Engine Performance problem
1999 Honda Accord 4 cyl Front Wheel Drive Manual 205000 miles
----------------------------------------------------------------
The car runs great, but when you first start out when the engine is cold the car wants to stall when you give it gas. It doesnt die and will slowly climb in RPM and then when it hits 3500 rpm it just comes alive. You can feel the engine "hunting" a little until it warms up and then it runs like a top. The check engine light comes on and stays on and the only codes are P0170 and P0171. Occasionally the light will go out for a couple of days and then its back on constantly, right from start up. When I reset the light it will come on right about the time the engine reaches operating temp (about3-4 miles of driving). I have replaced the fuel pressure regulator, spark plugs and wires, dist cap and rotor, pcv valve and cleaned the IAT (lots of crud), cleaned EGR as well. I've done the Seafoam treatment too, multiple times, and cleaned the throttle body. I've have soaked the engine with ether looking for a vacuum leak and replaced the gas cap. Once the car warms up, it runs like new with the exception of the check engine light. Problem still there, any suggestions...do the two problems (cold running condition and dtc) seem related with a common cause or are they most likely 2 separate problems. When does the oxygen sensor actually come into play? If it is ignored in open loop, then what would cause the hunting/stalling problem? HELP PLEASE!!!

Test the coolant temperature sensor this is the one that controls fuel delivery during open loop before the snitcher oxygen sensor takes over in the closed loop mode. Also check the throttle position sensor

P0171 is a lean fuel condition can be caused by:

* Low fuel pressure due to a weak pump or leaky fuel pressure regulator. (use a fuel pressure gauge to check fuel pressure at idle)

* Dirty fuel injectors. (try cleaning the injectors)

* Vacuum leaks at the intake manifold, vacuum hose connections or throttle body. (Use a vacuum gauge to check for low intake vacuum)

* Leaky EGR valve. (Check operation of EGR valve)

* Leaky PCV Valve or hose. (Check valve and hose connections)

* Dirty or defective Mass Airflow Sensor (MAF). (Try cleaning the MAF sensor wires or filament with aerosol electronics cleaner. Do NOT use anything else to clean the sensor, and do not touch the sensor wires)