Flapping sound during acceleration

[shinjyo]

My 95 makes a small sound from the back like a flap rotating and tapping when under acceleration. It doesn't make that sound during idling or too obvious when rpm higher than 2800 rpm. The sound seem to go faster when the revs going up during acceleration.
The car looks fine, no leak, belts seem ok also.
I plan to take a look of the drivetrains, ball joints, CV boots, check the wheel lugs, intake box during oil change this weekend. Might check the valve adjustment when time permits or drop by Ramon to take a look.

Anything else you guys may suggest I look into? Such as fuel injector etc.

Thank you!

 

[cmthomson]

Could be the timing belt bumping against its case. I had a vaguely similar problem (diesel-like rattle at startup) that turned out to be the t-belt.

 

[docjohn]

bad wheel bearing?

 

[JD Cross]

Check to see if one of your CV boot straps has come loose and is hitting the shield

 

[TomCat]

"rattle"...engine knock.

 

[shinjyo]

Thanks for all the suggestions. It is not a loud noise and the noise doesn't happen at idling, only when the car rolls during low rpm.
I have a feeling it may require valve adjustment since the car seems to vibrate a little bit more than my previous 91.
Will update you guys once find out.

 

[RYU]

Take a video or take it a local meet if you want a peer diagnosis.

 

[silver2002]

Check for pebble / object jammed in tire treads. Check lug nuts.

 

[Speedmaster]

I have a similar sound (1997). Mine happens at low speed acceleration, is independent of the engine (i.e. goes away if clutch pedal pushed in, and at higher speeds). I suspect it is axle or transmission related. Mine sounds a lot like I would expect a rubber hose rubbing against the tire to sound.

 

[shinjyo]

A follow up to my post. I took a video hopefully to show the sound. I checked the CV joint, wheels, bearing. They all look fine. Ramon at Niguel Motor thinks it's the valve and recommend valve adjustment.

I tried to stay at constant rpm to emphasis the sound. My best description is it sounds like doh doh doh doh doh in the video. In reality, it sounds like a valve with far...far...far.... The sound frequency goes faster when rpm goes higher and the sound diminishes when rpm is above 4000 rpm. May be it's because the engine noise is loud enough to cover this sound, but it's quite obvious at low speed and low rpm. You may need to turn up the volume to hear it.

I may try to perform valve adjustment if time permits. But during the meantime, I am seeking advice to see if it is something major that I shouldn't keep driving.

http://vid10.photobucket.com/albums/a122/SunnyLo/03032241_4557.mp4

My video recorder also picks up a high pitch sound like wee wee wee, so you can ignore this sound since I can't even hear this sound in the car.