Have an 2010 Acura TL J35 engine ive recently rebuilt because the ring lands broke on cylinders 5 and 6.


had the block and heads milled but not sure how much they took off.


Runs great until around 4500 5000 rpm and makes a rattly noise kind of like detonation but I'm wondering if when it goes into vtec if the valves are hitting the pistons. It wont go over 5000 rpm now, and it wouldn't before the rebuild either.


If I rev it up with no load it doesn't make the noise but it still wont go over 5000 rpm.


Any ideas? Oh and I never found a reason for the broken ring lands.

 

I'd ask the machine shop how much they took off. Generally with just a resurface, they take off as little as possible like a few thousandths of an inch unless specified otherwise.
I don't believe the stock (auto I presume) ecu will let you free rev to redline without an actual load.

Does the noise sound kinda like little bbs in a coffee can?
Can you kinda control the noise with throttle position in those rpms?
Have you tried higher octane fuel?

 

I run Shell V-power93 octane fuel, and it sounds more like rods knocking but as soon as it starts making the noise at 5000 rpm I let off the pedal and it goes away.

 

What happens when you creep up on 5k rpm with low throttle input?
What is the vtec engagement point on your engine/ecu?

 

Broken ring lands is usually related to detonation and excessive cylinder pressure spikes.
Since you think it may be detonation your hearing, I would try a few things to see if it is.

IDK if you have access to any type of scan tool, but if you can bring up your knock sensor value and log it, this should be an easy diagnosis.
If not, get yourself higher octane gas like 100 octane or so. When your current fuel level gets almost empty, put in a few gallons of the high octane stuff...
Then go for a drive. If the knocking sound your hearing goes away, then you have a detonation problem.

This is an auto trans right?

 

A sound clip would help but I know it may be difficult.
Ziptie your cellphone in the engine compartment and go for a ride. If we can actually hear it I'm sure someone here will recognize it.

 

Hey Guys Sorry I was away for so long.


Found the problem. It was a clogged catalytic converter. Only $600 Dolla and no more rattling valves or occasional smells of hot antifreeze. Engine revs to redline no problem now. No more weak acceleration and strange shifting. Its a ******* race car now!


Thanks for your help!