A real puzzler, where did I go wrong?

[SoHK_alumni]

Best I know, Ford moved from the 28 oz harmonic balancer to the 50 oz in the early 1980's. So, on a stock later 302/5.0, the Explorer balancer should work.

On the stroker kits, a 28 oz balancer is needed and there's only one I know of that works with the Expo FEAD and no, it's NOT cheap!

 

[SoHK_alumni]

Just about ready to throw in the towel

New Crank Position Sensor and adjustable FPR are in.

Set the fuel pressure a bit high at 45 psi w/o vacuum, drops to 35 with idle vacuum.

Engine does seem a bit livelier, long term fuel trims now running about -8%.

Otherwise, no change in behavior.

Found an 80K mile GT40P 5.0 out of a '97 for $250 -- think I'm going to execute on that and hope I can get my '96 EGR system to work off the later cylinder heads.

Gotta decide if I'm going to just drop the lump into the engine bay or if it gets a refresh before hand. Probably at least give it new seals and gaskets but it's tempting to end to end the thing and completely abandon the current 5.0.

 

[SoHK_alumni]

Before absolutely throwing in the towel, though I'd try a few more things:

New MAF and different TPS, no change.

Using Forscan, have poked around the PCM, only issues it picks up that neither Torque nor my Actron 9180 were a pair of codes, P1137 and P1157 -- both rear O2 sensors reading lean.

Hmmm, well, what the heck, a pair of new sensors is a heck of a lot less work and money than swapping out the engine.

Gotta make an order from Rockauto for the wife's ride anyway so will try that.

 

[2000StreetRod]

not the downstream sensor

P1137 Lack of Downstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1
P1157 Lack of Downstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 2

I doubt that replacing the downstream sensors will make a difference. I think the DTCs are saying that the PCM is unable to achieve the desired result while staying in the specified range. In other words the fuel trims never achieve a sensed rich condition when cycling between slightly rich and slightly lean in closed loop. Is your exhaust configuration on the Ranger similar to the stock Explorer configuration?

 

[SoHK_alumni]

Except for the Torque Monster headers, the exhaust system is the Expo's till after the rear cats. From there, I built a "Y" pipe that dumps into a 3" inlet/outlet muffler.

The current rear 02 sensors are the fronts off my 02 3.0 and seemed to be in acceptable condition functionally before the swap.

You're right, I doubt changing out the rear sensors will "fix" anything but part of me want's to dot every external I and cross every external T before I toss a 5.0 in the recycle bin.

Still at this point, I'm convinced I'm facing an internal mechanical problem. I cannot imagine any "gross" EFI issue that would persists with all I've done, at this point, only the IAC and the engine wiring harness remain -- oh, and the PCM's engine temp sensor.

 

[2000StreetRod]

low compression

The poor fuel economy may be mostly due to the low engine compression. I think the compression should be around 170 psi instead of your measured 130 to 135 psi. Is the miss you're detecting (but the PCM is not reporting) possibly just due to low power from low compression? Low compression is a mechanical problem but you have replaced the rings and valve springs. What is the condition of the lifters and push rods?

 

[SoHK_alumni]

I've been very suspicious of the compression test results since first doing the test.

Most likely suspect for me is that the rings never seated but with no measurable blow by, I'm second guessing that diagnosis -- still, it's the best fit of my issues.

Unless I've got an alien cam in the engine, a single, or even a couple lifters, cam lobes or other valve problems would not give me such even compression readings and such an "even" miss that the PCM does not see a problem.

Still, I'm going to condemn the current hardware and get another 5.0 for it.

If the issues vanish with the replacement engine, I'll go through the current 5.0 and at least ID for sure the problem.

 

[boominXplorer]

Do you have an SCT tuner on it by chance? I know I can disable my rear O2 sensors and EGR with mine to be able to rule those issues out. The rear o2s are different then front o2s in just about every Ford vehicle, I think that is one of your issues. You can also play with the timing to see if things get better or worse and verify by watching the 1st o2s on your torque app. I have deleted the EGR on my ranger and used the sct tuner to remove the CEL, mainly because my oil fill is right where the EGR valve should be. Many people frown upon deleting the EGR, I feel the engine runs cleaner and intake air temps stay cooler without it.

 

[SoHK_alumni]

I've though about an SCT pretty hard a couple times, not sure I can justify one though.

I know it's crazy, but one thing I'd love to change in the PCM is to get the embedded VIN to match the Ranger's. Pretty sure that's one thing the SCT won't change.

Once I've got the 5.0 running correctly and know I won't be swapping out PCM's again, I might rethink the SCT, might be fun to see just how much fuel economy I could squeeze out of it.

For now, shoot, I'll be ecstatic just eliminating the stutter in the darn thing.

But even now with the abysmal fuel economy, the Ranger is so much more pleasant to drive. The 3.0 was gutless and felt strained at most tasks. Even running poorly, the 5.0 makes driving effortless.

 

[Turdle]

Have you tried sticking a vacuum gauge on this yet? I am curious what the idle vacuum is please.

