I have a 1996 Explorer 5.0 tucked into the nose of my 2002 Ranger. Went through the 5.0 before installing but had to have missed something. Getting very poor fuel economy and I can't figure out why.

Hoping a fresh set of eyes and minds might turn up an idea or two cause I'm surely out of ideas and know I've missed something somewhere.

Symptoms:
13.5 – 14.0 mpg average fuel economy over 3K miles
Noticable miss, particularly at 35/40 mph – 1500/1800 rpm but idles smoothly at 700 rpm
Perfect cold but poor/long/stumbling hot starts. (inline fuel check valve seems to have resolved the hot start issue)
No CEL/Fault codes
Torque reports 17 – 19 mpg average yet no hint of a fuel leak
Fuel economy same driven gently , or enthusiastically.
No change to engine behavior when CPS taken out of time.

Test data:
130 – 135 psi dry/cold compression across all 8 cylinders (perhaps a bit low?)
Both short and long term fuel trims hover around 0%
Engine temp sensor reports 195° – 205°
Idles w/23” vacuum
Correctly toggles between open and closed loop fuel management
Speedometer accurate to within 1.5 mph at 70. (vss vs gps)
0 PSI exhaust back pressure at front 02 ports at 50 mph.

Specifics:
02 Ranger w/’96 Explorer 5.0, 4R70W box, rebuild Ford 8.8 TracLoc w/3.27 gears, TM headers, original Cats, 3” exhaust after cats. Stock cam, pistons, GT40 heads.
145K mile engine refreshed with rings, bearings, valve springs, t-stat, pcv etc. Block, cam and crank mic'd well within spec.
New plugs, air filter, front O2 sensors
Std copper and platinum plugs are clean, gapped to .054” – still look new
2 sets ignition wires
Original and “rebuilt” set of fuel injectors
Original and replacement FPR
Original and Accel ignition coil packs.
Original and replacement CPS, timed with OTC alignment tool while timing cover off the engine
Original and replacement Crank Position Sensor
Original MAF, TPS and IAC
Found harmonic balancer was 10° off, replaced with new, no change (of course found the new is 5° off!)
Original and replacement PCM.
Very strong spark at all 8 coil towers.
Verified fuel pressures, both with and without vacuum to the FPR.

The offending lump:

Do you know what the fuel pressure is at 1500 rpm?

I noticed with mine torque app mileage reading is a lot higher than my figures I from my odometer even with both showing the same traveled distance. The app shows an average of 30-32 and on the odometer I get 23-25.

By the way, that looks nice.

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2014 F150 xl 3.7 6 speed auto.

Good to know that Torque might have a fuel econ calc issue. At first, I was hoping/thinking to find a fuel leak but no odor or wet spots backed up that idea.

I've not given fuel pressure a lot of consideration. The original FPR had some physical damage but the symptoms remained when I changed it. Add in the very low fuel trims, both long and short term and I've just taken fuel pressure on faith (along with the MAF). Will look to see if I can piece together an adapter to be able to install a gauge I can check while going down the road.

Thanks for the complement on the engine. I tried to keep it from looking hacked up, or blinged up. Was sort of going for the "hey, I didn't know Ford put a V-8 in the Rangers" look.

Thinking I might be able to mod/adapt a semi's tire pressure equalizer to get a gauge onto the fuel system.

Went out this am and picked up some gaskets, going to pull the timing cover and verify the cam timing. Had double checked and used a 2nd pair of eyes but I'm so out of ideas I think its about the next step.

Won't deny it, I'm getting close to building another 5.0 for it.

23 inches on the vacuum gauge is a bit high, you could have a timing issue. http://www.international-auto.com/fi...uum-gauges.cfm

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2014 F150 xl 3.7 6 speed auto.

Yep, the higher than expected vacuum and lower dry/cold compression were the reason I decided to pull the timing cover.

Found what looked like proper cam timing



So verified it



Went to double check the CPS timing and it had drifted. Dug into the syncronizer and found a broken pin for the driven gear. Can't say its THE problem but certainly is a problem.



Replaced the pin, re-timed the syncro/CPS



Just gotta get it back together and see.

Good thing you dug into it and found that bad pin before it totally failed though.

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2014 F150 xl 3.7 6 speed auto.

No kidding! Just one small bit of that broken pin was all that kept the oil pump going. Stupid close to loosing the whole thing.

Even if today's effort does nothing for the fuel ecenomy puzzle, I'm super glad I made the effort.

On a further note, I left the cam & crank at TDC for assembly -- my new harmonic ballancer is marked 5° off. So now, maybe, I've got a correctly timed CPS!

