Still running lean...

[ndrhew]

I've had a lean fuel mixture issue for some years now. I took it in couple of years ago to have it fixed. I had a bad timing chain (you could hear it). The mechanic said that replacing the timing chain would involve a lot of disassembly and the new gaskets used for reassembly would likely fix the issue. They didn't. I replaced plugs and wires, MAF sensor, the two O2 sensors before the catalytic converter, and the fuel filter. My Light came back on, and the codes were lean on both banks. When I start the car after a cool night or several hours in the cold it revs to about 3000 rpms and then dies, unless I give it gas. For the first several minutes of the day, it idles erratically, again unless I give it gas. I cleared the codes yesterday after replacing the o2 sensors and MAF sensor with the hope that wouldn't come back on. They did this morning with the same lean codes. It runs and starts fine if it has been driven earlier in the day or if it is warm outside. What could this be? It's driving me crazy!

 

[Jakee]

The first thing that comes to my mind is a leak somewhere. Intake gasket (between the upper and lower, maybe?) Hose came of or is almost off?

 

[steventadams]

Do a search for 00m12. It's a Ford kit that replaces your intake gaskets. They shrink when they are cold and so let extra air into the intake, giving a lean condition. Then when the car warms up the gaskets get back to regular size and everything is a-okay.