i recently bought a 1993 honda prelude 2.3L dohc, the car has a knocking sound when you first start it up for about 5 seconds then goes away, but then returns between 2000-3000rpm's. The car has plenty of power and drives great, i pulled compression on motor and all were in spec only one was about 10psi off. I'm hoping someone can shed some light on this problem if it is a major or minor. Otherwise I might need a new engine lol. thanks for your help!!!

 

Well......Hmmmmmm............. usually piston slap is a sign of collapsed oil wiper rings and the engine will have some oil consumption.
Kinda hard to "hear" the noise over the internet LOL.
Usually a main bearing will be a 'heavy' knock and continuious.
Rod bearings can come and go and are 'lighter' knocking.
If you can make the noise by going on and off the gas, and as the revs change up and down, I'd lean toward a rod bearing.
But Honda is famous for valve train noise when cold, but you should be able to locate the noise by using a long screwdriver as a stethoscope to see if its from the block or head.

 

thank you very much for your input, now i have somewhere to start.

 

Scrap piece of garden hose up to your ear makes another type of poor-man's stethoscope.

With either type, don't get caught up in the spinning drive belts...

 

What did you find out about this? I seem to be having the same issue, I'll change the oil tomorrow to maybe synthetic. I created a youtube vid here >


http://www.youtube.com/watch?v=Kj2thVW2odo

Driving me nuts! I've babied this engine. Why on earth does it sound the way it does????

 

that kinda sounds like mine but mine is a little bit louder. But the prob. I have with mine is it started out you could hear it @ 1st when you start the car. But if you rev to 3 grand and hold it for like 15-20sec it goes away. But every now and then you can hear it while driving only when you accelerate. My friend had a spun rod on his h22 and this dosent sound the same to me. Maybe hear in a bit I will make a vid to see if anyone can tell the diff. between the two (valve tap or sun rod)

Another question when you have a spun rod how can you tell besides listening to the motor?? I was TOLD you can change the oil and strain the oil through a bunch a paper towels and see if there is any shards of metal...is this true?? B/c I have done the oil straining and didnt see anything but oil.

 

For $30 you can send an oil sample to be analyzed. High copper or zinc or silver or whatever can tell you there's damage to a journal bearing somewhere. May not be able to differentiate between mainbearing vs. rodbearing, but either way the bottom end has to come apart.

But you've already thrown out that oil?

 

I think I still have it. Where would I send it off to?

 

blackstone-labs dot com
I'm sure there are competing places that do oil analysis too.

But now you're also analyzing everything that has come from the pan you drained into. And the old bottle you poured it into. And anything else that fell off your oil pan into the old oil...
Blackstone has an FAQ page that tells you all about it.

And also check out bobistheoilguy dot com for way more oil information than you ever thought you could possibly be interested in.

 

ok I will check it out. Thanx for all the info and such!!
I hope its valve tap and not spun rod.