2.3L ('83-'97) OBD1 Code 56 MAF- SOLVED!!!!!! Yeah!

[corerftech]

1990 dual plug. Disaster from Bubba. Electrical nightmare!

Today made huge advancements on repairs, all of which were caused by several nipple heads who touched it before me.

Prior I had code 18 short, 56 MAFv too high and something else related to ignition (coil 3 dead code), tach was dead too.
Installed Standard ICM (new) and voila- tach alive.

I had to tear things apart to get to I inspected possible faults. Opened timing belt cover, verified cam timing. Removed both coils, DVM tested, found primary (exh) cooked on one bank with very high secondary and primary. Replaced with a real motorcraft from a 5.0 I had, replaced the failed radio filter cap as well. Failure found to be from the cracked and broken heat shield below. I welded it back together and reinstalled the coil and filter. All connections are sterile clean as well and all wiring faults (short/rub/fray, etc corrected).
Intake coil is aftermarket as found and tested at 13k13k, 0.8/0.8 ohms so I reinstalled after cleaning. Tested its filter cap, no issue, 25uF. R&R all intake side plugs. Prior all exh side plugs were found hand tight. Simply R&R and gap them from .090 as found to .044 actually caused the engine to run! This time I cleaned the best 4 plugs with grit cleaner, gapped to 44, installed on intake.
New Delco copper gapped at 44 installed on exh side. All plug wires dressed and installed in correct locations.

Sterile cleaned the intake manifold at ICM and degreased sterile all 3 ICM screws. Installed with sink paste the new Standard T series ICM and torqued to 28 in/lb. Ground quality is excellent for the ICM, old one has loose screws and no sink paste( was an aftermarket, probably fried drivers inside).

Finally I fired up the engine and it ran, with tach functioning (calibration is off due to me messing with adjustments in dash prior trying to make it work, I’ll tear IP out again and adjust for proper RPm).

With timing light verified NO spout, 10BTDC and with spout, about 18BTDC at idle.

Fast idle calms down as it should after start. It’s definitely rich still. I didn’t mention that the intake plugs were spraying fuel everywhere they were so loose. Plus the coil pack didn’t work due to ICM fail so they were damn near shorted with rich fouling.

So after clearing codes and a static test run in garage, I have but one code, 56, MAF voltage over/out of range/excess.
It is an aftermarket MAF (not mine), I did clean it but made no difference (with MAF cleaner). It has blue elements on sensor itself and wires are undamaged.

The running issues (in garage):

Code 56
Off idle if you really slowly climb into the throttle, it will rev past a bumble at maybe 1500-1660 rpm.
If you stop at 1500, it will sit and sputter.
If you punch it from idle, perfection.

Like an idle transition jet issue on a carb where the mains take over and improper jetting.

So I’m no wiz but if MAF V is too high ( granted it may be a bad sensor) then ECU says add fuel to compensate for huge airflow, which would cause a rich condition period.

I don’t know how to look at this issue. Can the MAF sensor cause this type of over rich??

Also are aftermarket MAF sensors worth a damn? If I buy one, likelihood of a bad/ piece of crap from the aftermarket company???

Lastly if it has been running Uber rich for a long time, it’s there a potential for an O2 sensor concern??

No CEL anymore either, and not because the bulb burned out (which was how I found the truck- LOL)

Other than it running rich, a code 56 and the stumble the engine is ready to rock and roll.

long post , needed to ensure some history was present for discernment.
Any input would be appreciated.

BTW: opened ECU, inspected what looked like a 3.3uF/63v and another “can’t remember value” at 63v radial electrolytic on board. No bulge, no leak, conformal coating perfect. I’ll still replace them but…… I don’t think they are currently causing issues.


Mike in Memphis

 

[corerftech]

I debugged the MAF circuit.
line C on the connector is the ECU provided ground.

While disconnected my ground (line C) in Key On/Eng Off, 5.5vdc roughly, should be Battery B+ value.
in circuit it pulls waaaaay up so the signal line, Line D, is zooty at like 10v. Hence my code- 56, MAF sensor voltage HIGH out of range.