 

[SoHK_alumni]

Torque reports 22 to 23 inches of vacuum but I've no idea where it gets those numbers. Best of my knowledge, there's no MAP sensor to report that.

My mechanical vacuum gauge shows a steady 21" at idle, dropping to just under 20˝ and returning to 21" when the a/c compressor kicks in.

 

[Turdle]

That is good vacuum and would indicate no leaks behind the throttle body.

There might be un-metered air entering between the maf and throttle body to cause a lean condition. Maybe the intake tube is split in a hidden area? I know this sounds basic but you might want to double check it. Pull hard on it, try to straighten the elbow to check for a crack. I know it's a long shot.

 

[SoHK_alumni]

I've been over the tube pretty thoroughly, the '96 used a round air cleaner and filter box and I went to the later square type for ascetics. Tried to ensure I pulled a solid one from the yard. Symptoms remained the same with both.

I've believe I'm fightjng something mechanical, maybe a ring/cylinder bore issue or a valvetrian problem.

Pretty sure I've eliminated the PCM and EFI as culprits. Both poorly seated rings or poorly seated valves fit a majority of the symptoms. But to have a similar enough "leak" in all 8 cylinders to keep the misfire detection algorithums from catching a problem almost defies the odds.

Even if I have to do a post mortum, I will find the problem!

 

[Turdle]

just reaching here, but, did you use the maf attached to the square box or did you use a round filter maf on the square filter box?

 

[SoHK_alumni]

Pulled the MAF out of the '96 air box and used that on the later system. The '96 MAF and housing are dimensionally the same as the later ones, but since the early and late systems use a different part number for the MAF or the MAF sensor, I chose to retain the MAF matched to the '96 PCM.

 

[Turdle]

I can't help but wonder if the different filter upstream of the maf might make a difference. It's worth trying the round one.

 

[SoHK_alumni]

I've run both air box systems with identical symptoms.

Push comes to shove, the round filter should be a freer flowing filter but I don't think I'll push the limits of either filter.

 

[SoHK_alumni]

And so it begins anew!

85K miles, $400 out the door complete except for the left exhaust manifold that I won't use anyway.

The "plan" is a quick clean up, strip to a long block, leave the heads on check up and install -- NO idea what I'll do if the problem survives this!

With this, I'll have a complete 2nd pre PATS EFI system with FEAD and manifolds. Hmmm, the possibilities are endless!

 

[tmwalsh]

stoichiometric-air-fuel-ratio

I didn't follow closely, but just read this:
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.

That's too many to expect the mileage the other rangers are getting. Should be closer to 1k, somewhat over, to get the miles. I think you can do some math, and figure the volume of fuel/air consumed by a 5.0 running 1800 rpm. You are turning 900(intake strokes@1800 rom) X 302ci of air and 'perfect' 14.7:1 ratio. ~5 liters of air X 900 / 14.7 for fuel volume every minute
4500 liters of air (turned into kg)/ 14.7 ratio = some number of kg of gasoline... It doesn't work going by volume as gasoline is a lot more dense. If you burned natural gas, the ratio is 17.2:1, so you'd have 261 liters of natural gas... to 4500 liters of air.
Added:
from a web site:

Since 23.2 mass-percent of air is actually oxygen, we need : 3.99 * 100/23.2 = 17.2 kg air for every 1 kg of methane. So the stoichiometric air-fuel ratio of methane is 17.2.

14.7 kg of air for each 1 kg of gasoline. Gasoline is ~8#/gallon. 1lb == .454kg so we need 2.2 lb ... hmm that's not right as it would be 1/4 gallon per mile ... Ugh. My brain is tired.


read here:
http://www.brighthubengineering.com/machine-design/15235-the-stoichiometric-air-fuel-ratio/

 

[SoHK_alumni]

Hmmmm, I could use the MAF to measure the air ingested, the raw volume of the engine won't work since the engine runs under vacuum most of the time. But, even with that info, the actual efficiency of the fuel combustion plays a significant part in how much power is achieved from the fuel.

I've read of guys with 5.0 Explorers getting upwards of 25 mpg at highway speeds and with the 3.73 gear ratio, they're turning more like 2500 rpm at those speeds.

With 3.27 gearing, 2100 rpm, similar aerodynamics and at least 600 lbs less weight, I don't think similar mileage is an unreasonable expectation.

So to, there are guys with 5.0's in their Rangers that report low 20's in daily driving and high 20's on the highway using the 3.73 gears. I should be able to get close to those numbers.

I might be wrong, but I'm convinced I'm fighting a mechanical problem that is killing efficiency. I'm guessing it's a problem with the valve train -- maybe a cam the PCM does not know how to manage, might have made a mistake when I lapped the valves or jpossibly the initial incorrect cam position sensor timing caused valve damage. One thing is for sure, it's extraordinarily unlikely that the 2nd 5.0 will have the same problem as the current. If it does, the problem will have to lie with the wiring or manifolds, both of which are really, really unlikely.

On the upside, if the replacement 5.0 gives similar issues as the current, I'll have a full set of intake and exhaust manifolds along with the wiring to swap those in as well.