Low economy at citi???

[Col Flashman]

I can only re-enforce what S/S has just stated about the Exhauste being plugged.

And just For Your Information, the proper terminology is I-6, as in Inline 6.
The L-6 is the Flathead 6 designation because of the way the Valves are setup in the head in an L configuration.

[javi2001]

hummm interesting point, I'll check that. Any more ideas guys?

[optikal illushun]

how long ago was the oxygen sensor replaced?

[javi2001]

Good point. 2 or 3 years ago.

Injectors were cleaned 3 months ago. Engine doesn't hesitate, no rough idle, no black smoke, no any failures, it runs fine but is using too much fuel and condition is getting worse every week.

[chrono4]

Have you checked your fuel pressure? if the bypass regulator is stuck/bad, it can ramp up fuel pressure and blow through the injectors, resulting in a rich condition and very poor mileage.

[chrono4]

And to add to what I originally posted: A bad regulator would also explain the highway mileage being so much better than in town. You use more fuel on the highway, so it was being burned more efficiently, but as the problem got worse, it can't burn all the fuel, even under load on the highway.

[javi2001]

Heu Chrono4, that's a very good idea. I don't have tester for fuel pressure, but I'll check next week.

Thanks a lot...

[chrono4]

No problemo. We're all here to learn and be learnt.

[javi2001]

Ok guys finally I got pressure readings...

It has 49 - 50lbs engine runing idle
it has 59 - 60lbs engine runing idle AND vacum line disconnected from pressure regulator

And 60lbs Engine off fuel pump on

It looks a bit high, isn't it? what's the normal press. for 4.9's

[srercrcr]

.....but you'd see black exhaust (unburned fuel).

[javi2001]

Ok, there is no black smoke.... yet......

but it smell like unburned fuel.

I left installed the pressure gage for all weekend and I notice also, after stoping engine, pressure is reduce slowly to 0 psi in about 3 hours, I wonder...


How often the injectors can leak fuel? maybe they have to much wear and are leaking fuel to intake manifold???? causing the rich condition and the high idle also...

[javi2001]

Any more ideas guys?

[Motorhead351]

Maybe make a list of what you have done.

Plugged catalytic converter/exhaust was mentioned but it wasnt clear if you even had one or if it had been checked.

Are you able to pull codes?

[Conanski]

Yes, have you pulled the codes? See Ford Fuel Injection for a DIY method.

[SR_Crewchief]

Are you still running 95 octane? If so Why? If available, try 87-89 octane...once you've replace the knock sensor that is.

Have you pulled codes recently? If your getting sensor related codes verify that the sensors in question are functioning correctly. Since your fuel pressure appears to be good, then the problem usually relates to bad data been delivered from one or more sensors.