Hi, I'm new here...
My 01 "Q" is making fairly loud piston slap noise when the engine is cold. It goes away after several minutes, but is quite severe when cold.
Has anyone else with the 3.5 engine experienced this? The dealer that sold it to me says this is "normal" for these engines. I know the older Pathy's had some piston noise, but this is the first I've heard of it on the 3.5 l.
Do I need a new engine? Only 140,000kms.
The other concern is this: I think the knock sensor detects this piston knock, and trys to retard the timing to compensate. This must effect gas mileage also...?
I welcome comments, advice.
i've always associated piston slap w/ the rings being worn out, the engine will burn oil because it will blow by the rings. are you sure its not a rod knock starting or a main. what weight oil are you using, it might be thick when it is cold. i had a knock noise on my 95 windstar which turned out to be from a failing oil pump, it would knock when cold then go away when warm, inspected the bottom end and replace all the bearings (mains and rods) because a main was starting to fail because of it. see if you can find a scan tool that reads the sensors while the eng is running and check the oil pressure, just to be sure.
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Dave
96 4WD XE Reg. Cab ka24e
Calmini 3" SL, Steering, Lock-rite rear, LSD front
i've always associated piston slap w/ the rings being worn out, the engine will burn oil because it will blow by the rings. are you sure its not a rod knock starting or a main. what weight oil are you using, it might be thick when it is cold. i had a knock noise on my 95 windstar which turned out to be from a failing oil pump, it would knock when cold then go away when warm, inspected the bottom end and replace all the bearings (mains and rods) because a main was starting to fail because of it. see if you can find a scan tool that reads the sensors while the eng is running and check the oil pressure, just to be sure.
search for valve noise at start up and tappet noise wen cold in the forum... that is infact common on nissans piston slap is NOT common. My guess is your hearing valve noise at cold start up.
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Poor planning on your part does not constitute an emergency on my part........
search for valve noise at start up and tappet noise wen cold in the forum... that is infact common on nissans piston slap is NOT common. My guess is your hearing valve noise at cold start up.
I second that.
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Life is too short to take it too seriously
My QR25DE had some piston slap when brand new. I can't say how common it is in other Nissans ... but it is more common among all engines these days. Why? Because it is often caused by shorter piston skirts used more and more by engine builders as a way of cutting down on reciprocating weight which adds horsepower and fuel economy ... and reduces stress at higher RPMs.
As a piston skirt (side) wears, the piston tends to rock and "slap" against the cylinder wall as it goes up and down making a deep sound often like a bad rod knock. This is especially acute in cold weather because the aluminum piston is shrunken. As the engine warms up, the piston expands to better fill the cylinder and the noise gradually decreases over the first several minutes.
Piston slap seems to be especially bad with Mobil 1 ... probably because it is thinner than most other oils at the same temp.
Oils high in moly (molybdenum) such as Red Line can cut back on piston slap noise as can thicker oils ... but don't go too thick in the cold as increased wear during cold starts will likely be the result.
However piston slap, despite being annoying, is usually benign.
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--- Bror Jace
Last edited by Bror Jace : Dec 14th, 2005 at 10:59 PM.
It is definitely piston slap, I've heard it many times on other vehicles, also the dealer agreed that is what it is. I've tried Mobil 1, and as mentioned in previous post it was actually a tad worse. I am presently using 10-30 oil.
I guess my concern is the knock sensor will "hear" the knocking from the pistons, and retard the timing to compensate, thereby reducing performance and economy. If I understand correctly, the ecm remembers the knock conditions at startup, and doesn't change timing settings again unless you restart the engine (after warm-up).?
I'm not experiencing any oil consumption issues. Just noisy. It leaves me feeling this is a poorly designed, and likely short-lived engine. I sort of expect piston noise from a chev or jeep, but not an Infiniti!
It is definitely piston slap, I've heard it many times on other vehicles, also the dealer agreed that is what it is. I've tried Mobil 1, and as mentioned in previous post it was actually a tad worse. I am presently using 10-30 oil.
I guess my concern is the knock sensor will "hear" the knocking from the pistons, and retard the timing to compensate, thereby reducing performance and economy. If I understand correctly, the ecm remembers the knock conditions at startup, and doesn't change timing settings again unless you restart the engine (after warm-up).?
I'm not experiencing any oil consumption issues. Just noisy. It leaves me feeling this is a poorly designed, and likely short-lived engine. I sort of expect piston noise from a chev or jeep, but not an Infiniti!
Animal correct me if im wrong but pison skirts are never meant to touch the cyliders and if they do then you have a very serious problem. Infact they are arent ment to wear at all. As for mobil 1 its pretty much all i use and i have 200k + on my 97 and never once had a piston slap. If your making the statement that the skirt needs to be lubricated to prevent wear then Im just shocked by the concept your proposing.....
Pistons should never slap.
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Poor planning on your part does not constitute an emergency on my part........
Animal correct me if im wrong but pison skirts are never meant to touch the cyliders and if they do then you have a very serious problem. Infact they are arent ment to wear at all. As for mobil 1 its pretty much all i use and i have 200k + on my 97 and never once had a piston slap. If your making the statement that the skirt needs to be lubricated to prevent wear then Im just shocked by the concept your proposing.....
Pistons should never slap.
I concur. Infact no part of the piston should touch anything at anytime. except for connecting rod and rings (normally)
Now I have a question in regards to this... (i'm in noway even a backyard mechanic), I barely feel comfortable filling the air on my tires (LOL). My 01 Pathy (69K Miles). Makes what sounds like a whinny noise for the first minute to 2 minutes of driving under cold conditions. I'm thinking is just normal since it goes away and does not come back. If the engine is warm it'll never do it.
rmd0311, it sounds like that's a belt or a pulley ... I'm guessing a belt. You could swap out your belts (are they about due anyway?) or try belt dressing ... a spray that can be messy if not applied carefully.
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