EdPDX

after replacing my IAC, PFE and EGR Vacuum ergulator, I cant figure out why I now have part throttle stumble. It feels like a vac leak; but the codes say Fuel pump primary circuit failure. I've checked the vac lines and dont hear or see a leak. The Throttle body "elbow" was removed and cleaned as well.

Under load (uphill) the car stumbles with a rough idle until I hit the passing gear, Then it seems better; but still underpowered.

anyone have an idea of what I want to try next?

EdPDX

92 merc Grand Marq. 4.6

tbird100636

Check the fuel pressure. It should be at least 30 psi. If it isn't then you may have a bad fuel pump. Slim possibility you may have a wiring issue.

__________________
Master ASE Certified L1 Chrysler Technician- still a Ford fan at heart.
1964 Thunderbird Hardtop- Chantily Beige- 390 FE 4V V8-Uncle's Car
1966 Thunderbird Convertible- Red- 390 FE 4V V8- Uncle's other car- waiting for paint and body work!!!
1967 Mustang Convertible- Blue- 289 V8- helping a friend re-assemble this classic

EdPDX

Well after lots of reading and testing with a multimeter I have not come up with the current demon. I have now replaced the:

O2 sensors
MAF
Temp Coolant Sensor
EGR
EVR
PFE
IAC

The hoses were checed for vac leaks- 2 Found:

EGR tube replaced for a split in the corrugated elbow.
PCV lower hose to intake manifold- the infamous "rubber 'T'" was bad and replaced.

Contacts have been cleaned and replaced at every connector that was disconnected.

PCV valve seems to shake freely.
TPS was tested as good

Past codes include:332 542 543 556 176 177. All have cleared with changing of various parts above.

Emmisions test at the state inspection station yesterday produceed expected results X NO PASS X Hydrocarbons and carbons too high.

Help... I'm about ready to see if changing the floor mats will help.

Thanks,

Ed