preludeToPower

Hey all. I just got a 1990 Prelude SI, and at about 2,500 - 3,000 RPMs there a metal vibration type noise coming from the engine. Has anyone had the same problem, or know what it is?

Civic Type Sev

It's really hard to say what it is exactly. It could be anything. You'd probably want to have someone listen to it and try to locate it from outside the car while you rev it up in that 2500 to 3000 range.
I had a similar problem a couple of months ago and it ended up being the hood latch that had slid up causing the hood to vibrate at around 1500 to 2500 rpms. All I did to fix it was to loosen the mounting screws for the latch, lower the latch a little and then retighten the bolts. Note that the rpm could be different on yours since the weight and stiffness of the hood will affect the frequency range in which the hood will vibrate. A quick check to see if this is the problem is to have someone apply pressure on the hood while you rev. If this stops the noise... you've found the culprit. If not then keep looking. It could also be busted motor mounts, lack of clearance around the air intake tube or interference with any other aftermarket components.
good luck

preludeToPower

Thanks for your advice. It sound as if it's coming from the front of the engine, for instance around the heat shield for the exhaust manifold. But evertime I walk around a diferent area and rev the engine, it always sounds closer to me. Is it possibly something loose under the valve cover can make that kind of noise?

Civic Type Sev

I really doubt it's something inside the engine. Did you try and remove the heatshield. Alot of times these rust out and end up vibrating quite a bit. Happened on my other engine (D16y7) so I just pulled it off. Also... do you have an aftermarket air intake system??? if so you should check to make sure it's not touching anything else in the engine bay that it shouldn't.
And by the way.... how do you like your ride other than the vibration. I bet that thing hugs the road like nothing else with the 4ws. I've been looking to get one for a while now but all the ones I see up here in Canada all have too much rust for my liking. I may go down to the states to pick one up later on.
Good luck finding the rattling noise.

preludeToPower

I don't have an aftermarket intake yet. I tried removing the heat shield, but I have to remove a hose for the power steering to get it out. That will be my next venture.

As far as the handling goes, I'm still getting used to the car. Right now it has a leak in the hydraulic clutch line. So until I get the fixed and feel comfortable with the car, I won't have a good feel for it. But from what I'm seen so far, it's just a wierd feeling. Because it does two different positions depending on how far you're turning. If you turn a little bit, the back wheels turn the same direction, keep turning they straighten out, and then turn the opposite direction. When it's in better working order I'll experiment with it more and let you know.

Again, thanks for your continued advice.

preludeToPower

Found out it is the exhaust downpipe. There's a pipe inside a pipe, and it starts vibrating after a while. So you either have to cut 4 slots and weld it, or buy aftermarket.

Civic Type Sev

Cool... I'm glad you found the problem. :thumbup: Let me know how you like the handling when you get that line fixed. So what are your plans for the car? Any near future mods planned?