Weird Resonance from 1.5k-2.5k?

I’ve got a problem, it’s intermittent and I cannot pinpoint the sound under the hood.

Basically, sometimes I get a real nasty, loud resonating sound from about 1.5k RPMs til 2.5k. The sound goes away almost exactly when the car reaches 2.5k RPMs.

The problem isn’t consistent either. It comes and goes as it pleases. I can’t seem to locate where exactly the sound is coming from, but it almost sounds like it’s from the drivers side of the engine bay.

All the vitals of the car check out A-OK.

Does anyone have any ideas that they could point me in as what to look for?

only under WOT?

partial throttle?

by resonance, do you mean vibration? is there any shaking or rattling involved? when i think of resonance, i think of sound waves be louder at a certain frequency due to the size of the objects they are bouncing off of, i dont know if this is what you mean or not…?

could it have to do with your turbo spooling up at all? how old is the turbo? maybe there is too much friction and it howls when it spools, but once its spooled it is ok? i dont know, im just taking a shot in the dark here…

more info would probably help.

good luck steve :tup:

Any throttle.

Turbo is about 50k now, no shaft play, spools great. Definatly isn’t that.

The noise is as if something is hitting against something else.

Check all bolts under the hood, especially anything attached to the firewall. I had a nasty vibration in my WRX from the time it was new, the dealer finally found it, it was a loose bolt on the firewall. Sounds similar to what you are describing.

I have the same problem but it comes from the rear… I can’t pinpoint what it is but it’s a high frequency rattle. And there’s this sound that comes from my engine thats pretty similar but I don’t know how to find it either. Just turn your radio up :slight_smile:

from what I remember of my 2G days… the exhaust manifold bolts would crack and cause this to happen. I was too lazy to check, and it didn’t seem like that could be the case, but people swore that was what it was.

I checked all heat shields and they were all fine.

i would say check any and all heat shields and bolts attaching them. alot of vibration goes thru your exhaust and anything loose will rattle like crazy.

serioulsly loose bolts anywhere, check motor mount bolts too, maybe its that excuse for shiftlinkage u have

I was getting a strange rattling as well for awhile on my car… got louder and louder … sounded like a belt squeeling almost… It only happend at and around the vicinity of 2k rpms… no matter the throttle %… turned out to be the catalitic converter heat sheild… I’d say check the heat sheilds…

Yeah, I’ve gotta owrk on the car tomorrow so I’ll try to find out what it is. It’s definatly something loose and the motor must vibrate just the right way at 2k or so to cause the vibration.

Hmm, well I looked everything over, no loose shields or bolts that I could find.

It is dependent with engine speed and the ticking gets faster as the RPMs rise, but then at 2.5k it all just clears up and goes away.

Also, the sound seems like it’s coming from the upper region of the motor, as best as I can tell.

so your saying its more of a ticking coming from internals of the engine? i cant say i know much about your motor but on my Z i have a noisy lifter which gives me a fairly annoying ticking that rises with the rpm’s. if thats the case ive been told using a heavier oil especially in the hot summer months will help but im just guessing without hearing the noise or knowing anything about your car good luck

Break out the po’ man’s stethoscope (screwdriver to the ear) and try to pinpoint it better. Don’t know much about DSM mills, do they use a tensioner for the timing chain? Weaker tensioners can rattle the chain against the covers.

The symptoms you are describing sound almost like rod knock if it was coming from the lower end, in that they only appear in a certain rpm range.

You forgot to check the one component of your engine that is supposed to control vibrations. Check your balance shafts and the associated belts. The shafts are getting ready to seize and/or the belts are on their last legs (hence the weird vibrations at low RPMs. They will get gradually worse heading to the 3000 range).

heatsheilds or loose exhaust bolts, ive got both right now causing the same problem