Gas mileage dropped 50% with some mods? WTH!!!!!!!

[Travis1461]

Hi everyone I own a 91 ranger xlt 2.9 4x4. I just recently did the new mazda tranny swap, put a brand new fuel pump assembly unit in and new bigger 4.0 clutch and flywheel. I also knocked all the crap out of the cat and so the exhaust flows free without the cat restricting it. I usually get around 18 to 20 miles to the gallon but after doing these few things my mileage is around 9-10. I don't get it, could the Fuel pressure regulator be a cause?

 

[rusty70f100]

You must have forgot to plug something back in. O2 sensor perhaps?

 

[ranger]

Gutting the cat is not good that will lead to loss in fuel mileage. The stock cat flows free enough for the 2.9 o2 sensor is another thing to check.

 

[disciplerocks]

Did you reset your ecu?

 

[Strieg]

Yeah gutting the cats prolly didn't help too much..
The engine is set up to run with back pressure from the cats... As long as they weren't clogged or plugged, you prolly shoulda left them.
But it does also sound like the o2 sensor (as mentioned ^^^) you might be running REALLY rich.

 

[Travis1461]

O2 sensor was plugged in and I reset the computer and everything. I always heard on here gutting the cat would increase power and my ranger has been lacking power for quite some while thus the transmission, clutch, fuel assembly, tps sensor, gutting the cat replacing other components. Nothing seemed to help much. The tranny did do a little in the lower end but still lugging on power on small inclines 10-15 mile an hour drops in fifth and barely holding speed in 4th. It has 220k on it but compression and fuel pressure and everything seems to read good. Only questioning fuel pressure regulator because when doing psi check on fuel rail unplugging vacumn line had no affect which I hear is supposed to raise the psi?

 

[rusty70f100]

Vacuum at the fuel pressure regulator is supposed to lower the pressure in the fuel rail. If the pressure didn't lower at all when you unplugged it, then that could be a problem.

How much pressure does it have (in PSI)?

 

[BII Plow Truck]

Gutting the cat is not good that will lead to loss in fuel mileage. The stock cat flows free enough for the 2.9 o2 sensor is another thing to check.

I agree, cats don't take hardly any horsepower like they did in the 70s.

 

[Strieg]

my ranger has been lacking power for quite some while

Our trucks really don't have that much power to begin with. Are you sure your not overestimating your trucks stock potential?

 

[ranger]

I don't think he is overestimating alot maybe a little but I have 4.10s and 33's and I can hold overdrive on the highway fine I might have to shift into 4th sometimes but as soon as I do I pick up speed again. Your motor might just be tired and it might be time for a 4.0

 

[Travis1461]

Thanks for all the replies everyone. I'm gonna try and replace the fuel pressure regulator if I can find a cheap one. Mine is a threaded fuel line so of course its more expensive but a junk yard might be the way to go. I'll post what I find. Cant remember what the psi read but it was in the norm when I checked it a while back.