A real puzzler, where did I go wrong? | Ford Explorer Forums - Serious Explorations

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A real puzzler, where did I go wrong?

SoHK_alumni

Well-Known Member
Joined
July 29, 2014
Messages
462
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12
City, State
Tampa, FL
Year, Model & Trim Level
5.0 V8 2002 Ranger
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
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:

20141011_183010_zpsz3qkjjvj.jpg
 



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Think I'm going to pull the timing cover and verify the cam timing.

After that, shoot, I might just build another 5.0 for it.
 






Got the timing cover off, found the cam correctly timed (no real shocker but it was worth the look).

But...Saw that the CPS timing had drifted. Found the pin for the can synconizer driven gear had shattered. Only a small tip was still driving the syncro.

OMG! Stupid close to loosing the oil pump drive! Even if today's effort does nothing for my fuel economy, I'm very glad I found and repaired the syncronizer problem.

Replaced the pin, timed the CPS to the still TDC cam/crank and reassembled. Found the new harmonic was 5º off. Warantee claim here I come.

With the CPS timed FOR SURE to TDC for the 1st time since building the engine, maybe, just maybe I'll see a change on behavior.
 






I can't offer any help as you're far over my head, but I just wanted to say great "Ranger V8" emblem on the engine! I'm assuming you fabbed it?
 






I can't offer any help as you're far over my head, but I just wanted to say great "Ranger V8" emblem on the engine! I'm assuming you fabbed it?

Man I wish I had those skills! (and equipment). Found that mostly by accident over on TRS during my education phase of the V8 project. A guy there had a small run of them made and I liked the idea.

The crashed Explorer I'd bought had the "Explorer V8" intake plate and I knew that was going into the scrap bin.

Since I was not building a HO engine, I thought going to the HO plate would have been pretentious so had started looking for a later Explorer "5.0 V8" plate.

When I found the Ranger V8 plate, I had to give in to a bit of vanity!

Besides, I was going for as OEM a look as possible. Since Ford put an "Explorer V8" intake plate on the Expo's, why should they not have used a "Ranger V8" one if they'd built the Rangers that way?
 






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.
 






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.
 






If the O2's are showing proper ratio... then you get what you get. It is running correctly and getting the right mix. I think you are on track:

"Still, push comes to shove, I think I'm fighting an efficiency problem, not a fuel management problem."

What rpms are you turning at 30 & 60 mph? You might just be turning too many rpms, and you have to provide fuel for those rpms whether you need the power developed or not. The numbers for 30, and more particularly 60 will tell. If you are turning over 2k @ 60, that's a bit much to expect good mpg. A V-8 should be loafing closer to 1000-1500, IMO. The 3.8 V-6 in my spouse T-bird is barely over 1200 @60-ish speeds. Standard size tires.
Have you checked that the odometer is correct, or measured and made corrections to your mpg calculations?
tom
 






What fuel system are you using? Did you swap to a return setup? The 96 pcm uses a return setup and everything 99+ is returnless and run much higher pressures.
 






What fuel system are you using? Did you swap to a return setup? The 96 pcm uses a return setup and everything 99+ is returnless and run much higher pressures.

Fuel system has the high pressure regulator in the tank removed and a return added beteween the engine's fuel rail and the original fuel return on the Ranger. Symptoms have persisted using two different fuel pressure regulators.


What rpms are you turning at 30 & 60 mph? You might just be turning too many rpms, and you have to provide fuel for those rpms whether you need the power developed or not. The numbers for 30, and more particularly 60 will tell. If you are turning over 2k @ 60, that's a bit much to expect good mpg. A V-8 should be loafing closer to 1000-1500, IMO. The 3.8 V-6 in my spouse T-bird is barely over 1200 @60-ish speeds. Standard size tires.
Have you checked that the odometer is correct, or measured and made corrections to your mpg calculations?
tom

Yes, speedometer and odometer are accurate to within 1.5 mph at 70 -- certainly close enought to not be a player.

In 3rd gear, the engine is at 1400 rpm at 30 mph, in 4th with the torque converter locked up it's at 1800 at 60 mph.

The Ranger is what? 700 lbs lighter than an AWD 5.0 Explorer? yea, I'm running slightly smaller tires (225/70 15 vs 235/75 15) but the rise in ratio from 3.73:1 of the Expo to the 3.27:1 in the rebuilt Expo rear end still leaves me with a bit higher ratio than the Expo had originally.

Commonly in the V8 Ranger circles, guys are routinely getting mid 20's on the highway and high teens normal commute. I should be getting at least what an Explorer would get yet my BEST highway milage is pure in-town milage for a V8 Expo. Something is definately out of whack.
 






fuel trims?

. . . 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. . . .
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. . .

What do you mean by "very high long term fuel trim and very low short term fuel trim"? Do you mean they are both positive but the LTFT is say 20% and the STFT is 0%? Or do you mean the LTFT is positive and the STFT is negative?
 






At no load idle, long term fuel trim on bank 2 goes to 20% or so and short term trim same bank goes to -15 to -17%.

As soon as its taken out of park or neutral, trims revert back to near 0%.
 






lean condition at throttle release?

