I've posted this question before, but decided to place it in the V8 section hoping to get some answers.

Problem:
During accleration from a stop, I hear a flutter sound coming from the exhaust. I can also feel it! Once the truck gets going, it goes away and the truck runs, sounds and feels normal. Once the truck has been running for about 15 minutes, the problem is gone and I don't notice it during acceleration. The best way for me to explain the feel and sound, is similar to trying to ride a dirtbike with the choke on or riding it when the plug fouls.

Truck Repairs last 4 months:
- Replaced plugs
- Changed transmission fluid
- Replaced fuel filter
- Replaced air filter
- Replaced exhaust manifold (passenger side) due to leak
- Cleanced Throttle Body
- Cleaned MAF Sensor
- Installed Flowmaster 50 Series SUV single in/dual out side exhaust
- Replaced both Cam Phasers
- Replaced Oil
- Replaced anitfreeze

Still have the flutter problem! Truck isn't throwing any codes. Mileage is 96K and using Edge Evolution II programer. I've even put the programer back to stock and removed it, thinking it had something to do with the problem. And it didn't.

I'm at a complete loss as what to do or look for next. Could it be COP's, EGR Valve, Catalytic Converters, Oxygen sensor???

Hope someone can help?

 

Is this a 4.2 v6? if so it could be one of the secondary intake runners I'm not real familure with the 4.2 only worked on one once but I know those runners can make a flutter noise if they are not functioning properly. They also open after the truck gets warm which may/ should change the sound.

 

It is a 5.4

 

When you said you decided to put this on the v8 site I just figured you had a v6 and didn't get a response over there on that site. Did the flutter start after you did any of the changes you listed above or was it there prior to all those changes?
Do you get any smoke out the tailpipe or any unexplained loss of coolant?
Is the flutter noise related (speed up and down with RPM) to the engine RPM?

 

I mainly noticed after I had the exhaust installed. I called the place that installed it and of course they said it wasn't anything to do with them. I didn't want to say it was the exhaust at first, because I'm not sure if the problem was already there and wasn't as noticible with factory exhaust. But with the new exhaust, I'm wondering if it just magnified the problem.

I don't notice any smoke from the exhaust or any loss of coolant. The noise is only noticible after truck has been sitting a while and only during acceleration from take off. Once it has been driven a while, it seems to go away. I did notice this morning, that when I reach about 40mph and the truck shifts, it goes away and the truck seems to accelerate normal. So, I guess it's safe to say that its only noticible from 0-40 mph and during a cool motor.

 

I usually suspect anything that was installed or changed and after that activity there is a strange noise or drivability issue. We would always ask the question (what changed) when we had a engine start running bad that had been running good, start making a noise, not making power, etc. I would put my money on an exhaust leak somewhere in the new exhaust system. A flutter could very well be an exhaust leak somewhere.

 

It's funny you mentioned the leak. I contacted Flowmaster earlier today and they said there could be leak somewhere in the exhaust from when it was installed, or there could be a good chance there is a bad weld in the muffler itself and when the muffler is cold, air leaks in, but when it heats up, the leak seals itself. They said if it's a bad weld, they'll replace for free! Already contacted the muffler shop and I'll be heading there soon.

 

Maybe the donut gasket at the end of the exhaust manifold. Sometimes they seem to swell with heat, stopping the sound.

 

Took it to the place that installed the mufflers and they said leak is where the y-pipe connects to the manifold. Metal on metal causes this. They are going to fix it Thursday. I'll let you know the results soon.

 

Trucks back from shop...........Although its a little better, there is still the flutter during acceleration! During this accelertion, the truck is very sluggish, sort of like it's running rich... Any other suggestions? I'm at a complete loss right now.