What’s the cause of exaust sputtering?

Hey guys,
My exhaust is sputtering? What are the possible causes? I thought I fixed all the exhaust leaks.

here’s the video

https://youtube.com/shorts/P7fvD7YXVzA?feature=share

thanks!

 

Sometimes that can point to a mechanical problem inside the engine like a valve. Put a vacuum gauge on the intake manifold and see if it has 18-21 inches vacuum. Does the needle fluctuate? It should be steady

How does it run? Do you have any rough running or misfires?

Take away the fuel and spark and a engine is basically an air pump. The flow of air through the engine and out the exhaust should be smooth and always in one direction. When a valve issue develops (like not seating properly) the airflow out the exhaust can "suck back in" for a very brief second and make it sputter.

A backyard trick is to hold a piece of paper gently against the exhaust and see if it sucks back against the exhaust pipe for a split second. Like the exhaust is going backwards back up to the engine. That would be an indication of an internal valve issue.

 

Oh wow! Ok. I tried the paper trick. It didn't suck backwards at all. The pressure was only moving out of the tailpipe. I'll have to try the pressure gauge. Can you use it on the intake or does it have to be on the intake manifold? I'd have to take apart the assembly to get to the manifold right?

Is it possible that the exhaust leaks are not fixed yet and that's what's causing the inconsistent pressure at the tailpipe?

Thanks!

 

A vacuum gauge would be connected at any port on the intake manifold, the black plastic assembly under the engine cover

 

Thanks! I’ll try this and report back

 

Exhaust comes in waves or pulses from the individual cylinders firing, it's never like a compressed air hose where it's always flowing 100% all the time.

 

Oh really? Are you saying this “sputtering” is actually normal? I’ve already done a combustion leak test and it was negative.

 

This.

Its normal for the exhaust to do that.

If the truck is running good and you have no CEL, you are fine. Don't stress it.

 

Thanks! I might just do the pressure test as an excersise but otherwise I’ll just focus on the exaust leaks being fixed.

 

I found hairline cracks along the merge near the exit flange. They were barely noticeable but when the exhaust flexes with the engine within the chassis it makes it louder at certain times than others a quick weld fixed it up

 

Are you talking about on the bottom of the exhaust manifold?

 

At the y pipe section which is after the manifolds. The two banks merge into a "y" and if you look at the inside of it you may find cracks. It's a very thinly welded area from the factory.

 

Exactly. It's not a turbine engine, it doesn't have continuous combustion. If yours is a V6, that means that there should be 6 pulses for every two full revolutions of the engine—so at idle, let's say 600 rpm, that means each cylinder is firing 5 times per second, so there should be 30 pulses per second out the exhaust (there are variables that can affect how many you "feel" if you put your hand up to the exhaust, but that's the gist).

If the "sputtering" is inconsistent or jumps around I'd say you have an issue, but, as others have said, if all else is green, that sputtering is normal.