96 Lumina poor performance when cold

[Sealant]

Very hard to start (must turn over for long period before starting) then sputters for a few seconds until it clears up and runs fine

Service engine light came on, took to Auto Zone for code check which indicated bad MAF sensor and lean mixture (O2 sensor). Replaced both and car runs great even when cold but the starting problem remains.

Seems to be good fuel pressure.

Any ideas?

[manicmechanix]

Are you sure the fuel pressure is good? It needs to build to spec almost instantly and hold pressure. A bad fuel pump drainback check valve or a fuel pressure regulator bleeding off too much pressure could cause this. Also have you checked the spark plugs and wires? fouled or worn plugs can cause hard starting. Also check for vacuum leaks. Other than that cleaning the throttle and replacing the pcv can help starting.

[Sealant]

Originally Posted by manicmechanix

Are you sure the fuel pressure is good? It needs to build to spec almost instantly and hold pressure. A bad fuel pump drainback check valve or a fuel pressure regulator bleeding off too much pressure could cause this. Also have you checked the spark plugs and wires? fouled or worn plugs can cause hard starting. Also check for vacuum leaks. Other than that cleaning the throttle and replacing the pcv can help starting.

I don't have a fuel pressure guage so I don't know if the pressure is to spec. All I know is that there is some pressure in the fuel rail when I open the valve.

Where is the drainback check valve? is it part of the pump in the tank?

Thank you for all the other ideas as well. I'll try them next.

[Sealant]

I guess I should have checked back a few posts. It looks like me and BigshotBill have a lot in common.