Cracked exhaust manifold

[gates6297]

Dumb question. Would a cracked exhaust manifold cause idle issues and lean out?

 

[99OZDSM]

Yes. It would mess with the A/F readings your front 02 sensor is getting.

 

[jakk220]

Not too sure that it would cause idle issues, but it would create a lean condition on your 02.

 

[99OZDSM]

It could create an idle issue depending on the severity of the leak. The front 02 sensor works in closed loop operation, which is at idle/cruise conditions. Open loop is under boost conditions and ignores the 02. Basically the front 02 sensor determines the AFR leaving your engine, sends this information to your ECU, and the ECU decides to either add or subtract fuel. So if the reading at the 02 sensor is not accurate, it won't subtract or add the right amount of fuel.

 

[gates6297]

Thanks for the info guys. New manifold on its way.