock a ping sound? possible the knock sensor. IDK just throwing thoughts out there.

 

[angelman]

It's a little hard to isolate exactly where the sound is from, but pretty sure its from the engine area. It only occurs when the engine is under pressure, ie. when accelerating up a hill. Actually it's getting worse now so it happens even when the engine isnt under a great load. Right when the rev counter hits around 2200rpm or so it starts, like chattering ticktickticktick sort of sound. The engine has veyr little power at this point. Going up a long slow hill for instance I can barely do 40mph without the sound occurring. Stepping on the gas makes it much worse (louder). My mechanic says its knocking/pinging/detonation. In his tests he found the computer was putting too much gas into the engine. The problem he could determine is what was causing the computer to do this. I was looking at another forum/thread which was talking about failed MAF sensors causing lost power etc. I am not sure if we replaced that or not. The computer check engine code was something quite strange. The mechanic could not even find it in the code book. The dealership garage would not say what it was either. Eventually we traced it on a forum to being a code for malfunctioning o2 sensor or something like that (which had checked and replaced)

 

[dvdswanson]

too much gas? check the coolant sensor.

 

[IanH]

Did you guys check the power valves and swirl valves in the intake for loose screws and butterflies ??
did you get the butterfly screws loctited ?
I read here that the butterfly gets jambed in the intake and vibrates like crazy at a fixed rpm.
Did you check your Oil before all this happened, these engines use Oil even when new not just the rev up 95 -96 's.
Why didn't you consider putting in a used engine. This would have been an ideal candidate. complete, no new sensors and pistons to find. Would have been better and cheaper.
Also what was replaced when the engine was re-built.
ie All pistons with a re-bore, crank re-grind, new Oil pump etc. ??

 

[IanH]

too much gas doesnt cause pinging, the reverse, too little gas causes pinging.

 

[knight_k1dz]

is your problem similar to mine??