As I recall the LTFT will not change when the engine is idling. I suspect a lean condition is occurring when you decelerate and the PCM richens the AFR to compensate. Then at idle since the PCM does not change the LTFT it has to lean the AFR by changing the STFT. Does the STFT cycle when the engine is idling? If not, check to see if the PCM is staying in closed loop. Are you using the 1996 PCM?

I suggest that you monitor the Throttle Position Relative Closed Throttle pid with the engine off/ignition on. It should vary smoothly from 0 at closed throttle to about 755 at WOT.
 






Yes, both PCM's are from '96's. And yes, once the engine warms up enough to go into closed loop, it stays there.

Having trouble finding a tool that will display relative throttle position. The absolute readings I get is a very smooth swing from 15% to 95%. Going to try Forscan with my ELM327 to see if it can display the relative position.

The other PID I can't seem to display is the misfire count. As strong as the miss is at times, I'd like to see if the miss continues into the higher RPM range or if the miss is in a specific RPM range.
 












On the 96, EGR is integral with the intake. Initial startup gave a couple EGR faults. Cleaning the valve and replacing the EGR position sensor resolved the faults. Not seen any excessive or inadequate EGR flow faults since.

Think I'll dig out the old Simpson multimeter. Should be able to prove the TPS.
 






Equal EGR flow to both banks?

Is the EGR configured so there is an equal flow to both banks?
Is there an easy way to disable the EGR flow to see if that has any effect on the miss and the fuel trims?

The PCM computes the relative power pulse of each cylinder. If one cylinder outputs significantly less than the others then the PCM sets a misfire DTC. Since you have no misfire DTCs the low power between 1500 & 1800 rpm is probably fairly uniform. The most likely cause of misfire is ignition. You've tried different coilpacks and different spark plugs wires. As I recall some Torque Monster users have experienced clearance issues between the spark plug and the header. You might try observing the spark plug wires in the dark to look for arcing.

You have a waste spark ignition system. Spark plugs are paired with one firing on the compression stroke while its pair fires at the same time on the exhaust stroke. This allows the use of only 4 coils instead of 8. Current flows thru the plug in opposite directions in Bank 1 than in Bank 2. You posted that you have single platinum plugs. I suggest dual platinum or dual iridium plugs in waste spark ignition systems. Also, what brand of plugs are installed? Some forum members have experienced problems with Bosch plugs.
 






The EGR system injects exhaust gasses very early in the intake stream, shortly after the throttle body, well before the intake plenum separates into individual separate runners for each cylinder.

On the upside, should be very easy to block off the vacuum line either going to the EGR solenoid or the EGR valve itself. (have a golf tee ready for the job!)

I've tried two different sets of ignition wires, both sets wore insulated heat boots over the ends to protect them from the TM headers.

First set of plugs were NGK platinums, current set are Motorcraft coppers. Engine behaves the same with either set but for long term use, I agree, the double plat's or iridiums are the way to go.

It's the wasted spark system that allowed me to turn the two coil packs 90° and re-index the wires pair for pair so all the wires at the front of the coil packs head over to one side of the engine and the back set of wires to the other. (a bit of vanity on my part) I kept each pair of coil towers associated with their pair of cylinders, but swapped a couple front to rear for the desired effect. Moving the coils is a very recent effort, had ran both the oem and Accel coils in the original orientation.

You've confirmed my understanding of the misfire detection, gives a very strong indication that what ever is going on, is going on across all 8 cylinders at the same time. -- Screams timing! timing! timing! yet I've done all I can to verify all the timing components. Have a fresh crankshaft position sensor ordered since it's just about the only component that is original and related to timing. (other than the camshaft that I never even thought to verify the part number of)

Won't deny it, I'm getting really (really!) close to building a different 5.0 for the thing. Hmmm, Bit more aggressive cam, Dart heads, get it tuned to match and have even more fun!

After I get the new crank position sensor in, I'll get the Ranger onto a dyno. Really want to see how the engine performs -- I'd gone from a 175K mile 3.0 to the fresh 5.0 so I really cannot judge expected performance to actual. A dyno won't lie and if the performance numbers are out of line with a mostly stock 5.0, I'll learn something.
 






At least some progress

After two failed attempts to check fuel pressures, a trip to the local hydraulic hose shop got a working solution.

At idle, fuel pressure is 29psi with 24" of vacuum on the FPR, 38 psi w/o vacuum. Def on the low side of spec.

Also noted my rail pressure faded much faster than expected.

Since the FPR and injectors have already been replaced, decided to add an in-line check valve before the fuel filter.

The result? Seems my hot start/restart is cured! Yea!

I've ordered an adjustable FPR, will set it at the high end of spec on install.

Also have new Crank Position Sensor due in.

Will get both in as soon as possible.

Its just about time to start shopping for a decent 5.0. Do have a couple Q's -- Do the GT40P heads support the through the intake EGR system? My TM headers don't have the external EGR port but its much easier to find late Expo GT40P 5.0's around my area than the earlier GT40 5.0s. Or would it be worth my time to find a forged internals 'Stang 5.0 and find a set of GT40 heads for that?

If I go a replacement engine path, I'll buy and install used then go through the current 5.0 to ID the problem. Find and fix what ever is wrong inside then swap it back in.
 



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