2000 Mercury Mountaineer 5.4L throws code P0171 P0174 hesitation, lack of power, lurching. If I stop shut off the car and let it sit for 20-30 minutes it starts back up and runs better. But this only takes place when car is under load going up hill when the outside temperature is ~80deg F. This has happen several times in the last couple years. The hesitation is like the EGR valve is open but I if that were true I would throw a code for excessive EGR flow P0402. When outside temperature is <80 there are no issues driving under a load.
1. Disconnected the vacuum line to EGR and drove vehicle 9 miles received a code P0401 insufficient flow which I expected because the EGR vacuum line was disconnected. So this told me the that the PDFE module was working along with the Vacuum Solenoid that opens to operate the EGR valve is working also.
2. Replaced fuel filter, vacuum checked and cleaned EGR valve all good. The EGR was very clean.
3. Checked fuel pump pressure with gauge connected key on engine off 5psi was reading. Turn key off then wait 10sec then turn key on again pressure increases by 10psi each time 10psi gains to 60psi.
4. Bled down pressure in fuel rail then started engine and pressure gradually increased to 60psi. Left engine running and disconnected the line from the fuel dampener rear of engine. 5. Shut down engine then repeated fuel pump pressure test. Key on engine off, pressure jumped to 60psi immediately. Bled down pressure in fuel rail then started engine and fuel pressure jumped to 65psi. So I am not sure if I might have a possible bad fuel pump or dampener.
1. Disconnected the vacuum line to EGR and drove vehicle 9 miles received a code P0401 insufficient flow which I expected because the EGR vacuum line was disconnected. So this told me the that the PDFE module was working along with the Vacuum Solenoid that opens to operate the EGR valve is working also.
2. Replaced fuel filter, vacuum checked and cleaned EGR valve all good. The EGR was very clean.
3. Checked fuel pump pressure with gauge connected key on engine off 5psi was reading. Turn key off then wait 10sec then turn key on again pressure increases by 10psi each time 10psi gains to 60psi.
4. Bled down pressure in fuel rail then started engine and pressure gradually increased to 60psi. Left engine running and disconnected the line from the fuel dampener rear of engine. 5. Shut down engine then repeated fuel pump pressure test. Key on engine off, pressure jumped to 60psi immediately. Bled down pressure in fuel rail then started engine and fuel pressure jumped to 65psi. So I am not sure if I might have a possible bad fuel pump or dampener.
Mar 18, 2015 at 11:48 AM
