At or near WOT, a fairly loud fluttering noise is coming from engine compartment. Not always, but more frequently as days go by. It feels like the truck loses a little power when the noise starts. Any ideas? Thanks.

 

If its between 1st and 2nd,it's the four cylinder fart.

 

detonation perhaps?

 

I thought that was when the motor decreases the timing to make it easier on the transmission when it shifts.

 

Its not while shifting and it is not detonation either. it sounds almost like if you were to blow an air hose against a running fan, if that makes any sense.

 

That is exactly what the 3/4 drop sounds like but it happens during the one / two upshift. The computer controls this if you're still stock. The computer drops three cylinders for 4/10th's of a second to minimize torque on the transmission. A chip will stop that.

 

it happens in third gear while the truck is pulling hard and does not go away until i let off the throttle.

 

Before any logical answers are givin you need to list your mods, if any.

 

I had something like that, followed it around for a few months, finally turned out ot be the bearing on the S/C belt, dealer replaced the idler pulley and it cleared up. I would've never thought that one up, but it stopped it.

G

 

Just guessing...........loose spark plug??? Exhaust leak???

Dan

 

Thanks for the responses. I had a Chrysler turbo II engine and once the air intake boot to the turbo charger came off and it made a noise exactly like the one i am hearing in my truck. Oh... also truck is stock except for K&N panel filter. 13,000 mi.

 

Does it sound kinda like a kid ridding a bike with a clothes pin holding a plastic playing card in the spokes as he goes down the road? If so than you are experiencing some major Detonation and you need to stay out of full throttle until you get a new program and I would check my plugs if you have done this very much. You are running in a very lean condition kinda like pulling the lever on a cutting torch, when the O2 is put to the torch it gets real hot quick. You can melt the ends off your plugs very fast when your running under these conditions. I bet your moving pretty good and deep into the gas when you hear it start then in just a few seconds while trying to go faster it feels like your loosing power. The engine is starving for gas at the point.

 

Could it be your clutch fan??

 

usahooters, that is exactly what it sounds like. i live in Ca. 91 octane is the best i can get. my Ford dealer said it would run fine on 91, but then again it never made this noise with 93 octane. how can i fix this?