The driver was complaining of a check engine light and a rough-running engine at idle. I scanned and found a P0171. L/T trims were 29% and S/T were 24% and the engine ran noticeably rough at idle. At 2500 rpm, the trims improve significantly and are down to single digits. I did notice at idle that the MAF reads .001 lb (seems low) and the IAT seemed to be 20-30F higher than it should be, so I think this is an area that warrants further investigation.
However, I did a visual inspection and was advised to check for exhaust manifold cracks. As you can see above, this one is clearly cracked. Unfortunately this vehicle is outside of the 10/120k warranty extension.. I sprayed a hydrocarbon in the crack and did see the s/t fuel trim begin to slowly trend negative, so I think there is a small leak. I did not hear any exhaust leaks though, which is odd.
My question is this: would it be feasible to take off the exhaust manifold and have the crack welded? A new manifold is only sold with a catalytic converter, and in CA that assembly would list for $1100.
