I have an original ap1 with around 130000km on it. Bought it about a year ago. Using Honda 5w40 hfs engine oil.



I am hearing a knocking/tapping sound from the engine during acceleration and constant driving around 3500-5000 rpm. Maybe the tapping is still there after 5000 rpm, but the engine noise is too loud to hear it. The sound is loud, especially when driving next to a wall or something the sound can bounce off from. I am not sure this sound was there when I bought the car, but I became aware of it not too long after.



The sound is only present while pressing the gas. As soon as I let go of the gas the sound disappears. The sound is not present at idle, although the sound can be present while gassing and not being in gear. I attached a couple of videos for reference. Worth mentioning also is that on a cold start there is an engine knock for a couple of seconds and then disappears. I haven’t noticed any loss of power.



After countless threads on s2ki most common issues that comes up is valve adjustment, failing timing chain tensioner, bad pulley bearings and what I fear the most rod knock or wrist pin failure. I believe the sound would still be present when letting off the gas if it where to be one of the last two, but I am no expert.



Currently I have had a valve adjustment done at a Honda workshop, then I changed the timing chain tensioner (to a Toda aftermarket one). None of these made any difference. I read that s2000 fuel injectors can be loud. I changed them as well to new oem ones, but made no difference to the sound. I feel the sound is too loud to be fuel injectors. I tried running the engine without the serpentine belt and giving some gas and the sound was still there.



I guess this sound is not normal? Do others that have S2000’s experienced similar? When I had the car to the workshop I asked them about the sound and also if they could do the valve adjustment to see if that would change the sound. They couldn’t diagnose where the sound came from and I ended up bringing the car back after the valve adjustment.



Any help would be much appreciated

 

That sure sounds like rod knock to me, could also be the wrist pin but it's definitely a bottom end sound because it has that deeper knocking noise instead of a ticking top end noise.

 

sound like rod knock,would stop using it !