All other terminals test as they should, A/B/D and with ECU disconnected, pin 46 (tan w blue tracer) which is Line C on the MAF, loop resistance is 0.4 ohms. So the harness has no fault (but I know that all lines a-d were rubbed by metal and shorted at some point in the life of the car (thanks again Bubba from MS!).

Ultimately the ECU sense resistor is smoked, wherever it is.

Basic trace following from pin 46 inbound shows an SMT cap, then a Via, top of board termination into pin 6 of a resistor network (ford part F07F-AA 8948, see picture attached).

Anybody know what resistor would typically fry for the MAF input line??

nothing visible, it’s out of spec, not flamed out.

Best place to buy a reman computer from??? Looking for a recommendation.
Thanks in advance!

 

[corerftech]

Well thought I lucked out on R109, cold/cracked solder joint. Reflowed it, after verifying it WAS part of the path of pin 46. Resistance in circuit changed about 1.5k (actually the value of the resistor).

fired it back up. No help.

Tested the MAF connector again, A 12V, B GND (0.5ohms loop to battery terminal), C (key on) Friggen 5.7v to Positive batt terminal, D (while running at idle: .890v or so which got me excited but then I realized- crap, C is still limping with a horrible ECU ground path.
Tested several nodes of the vehicle (ground), chassis, cab, etc—- all under 0.5 ohms to the battery cable. My leads are 0.2 of that so the ground is low impedance everywhere.

ordered a Cardone replacement from RA/////

I believe I have fought through all testing to prove the MAF ECU ground is the fault of my code 56.

Interesting, I have no idea of what R109 does but my tach was a bit jumpy prior to reflow and now is as solid as an auto meter.
Coincidence???
Saga continues.

 

[corerftech]

Alright, updates to the situation.

RockAuto delivered a Cardone ECU on Saturday and I promptly installed and tested this evening. Before initiating a run test, I installed, added battery power, tested the MAF GROUND (pin C) with ignition on, found 6.0v to positive battery post. So I still dont have 12V per the diagnostic methods I have found online for Early Ford MAF 4 wire system.

After failing that test, what the hell, Ill start the car. My TACH crapped out instantly bouncing like a ping pong ball.
Truck ran much worse than the old ECU.
Still coded 56, MAF over voltage.

For fun, I removed the MAF body completely so WIRED but NO AIRFLOW.
I for the few seconds the truck would run with NEW ECU, It coded 66, thats a MAF UNDERVOLT!
So the MAF is sending some info to ECU.

I reinstalled the OLD ECU, solder repaired on a cracked resistor. The truck ran like a champ (as well as before), TACH STABLE AS A ROCK.
Coded 56 only.

I am returning the NEW ECU legitimately as the TACH, on 3 separate installed attempts, fails to operate with it. I believe it has more issues than my OLD ECU, my OLD ECU may have ZERO issues now that the cracked solder joint has been reflowed.



I tested the "bridge" on the MAF with a VOM. The MAF works like a load cell, having a Wheatstone Bridge with an imbalanced leg that is thermally changed in value. So I found significant imbalance on the static legs (about 330 ohms but varying 5-10 ohms) and one leg is at 556k ohms!! In my world of strain gages, "we" hold a good gage at less than 1 ohm imbalance and arguably less than 0.2 ohms DCR with no strain applied. Now the MAF may be far less critical as we measure MICROVOLTS in imbalance for outputs and the MAF is a range of 0-5VDC....... maybe 10 ohms is no big deal. BUT!!!!!!! 556k is WAAAAAAY wrong.

I cant see whats inside the plastic case so this test was both from one external terminal and the 4 welded posts that support the gage elements. Also got the same measurements just measuring between the welded posts.

Its obvious the ECU is not the problem. I again, for the third time, tested the MAF ground (actually PIN 15, I misposted pin 46 prior) and its 4 feet long from header connector to MAF connector. It is isolated, insulated with no conductivity to any other point in the truck. It has arguably ZERO DCR.

I ordered a DELPHI brand MAF sensor on Amazon, actually has a part number!!! Crossed it to several references so its the correct MAF for a
'90 2.3L engine.

I intend to measure the bridge before installing the new MAF to get an idea of what a GOOD MAF tests like.
Ill report what I find for others to reference.

I am hoping the jackhole who owned the truck prior who put a part numberless item in as the MAF, killed the MAF and/or installed a POS junk device.


