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Discussion Starter · #1 ·
Hello guys, first time poster but I have frequented this site for a lot of information over the years.

My wife's 02' Xterra has developed an awful knock (VG33E, no SC). It began as the engine running rough at idle - she said the fuel had gotten the lowest it had ever so I though maybe it was just junk in the tank had clogged up a filter or something. The next day the rough running slowly turned into a sharp knock. It sounds almost exactly as in this video: https://www.youtube.com/watch?v=48KGzC9RS5U only it doesn't come and go like it does in that video.
If I tap the gas the sound disappears for a second and gets really really loud as the RPMs drop. Also I might add that the valve seals need to be changed so it does go through some oil, my wife didn't check and it was pretty low - not even on the stick but the low light never came on.

I have so far: pulled codes (P0304). Checked spark on cylinder #4 . Pulled spark plug on #4 , bore scoped #4 (through plug hole # intake to see valve - seemed to me like there is more oil than normal in the cylinder), replaced all lifters with new ones. Checked and adjusted timing (no effect), pulled a plug wire from the cap one at a time to see if it would make any difference (no difference), cranked the engine while the VC is off to view the valves - everything looked fine.

A new timing kit, water pump, bearings etc were installed probably 900 miles ago. The engine was perfect up until now. The knock sounds like it is on the top end but its always hard to tell. A thought was maybe somehow the camshaft jumped a tooth on the belt but then the issue would have happened suddenly and not slowly. Could a rod cap have worked loose?

Any help is much appreciated guys.

Thanks,
Dan B.
 

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Definitely sounds like lifters, valves, or poor oil flow to me...I would bet your oil pump isn't performing quite high enough, or you have a clog somewhere in your oil passages

Darin
01 Xterra SE 4x4
COMING SOON:
Intake mod, timing belt, hoses, belts
Wish list:
PML, EFan conversion, shocks, 32" tires, and eventually UCA'S
 

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Discussion Starter · #4 · (Edited)
I resolved this by purchasing a used block, used crank, used heads, used rods and a new engine kit.

Your problem is not the same as mine. I did a compression test and it turned out I had 0 on cylinder 4, I pulled the head and found the piston to be cracked and the wrist pin pushed against the cylinder wall causing a deep score. Somehow I missed this score when I was using the bore scope. Using the new used parts listed above, I rebuilt everything again- now I have a nice healthy running engine with no noise, and as an added bonus I no longer have to keep on filling up my coolant reservoir because of a mystery coolant leak (turned out my passenger side head was cracked - hence the reason for new heads).

If yours is making noise after a belt change then start there. Did you do the work? If so, did you make absolute sure you were at TDC, that the cam sprockets were close* to their mark and did you count the teeth on the belt between the two marks along with the teeth on the belt between the mark on the passenger side sprocket and crank mark?

Edit: I forgot to add my reason for the * above:

*-I say close because it seems, at least on my engine(s) that I rebuilt, the notch in the metal doesn't line up exactly with the dots on the camshaft sprockets but they are close and as long as you have 40/43 teeth per the shop manual you'll be fine. Its also important to make sure you're at TDC - even though the book says there is a dot to line up with the crank sprocket, I've never seen this alleged dot. If you miss a tooth, you will have valve noise as your timing is off. If you miss more than a tooth or you're not at TDC, these are interference engines so it could be a valve hitting a piston. If you have any kind of high mileage, you'd benefit from spending the $50 to get new lifters too while your at it. At 119K, half my original lifters were shot.
 

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Thanks Dn010 for the reply,
originally I had changed the timing belt and crankseal with a buddy, it was our first time working on an Xterra and we screwed something up along the way. After taking it to a local mechanic, they took it apart and couldn't figure out the knocking either.

They said in order to fix the issue, they would have to take a apart the head and it would cost me about the same to change a new motor. So I had to fork up $2500 for a replacement JDM motor with 50K. It runs smooth and quiet now.

To those who have never changed timing belts or crankseal, don't do it unless you have experience and the proper tools, because you can end-up damaging the entire engine. Happy riding!
 
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