Hey I have this crappy car and the C.E lightis onand thecode was for being too lean. But when I have Mitsubishi check it they tell me that the problem is a cracked exhaust manifold. Now when I ask them if replace it will the car run right? "Only if that isthe only thing wrong with it" the dumbass replied. How the hell does exhaust cause a car to run lean?

 

If the manifold is cracked, oxygen is gonna go into the exhaust and the o2 sensors and going to pick it up and read lean.

 

Then would it also be causing the car to run like crap?

 

Yep, my old 1gen had a cracked manifold and it would stall when it was completely warmed up. I fixed the crack and my symptoms went away.

 

It is a general reply, but without actually doing a thorough diagnostic, that sounds pretty straight forward to me. You'll find out soon enough that some things work within this domino effect.
Yes, if the front o2 sensor is reading lean, the computer tries to compensate by adding more fuel, your MPG deteriorates, your car runs bad. So, it's really not a dumbass answer, just a general answer and unless, you pay for it, that's usually all they're going to give bro. They have to make money somehow.