exhaust manifold leak

Unless you know for sure both manifolds are leaking, doubtful…You can check by plugging up the exhaust. To trip lean code on exhaust it usually needs to be a pretty major leak. Being that it’s complaining about both banks, very unlikely, but here you go just in case:

I’d be searching for some other leak beyond the MAF sensor as it’s likely something common to both banks, cracked hose, etc..

If you have access to a scanner. Check if the freeze frame to figure if the issue is at idle or when loaded. Most of Ford problem with lean code I found are related to vacuum leak.

A smoke tester will show the obvious. Then spent the time to look and press with your finger the rubber hose… with time they loose their hardness.. so you can squeeze them shut. Strong vacuum would collapse them. The pcv hose would be the best example.

Absolutely, a leaking exhaust manifold can cause those codes. Those codes do NOT mean the O2 sensors are bad, it means a lean condition has been detected. Do not replace O2 sensors when you have those codes. Exhaust leaks can cause O2 sensors to read lean. So if you have those codes and a know exhaust leak, fix the exhaust leak, clear the codes, and see if they come back. More info on how O2 sensor work in this video.

More information on solving performance problems here.

http://www.ericthecarguy.com/faq/solving-automotive-performance-issues

Good luck and keep us posted.

Yes, if it thinks there’s a lean condition and is dumping far more fuel in. I would expect to see at least 2 on each bank, misfire wise, or a P0300, but it might just not be bad enough to register the rest as of yet. Are you sure you checked all along the exhaust and IAC for intake? Is the idle ok? Stop it up, and run your hand along just off it, back to front, not just the manifolds.