Replaced Power Steering Pump - Now Have Awful MPG. Suggestions?

1998 3.4 4x4 5-speed manual

Have always averaged around 21 mpg (lest winter gas). Doesn't matter if I drive mixed highway/city, highway or city. I've had this truck for over 15 years and have put over 160,000 miles on it. Almost like clockwork every 1/4 hashmark on the fuel gauge would register a 100 miles on the trip meter, eg: 3/4 full: 100 miles, 1/2 full: 200 miles, 1/4 full: 300 miles... and I would end up with anywhere between 300 and 320 miles range.

In December I had my friend's shop replace my power steering pump and flush the reservoir screen. Ever since then I'm averaging about 17 or 18 mpg (winter gas, summer gas, doesn't matter). My range is about 260 miles to 270 miles. It's brutal.

It is way too coincidental to me. It literally was the tank, and every ensuing one, since the power steering pump was replaced.

I asked my friend about it and he says there's no correlation. And that they would have to start diagnosing.

Any one here have any suggestions for me to look at? Does this pump run off a belt? Could the belt be too tight? Could wrong fluid cause this (see note #2 below)?

It's about time to clean the MAF and TB but truthfully I went 85,000 miles without doing it prior and my fuel economy didn't change once I did do a full cleaning of both.

Notes:
1.They used an aftermarket reman'd pump.

2.Haven't confirmed if they used ATF III fluid. I recently read here that our trucks require ATF III in power steering pumps. Don't know if that applies to non-OEM pumps or not.

 

how long has it been? maybe the ECM hasn't had time to reset or needs to be reset

 

This is weird. First thing in my mind is a belt that's too tight, but that would only wear out the pulley bearing, and belt, me thinks. Was the battery disconnected when the work was done? Maybe try resetting the computer by touching the pos/neg cable together for a few minutes. Very odd indeed.

 

I don't think the battery was disconnected. But it's been approx 3000 miles since the pump was replaced. I'm sure it would have reset itself by now.

I'm hoping the pump just isn't right and it's the cause. I have a feeling it's something else though.

 

How old is your primary o2? If it's original then buy a new oem sensor they get old and stop switching fast enough and cause a drop in mpg

 

Been hitting the coffee cake and donuts a little hard lately??

 

Are there vacuum lines running to the p/s pump on that model year? If so did the get hooked back up? May have a vacuum leak if they didn't, unmetered air = more fuel, may not be enough to trip the mil but enough to to get your fuel trim up closer to upper limit

 

I just looked at my records. I replaced the bank 1 upstream O2 sensor at 173,000 miles. That was 20,000 miles ago.

I bought the Denso OEM one off of Rockauto. But one of the studs was seized to the nut so when I backed it out, the whole stud came out. When I replaced the sensor I just tightened the whole stud/nut back down as best as possible.

I don't think caused an issue because I was getting my normal mpg after the sensor swap (and before the PS pump replacement)

 

It's ironic but my gym time has decreased significantly as this problem arose. But I hope to god that's not it.

 

That was one of my first thoughts, but I haven't had the time to investigate any vacuum lines being disconnected. I'll snoop around tomorrow if I can.

 

e-brake not fully released? hey, I know its unlikely but I have seen crazy shit like that lol.

 

Ok but is is still mounted good?

 

Take the belt off the pump pulley and spin the pump by hand, binding or tight? Is there a crank timming sensor around there they could have hit?