[TJQMaster]

I have an 06 Nissan X. I (We) have been ttrying to identify the culprit of a OIL PRESSURE (<---correction) problem. The truck starts just fine and runs fine while parked. As soon as you increase the rpms while parked, the engine goes into this intermittent loss of oil pressure. It loses compression for 1-2 seconds, then comes back for another 1-2 seconds.

Its NOT:
Oil Pump
Oil sensor switch
Timing Chain
Timing chain tensioners

Any Ideas?

 

[Undrstm8ed]

Only way a cylinder Should lose compression is faulty rings, Perhaps you have a piston which has incorrectly clocked rings. Valve seals or bad valve lashing, OR there is a crack somewhere.

If you performed a leak down test yet? How are you measuring compression with the engine running?

 

[kms1990]

Only way a cylinder Should lose compression is faulty rings, Perhaps you have a piston which has incorrectly clocked rings. Valve seals or bad valve lashing, OR there is a crack somewhere.

If you performed a leak down test yet? How are you measuring compression with the engine running?

this^

 

[TJQMaster]

When idling, it doesn't lose compression. Only when under throttle either in park or driving.

The engine was rebuilt recently >5000 miles.

Hard to believe those new rings have gone bad after such a short time

 

[Undrstm8ed]

When idling, it doesn't lose compression. Only when under throttle either in park or driving.

The engine was rebuilt recently >5000 miles.

Hard to believe those new rings have gone bad after such a short time

So let me clarify your comments so we all get on the same page here.

When idling its fine as far as compression goes, but when put into gear and or i'll assume any throttle is given, it does what? Falls on its face? stalls? bucks? backfires? HOW do you know its losing compression is what I am getting at??

Who rebuilt the engine? Did they build from scratch (by scratch meaning Pulled all internals, replacing with new - bearings - rings - pistons - block hone - etc.. Zero miles technically) or just damaged or broken components? What was wrong that warranted "rebuilding"?

When you got the truck back. What instructions did they give you? Did you moderately break back in the engine? Did they use a SAE30 weight oil and in 500 miles do an oil change? Then run another 500 miles with reg conventional oil, change oil again. Run another 1000-1500 miles with conventional oil, then swap out to Synthetic oil finally?

I mean it IS entirely possible the builder incorrectly or inaccurately clocked the rings on the pistons but... I'm really curious about the aforementioned questions in as much detail as possible.

 

[TJQMaster]

So let me clarify your comments so we all get on the same page here.

When idling its fine as far as compression goes, but when put into gear and or i'll assume any throttle is given, it does what? Falls on its face? stalls? bucks? backfires? HOW do you know its losing compression is what I am getting at??

acts like it does when you remove the oil cap. bogs down I guess.

Who rebuilt the engine? Did they build from scratch (by scratch meaning Pulled all internals, replacing with new - bearings - rings - pistons - block hone - etc.. Zero miles technically) or just damaged or broken components? What was wrong that warranted "rebuilding"?

rebuilt engine after preventive oil pump/water pump maintenance didnt replace a small internal ball valve that controlled oil flow caused engine to seize. Rebuilt replacing pistons, rings, etc...with a kit similar to this...

When you got the truck back. What instructions did they give you? Did you moderately break back in the engine? Did they use a SAE30 weight oil and in 500 miles do an oil change? Then run another 500 miles with reg conventional oil, change oil again. Run another 1000-1500 miles with conventional oil, then swap out to Synthetic oil finally?

yes, and it ran fine for about six months before suffering SMOD

I mean it IS entirely possible the builder incorrectly or inaccurately clocked the rings on the pistons but... I'm really curious about the aforementioned questions in as much detail as possible.

ran fine for about six months before suffering SMOD

 

[kms1990]

acts like it does when you remove the oil cap. bogs down I guess.



rebuilt engine after preventive oil pump/water pump maintenance didnt replace a small internal ball valve that controlled oil flow caused engine to seize. Rebuilt replacing pistons, rings, etc...with a kit similar to this...

yes, and it ran fine for about six months before suffering SMOD



ran fine for about six months before suffering SMOD

SMOD should make the tranny have issues not engine

 

[TJQMaster]

SMOD should make the tranny have issues not engine

yes, I just mentioned it as a part of a sequence of events.


ALSO....my mechanic and I discussed the possibility of it being a loss of compression due to incorrectly installed piston rings. If it were the rings, the engine would produce a lot of smoke.

we are also considering the crankshaft bearings!?!?!?

 

[kms1990]

so you got the smod, what did you do to remedy? did you catch it before it went to far? if not you very well may have a tranny issue that seems like an engine issue. as you say it idles fine but when you dhhift into gear (meaning the transmission is now active) it loses compression, and what exactlya re you feeling? is it stumbling? misfiring? wont go? what exactly leads you to this conclusion its engine related. the smod has a high chance of taking out the tranny as coolant a nd tranny fluid dont mix and coolant will ruin a tranny fast.

 

[TJQMaster]

forget the tranny. Its not the tranny. I can tell the difference.

Its a compression problem.

 

[kms1990]

forget the tranny. Its not the tranny. I can tell the difference.

Its a compression problem.

Yeah, i get too used to people not knowing the difference just its broke! Lol

 

[TJQMaster]

any ideas on the theory it may be the crankshaft bearings?

 

[kms1990]

any ideas on the theory it may be the crankshaft bearings?

not too familiar with symptoms of a worn crankshaft bearing but it could be a possibility. i try not to give advise on subjects i'm not that familiar with

 

[TJQMaster]

Appreciated

 

[TJQMaster]

I just realized something. Ive been using the terms "compression" and "oil pressure" interchangably.

WRONG!!!

I meant OIL PRESSURE

 

[kms1990]

yes, oil pressure drops can come from scored (bad) engine bearings, clogged oil pump, or pick up, failing pump low oil wrong weight oil and a few other things. it is normal for oil pressure to fluctuate with engine load and engine speed

 

[TJQMaster]

just spoke to my 3rd Mechanic. One after the guy who COULDNT find the problem. Apparently ive got a broken piston rod. FML!

 

[kms1990]

but it starts and idles? that doesnt add up.

 

[TJQMaster]

to me more specific. I have some sort of failure where the rod bearings were damaged and got a lot of scoring