Lately i been hearing a knocking sound from my engine, i did a little research and pinned the sound to the middle cylinder in the front, if i disable the coil for the cylinder it knocks pretty loudly, all the others are quiet with this procedure, what are your opinions on this ? can it be a rod, wrist or main making the noise or could it be something in the valve train ?
Any suggestions are well appreciated . thanks.
2000 Maxima 3.0 engine.

 

Got a clip?

 

loose valve?????

 

lol
valve is never loose , it's actually always under tension as cam presses it down to open it and spring tension closes it as cam rotates it's lobe.
You might have piston slap or a worn rod bearing
Pull out your spark plug to see what it looks like and see if the porcelain is cracked or tip is damaged. TRy even replacing it.
it's something in the bottom end most likely since it gets louder when you disconnect the coil due to no ignition and pressure applied on piston travelling down.
Take a long screwdriver or stethoscope or even a rod and stick a piece of wood and touch the bottom of engine and then the top and put your ear to the other end carefully without touching anything like fan etc. and listen where noise is loudest.

 

so then, why the valve needs adjustment? Maybe I used the wrong word.

 

The Hondas (every 100K) and some Toyota Yaris (every 48K)need valve lash adjustments but not these ones. Those are different designs. These have caps made of different thicknesses and you could actually cause some noise if you mismatch cylinder Nr. when you do an engine rebuild and have the cams off as they are different thicknesses . Also like you said they are adjustable by removing the cap and adding shims underneath if noisy in theory but also not common on these motors.
ALso valve noise is more like a tick than a knock.

 

its not something i can take on my self if its a bearing.

 

well pull out the plug yourself and see what it looks like if you want pull off another cylinder one and compare them together.
Other than that you wanna diagnose it properly as it is something i think it is from what you described.
If it is a rod bearing or crank bearing it needs an engine tear down. So don't get scared as of yet, get it checked out.

 

i just recently installed new ngks about 4k miles ago, i checked it as you said and its fine.


i just want to cry now.its like having a child and being sick and not knowing how to help the pain.

 

no sound clip, its not real loud and if your just standing there you would not really notice it unless your listening for it, just a clunking sound

 

UOA (used oil analysis) time. Unless you want to tear down the engine for fun. Will probably take a little while for the results to get back though.

 

I had an issue with the engine knocking......i did one of two things.....octane booster and/or changed the oil

 

This is not a detonation knock, its more of a clunk at idle, you cant hear it once you come off idle. I always use 93 to 97 octane fuel, never less.

i just recenly switched to castrol syntec after using Mobile 1 and not liking the associated noise i had with mobile 1 , wich was valve train noise.

 

I will add a +1 to this. The valvetrain does not knock.

 

Sounds like you have a slack rod to me.

If it does turn out that your rotating assy. is messed up I would just recommend finding a low mile junkyard motor.

 

should i cry now or later ?

 

are you running on regular or premium? a friend of mine has an acura that's supposed to run on premium, he put regular in, and it started knocking....switched back to premium and its run fine since

 

always 93 or more, i never use lower.

 

Ok people here are obviously confusing knocking/pinging/detonation with a mechanical knocking noise. Big difference here guys.

 

can be a pistion slap

 

Spark knock vs rod knock.

 

You could always pull the oil pan and plasti-gauge the rod bearing. If your going to go that far you may as well just replace them. A set of rod bearings would probably cost you less than $50 and an afternoon to put them in (at most). It could fix your problem or it could just be a waste of time but I think its worth the risk before you go pulling a motor. If it gets worse as your motor warms up (oil viscosity thins out to normal) then its almost certainly rod knock. If it gets better as your engine warms up then I would lean towards piston slap but thats not likely unless some one has been in there before and missed the piston/bore tolerance by a bit.

 

a rod bearing usually sounds like a knocking noise, piston slap sounds like ticking noise.

 

yup its a steady knocking almost like grabbing a bar and tapping on the block.

 

And it is constant and RPM dependent right? If so, from what you have described so far sounds exactly like rod knock to me.

 

yeah, can only hear it at idle when its warm, first start cold is quiet till it warms up and expands abit.

None of the local auto part stores here have the rod bearing kits either........ it would not be to hard to replace, BUT i need the parts

 

Yikes, yea thats definitely rod knock. I had the same thing on my Volkswagen Golf 8v. Although mine did it really bad when cold and get better as the engine warmed up.

I don't think you will find it at a local auto parts store, but maybe try a block shop. When my friend had his Suzuki Samurai engine disassembled and re-machined at a blockshop they had the pistons, rod bearings, seals, everything.

Good luck!

 

BTW, I am kindof a maxima newbie, I just bought my car not too long ago (a 4th gen), and I am curious, I thought the VQ's and most Nissan engines for that matter were pretty damn solid. Are bottom end problems like rod knock and such common at all on our cars?

The only times I've seen it really is when a car is poorly maintained, has a manufacturing defect (thrust bearings on 99 Miata 1.8's were the wrong size from the factory and failed within 30K miles on those select cars. <-- an example of it), or just has crazy forced induction or something.

 

so sad, i want to do the work myself to save money, i just priced a new engine and its almost 4K........ all i paid for the car was 7K. a new one is not the answer, car is perfect otherwise.

 

What are you pricing, brand new from Nissan? Get a junkyard motor, throw it in, call it a day.

 

Or what about pulling yours and doing a complete rebuild? Might be cheaper even than a junkyard motor and plus then you have the piece of mind knowing you are running on an absolutely good as new engine that you know you assembled yourself. It doesn't get much better than that.

Not to mention (not sure about Nissan VQ's, like I said, I am a newbie) there is the possibility of boring it out slightly while you are at it too and end up with more power.

 

Ide love to rebuild but i dont have another car or a garage where i can work on it in.

 

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?

 

Hard to diagnose without an actual sound clip.

 

it would be hard to pick up

 

Worth a try

 

I just put a 2 gig card in my cam, it records video and sound, Ill try to get one up here tomorrow , i hope it can pick it up.

 

Here is a video clip of the sound, also started working on painting the tails. looks good now that its done.

http://www.youtube.com/watch?v=OZW2lprSyNU


At first i have the middle injector unhooked wich makes it louder, you see when i plug it back it its not as bad.

 

Has anyone checked the vid?