New to barn 4.0 with Bad 5.7 MPG Needs Serviced

[Jay11]

1999 4.0 4x4 XLT EXT. CAB 84k miles

I picked up this truck recently after it had been mostly sitting for most of 4 years. Only now am I able to get to service it but have driven it on errands - 148 miles total. First partial fueling was at 83075, 3 more partials then a full tank at 84223 miles with a can of Techron. It threw P0174 & P0171 at 84215.

So total...
Miles driven - 143
Gallons used 26.153
Gas cost - $56.89

According to 2 MPG calcs that's only 5.7 mpg. Fuelio says 10.9 but still, quite atrocious!

I finally have some time to service &/or replace the usual suspects.

-Air & Air Filter
-Spark Plugs/ plug wires
-Throttle Body / MAF / IAC Cleaning
-Check if fuel pump is weak?
-Clean egr valve
-Clean egr valve
-Injectors cleaning - for now techhron into a full tank
-Replace O2 sensors???
-Smoke check for air leaks in hose
-Brakes dragging (but I don't think so)
-Flush coolant, other fluids
-Check failed fan clutch
-Test engine compression
-Check restricted exhaust/CATs

Anything else or tips?

Not looking for great gas mileage but but normal 14 -18ish mpg range.

 

[Dirtman]

Is it blowing black smoke and reeking of fuel?

 

[Jay11]

Negative on both

 

[fastpakr]

Your numbers don't make sense.

The fuel used to fill it up at the first gas station isn't relevant. The only thing that matters is getting it completely full and resetting the odometer.

Assuming it was -full- when you left the first gas station, how much did you put in at the second stop after 143 miles?

 

[19Walt93]

Check the O2 connectors and grounds for corrosion, sitting for 4 years isn't a good thing. Lean or rich codes like P0171 and 174 aren't a diagnosis, they're symptoms. Also the truck is a Supercab, Ford never built an extended cab.

 

[Dirtman]

Negative on both

Then you can't be getting 5.7 mpg. The engine literally can't burn that much fuel... it would be dumping out of the exhaust and smelling like a fuel tanker.

 

[Curious Hound]

Then you can't be getting 5.7 mpg. The engine literally can't burn that much fuel... it would be dumping out of the exhaust and smelling like a fuel tanker.

Maybe the parking brake is on, the tires are flat and he only drives up-hill.

 

[Dirtman]

On a serious note. If you have a scanner. Bring up live data for o2 sensors bank 1 and bank 2 sensor 1. Make sure they are switching properly. They should bounce from 0-.9 volts constantly. If not they are not, they aren't working. Then bring up long term fuel trim. What is it at idle, and then mash the gas and put load on the engine? Its obviously high to get lean bank 1 and 2 but if it drops like a brick when the motor is under load, you have a gross vacuum leak. Then run a battery of vacuum tests. Steady, throttle blip, steady high rpm. You can tell alot from a vacuum gauge. Then finally fuel pressure test. Next would be test maf sensor flow rate. You said you cleaned it but what is the gps reading at idle?

 

[Jay11]

I did 34 miles after the previous, first full tank. I refiled the tank and the app worked out to 12 mpg-last photo.
Had an abrupt trip, so I haven't had a chance to check or do anything from my list.

@ericbphoto - Thanx for the chuckles, really made my day!


Used TorquePro, here are screenshots. I am trying to learn what all this means. But if you guys can offer your insights I would appreciate.

I drove around to let it warm to operating temp. Before driving off idle was not smooth. In fact engine stalled immediately after engaging reverse. It almost stalled at the first stop light, had to give it a little gas. I no longer have any codes (I had cleared the p0174+p0171 after previous full tank with techron cleaner), driven 34 miles, and no CEL has appeared. Anyway here are pics @ idle after returning


I noticed o2 sensor 2 was constant @1.27v. The others were bouncing between 0.54v, 0.49v, 0.73v.

Also noticed total number of misfire - 38. What does that mean?

Here are pics @2500 rpm. I did mash gas and I think I saw LTFT drop to a 4.26 then climb back to 21%ish.

12mpg per Fuelio

 

[Dirtman]

The downstream sensors should not switch the way the upstream sensors do. If they do that means your cats have failed. Ignore the misfire monitor.

You're fuel trims are extremely bad and the CEL will return soon.

 

[Jay11]

Ok. So cats replacement is on the agenda. What else would you do to redress these issues or pretty much my OP covers that?

What is the risk of driving with bad cats if I don't get them changed right away but later if I first address these other issues then cats later?

 

[Dirtman]

Why do you think your cats are bad?

 

[Jay11]

Did a compression test, following cylinders bank arrangement.
Cylinder 1-170, 2->160, 3->175, 4->175, 5->172 6->170
P/S First test on cylinder 2 was 165. Something made me re-do it twice, it came to 160 twice.

Do these numbers indicate or point towards anything? Or what would you do next based on these numbers? When I pulled the compression tester outta 2 and 3 it had a bit of oil on threads.

Should I do a wet test as well (I learned later there's a dry & wet test.)

No store around here has a leak down test kit rental so I will have to make one soon.

When I removed spark plugs I noticed white soot??? on 2&3 on the tip that makes contact with plug wire. What does this indicate?
The rest of the plugs are as below, is their condition indicative of anything of concern?

PCV
I have been trying to Google it's location without success. I don't seem to have the pipe from leftward of throttle that's known to crack on the 90 degree rubber hose (marked in red.) Where's the PCV valve location on this truck?

 

[Dirtman]

Pcv valve is on the drivers side valve cover towards the rear.

 

[Jay11]

Thanx Found it-EZ to replace but what a nondescript lil piece of &#!$@! No wonder I kept missing it.