Hello,

Can a crack in the exhaust manifold make fuel go lean @ wot
The car is being tune for serveral week and everything was fine until the fuel go lean for some reason after several day of e-reflash.

I changed the fuel pump, check for boost leak ect... nothing was wrong.

Until I decided to clean the engine and store the car,waiting for my new FPR... I found a small crack on my DC manifold.

Wondering if this can be the cause?

Thank you.

 

Bump,


I'm in a similar situation, instead of a crack, I have a leak and/or possibly blown exhaust manifold gasket. I'm wondering how this would affect my tune until I get it fixed!

 

In my experience....I had an exhaust leak before the wideband which was causing my A/F to read lean. Open air leaking into the exhaust system caused this. And you could be tuning your car with false information from the wideband. Like giving it more fuel or retarding the timing when it may be just fine. Thus making you lose power.

 

On the same tune AFR was around 11.0-11.2 with 0-1 knock from 2000 - 8000 rpms.
Till it goes 12.0 AFR wit 6-11 knocks...

I only found out the very small crack 2 weeks laters.