That's the best way I can describe it. I can't hear it at idle, but when I accelerate there's a flapping noise coming from the engine - almost like there's a helicopter flying around in the engine bay. Really noticeable when cold, but only mildly noticeable when the engine is warmed up. Again, not at idle or cruise, but when accelerating.
Any ideas?

Thanks.

 

You checked for helicopters right? OK then, it could be your exhaust studs. Can you hear it if you have the car in Park/Neutral and just blip the throttle under the hood (presuming that you have the hood open)?

 

it'll likely to be the exhaust manifold studs man....if you get to hear my car before i get them fixed i'm sure we'll sound like twins

 

It could also be the lifters. That is the deal with mine. I took it to an auto shop and the guy told me that I do not have an exhaust leak (even though I have 2 broken studs) but the clapping noise was the lifters. He said that when I get my oil changed to put in 20W-50 due to the high mileage (169K) and put in a bottle of Marvel Mystery Oil.

I took it to Jiffy Lube and had the oil changed and added the Marvel Mystery Oil and OMG, I could tell the difference on the drive home. I am so glad that I do not have to fork out a couple of hundred bucks right now.

 

reygarcia - that's true.
i know for sure that i have a leak. but at first i did suspect the lifters to be making all the noise.

 

Marvel Mystery Oil is the fix it all around here..I use it as a pneumatic tool lubricant, diesel fuel anti-gel, break in oil for rebuilt/new small engines (LOW throttle), and I use 4 quarts of 50 wt racing oil and 1 quart of MMO in my truck..
However, I would have reccomended straight 30w or 50w racing oil and MMO rather than 20w-50, as the MMO allows the oil to flow like a light weight oil does, but if it helps, it shows how much learning from shadetree mechanics teaches a person..

 

OK, stuck my head in the engine compartment and revved the motor. The flapping noise is coming from the rear and I almost passed out from the exhaust fumes. Definitely not the lifters, most likely some sort of exhaust leak. Can I just tighten some bolts down there, or what? Thanks.