Crack in both Exhaust Manifolds, should i fix it now?
The Gaskets are tight.

the Cracks are acoustic noticeable during acceleration...
If u know it,
I know it so i hear it.
but what could happen?

is it bad for Engine?
in this area is nothing that could be damaged through hot air.

 

It will affect your fuel economy. The sooner you fix it the sooner you'll get better MPG.

 

im having sorta of the same issue. Both my manifolds are rusted to hell, have a stud broken on one side and two on the other, and the right rear cat is leaking.... about a $1200 fix at a shop. Im just going to wait and do it myself.

 

i have 17.2 MPG (roundabout) and no more Lambda correction
(i have the Wrong Air Problem fixed)
It seems that the Cracks have no affect to the lambda Sensors.

 

THe sound is enough to drive me crazy. Do them yourself though! Sure its a huge hassle, but beats paying a dealership to do it

 

I'd be surprised if this is the case-I'm not saying you're wrong. But any time a pulse of exhaust leaks out of the manifold, a pulse of ambient air leaks in. Because this is so close to the o2 (lambda) sensors, it will almost always have some affect. If you can access the datastream I'm betting you'll find the long term fuel trim is adding fuel.

 

I had a Long term Fuel trim on the Right bank, but this was caused in a Leaking PCV Valve Grommet.
Now the banks are quiet similar in Lambda Parameters in Short also long term Fuel trim.

 

What would a cracked manifold sound like?

 

pfpfpfpfpfpfpfpfpfpfpfpfpf
during Acceleration
not as loud as the Exhaust it self.
But when u know it, u hear it.
same sound like a untight Exhaust manifold gasket.

 

It almost sounds like a valve pinging, getting faster as you accelerate