More fun with the 5.0 after reassembly -- The used Explorer radiator had a couple globs of epoxy on it and I must have disturbed one during the day.

Got the cooling system refilled, started the engine and quickly found coolant going every where.

Mad scramble to find a '96 Explorer 5.0 radiator at 7:00 pm on a Sunday evening and then get it installed. Grrrrrrr

Gotta love the information age though, found the rad only about 15 min away. $190 out the door with a gallon of fresh coolant. Yea, Rockauto would have saved me a ton of cash, but the Ranger would have been parked for days waiting on it.

Next phase is probably to trace all the wiring in the engine harness, or perhaps simply to pull the harness and replace it with one from a breakers yard. There's GOTTA be a root cause that I'm not finding. I can eliminate some of the wiring since I don't have any CEL's but there's a problem.

Does anyone know if there's a knock sensor on these things? Can't say I remember one when I tore down the engine and built it back out.

Look at the back of the engine were the bell housing bolts, that is the area only I've found searching but it's on the older 5.0s. Also look around the intake.

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2014 F150 xl 3.7 6 speed auto.

Hmmm, found a rather odd behavior/symptom yesterday.

Been messing around with the Torque app, trying to make it easier to monitor the goings on in the PCM and engine.

Only at idle (Park or neutral), only while fully up to temp, bank 2 goes very high long term fuel trim and very low short term fuel trim at the same time.

Say what????

Swapped in a spare, used O2 sensor, same behavior.

Reliable as clock work, easily repeatable.

Cruising down the interstate, all fuel trims are within a percent or two of 0. Come to a stop in gear, only minor changes. Put the transmission in park or neutral and the bank 2 trims take off in opposite directions.

I don't get it!

Since I don't spend much time under the specific conditions, I doubt it's the cause of the fuel economy issue but I think it might be a symptom the root cause.

Not sure if the behavior is load related, or perhaps electrical -- only obvious mechanical difference side to side is the 2 piece Torque Monster header on bank 2, but there's no sign of an exhaust leak

Getting tempted to buy an Android tablet just to make using Torque easier, the screen on my phone is small enough to limit the info I can safely watch.

Still, push comes to shove, I think I'm fighting an efficiency problem, not a fuel management problem. It's as if I'm not getting the power out of the fuel used so I use more fuel to get the power.

The miss, less than stellar compression and very high vacuum all appear to point to a timing or mechanical problem, particularly when the PCM(s) appear to be working within normal ranges.

I'd hoped to pull the cam sprocket when I had the timing cover off, wanted to see if there were any markings on the cam to verify it's OEM but I could not get the sprocket to budge. Crank sprocket moved without issue but not the cam and the one 3 jaw puller I have was too small to grab the thing. Hope I don't regret that. A non-std cam grind might explain a whole bunch of what I'm seeing.

Wonder if a run on a dyno would yield any useful information. If torque or HP are out of line with what I think I've got under the hood, might be good info to have. Not sure I trust Torque enough, nor am I sure I could keep things legal if I try the 1/8 or 1/4 mile runs with it.

A dyno might be very helpful, you will have another set of eyes on it to.

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2014 F150 xl 3.7 6 speed auto.

The long term fuel trim on mine goes to +19 @ Idle but short term is at 0. Does the short term fuel go way negative at idle? If so you're running rich at idle on that bank so you may have a fuel management issue.

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2014 F150 xl 3.7 6 speed auto.

Yes, only at no load idle. Bank 2 goes upwards of 20% long term but -15% short term fuel trims. Bank 1 stays within a percent or two of zero. Damn odd. Any load at all and the fuel trims all approach 0%.

Did not notice that untill I swapped out the PCM. Might go back to the origial to see if that symptom remains.

I dont know, only original players still in the game are the crank position sensor, MAF and wiring harness. Tempted to replace both sensors. Its only money after all! Even the harness could be swapped out.

Buying another 5.0 and dropping that in is rapidly approaching becomming a viable option.

Before you buy a new maf and crank sensor I'd try switching injectors from Bank 1 to bank 2. The MAF sensor wouldn't cause problems just on 1 side of the engine and I don't think the crank sensor would do that either. One sensor not to be forgotten about is the TPS, I did a drivability test with it disconnected and when I would get near 35-45 I got a very noticeable misfire whether I was wide open or just on it. Doing this didn't effect short term fuel trim, but long term went from 7-9 (TPS) to 10-13(no TPS). The only time long term fuel trim should hit 0 is at wide open throttle. What speed were you going on the interstate?



I noticed you said it's hard to start and stumbles when warm. When you shut the engine off then immediately try to restart it does it it fire right up.

For some reason I think you have a leaky injector

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2014 F150 xl 3.7 6 speed auto.