I will add this:

JAckhole installed some "COLD AIR" Specter/Spectra/Sped Junk Crap (actually a HOT AIR system from what I see) with a K&N cone filter.
The 4 inch ALUM tubing is OK, no leaks. Its JUNK but serviceable. I dont have a donor to get OEM parts back for it.

I have but TWO concerns with this:
K&N Oil will foul the new SENSOR.
Would there be any issue with it flowing TOO MUCH AIR into the MAF???

I.e., Like removing an air cleaner from an OEM system, is it possible to have TOO MUCH FLOW in front of the MAF due to very low restriction air cleaner or the like??? It makes no sense to me to have such a situation........ but is it possible???

Any input would be appreciated.

 

[corerftech]

So I’m out of state working and heading back to TN this morn and I took a look at my local JY inventory by phone. Low and behold a 1991 2.3/manual showed up with a 10% off coupon!
Hell, I need to go try to get at least a windshield for my 87 and maybe, just maybe, an OEM MAF.

Holy sheep dip, the whole top end remained and more, plus it was ALL OEM.

I was able to pull the entire air handling system ,front clip funnel to the throttle body hose clamp, including bolts/nuts/heat riser, vac lines, etc. Unmolested unlike this MS car I have had to deal with.

What I failed to share was that MS Bubba Bonehead prior owner went to a local parts store and must have really liked the shiny spectra universal intake parts and a K&N AF (cone of course).

I have dreaded it since I started Thai ordeal.

I was able to (in 3 minutes!) lock in the OEM parts, replace a suspect vacuum line set (R/G/B for AC and Fuel Pres REG) for giggles just because it was cleaner and in better overall condition than mine.

I ran the car till normal idle, off, cleared all codes, Restart and idle down. It now idles at what I think is about 600 (tach needs recalibration from attempted repairs), the crap spot at 1600 rpm on slow throttle advance is gone, engine runs like my 2011 120k mile old car. It behaves perfectly. A few taps on the throttle (WOT) would have set code 56 prior. OMg, no codes!!!

See the attached pic of the aluminum crap vs the mocked in OE parts. The Spectra was running a full 4 inch pipe with reducers at both ends.
There is mo computer failure, no QUAD driver failure, obviously the internet diagnostic procedure of Batt B+ voltage on line C of MAF (Line C is ECU switched ground) is Bu//spit——- simply put the MAF from Mainland China that is unmarked is a POS and the Aftermarket crap is just that, POS Crap.

I get to return my replacement MAF that I ordered and it hasn’t even arrived. I spent $80.00 in JY credit and cash today (50/50) and it has transformed the truck.
I even got a bucket full of free screws, charcoal can caps and fittings, got to see what the OE config was, my coil mount screws were rusted at the sheet metal line and not gripping. This JY car got me fresh screws, man what a blessing.

I was contemplating taking apart the MAF and metering for a reference for people but I’m not touching the MAF. It’s happy——- let it live!

It has been an excellent learning opportunity- truly. Frustrating as it cost $$ to fix more than desired but…… I know so much more about the EFI system (I knew nothing!) and have a loose grip on Fords EEC4 system, wiring, demands, failure modes, etc. That is worth the price of admission.

 

[scotts90ranger]

Holy cow, you are much past the average poster

It's a simple system unless some jackwagon screwed something up then unloads it on someone unsuspecting... I'm glad you figured it out and posed up the prognosis, should hopefully help for the future.

 

[RobbieD]

Good job! And I have to applaud your perseverance, sir.

"Stock rocks!"

Thanks for the detailed write-up.

 

[bobbywalter]

You should edit probsts book....and revise it for 2022

 

[RonD]

Just for those that read this the Mass Air Flow(MAF) sensor doesn't actually read the "flow" of the air
MAF sensor reads the density and temperature of the air, and it only samples about 10-15%

The computer is already programmed for the "flow" of air that can come into, in this case, a 2.3 liter engine, that's just math
2.3 liters of air can come in at Wide Open Throttle(WOT) every 2 RPM(full cycle of 4 stroke engine), less air at lower than WOT, just math

The MAF, in essence, weighs the incoming air
14.7:1 air:fuel ratio for gasoline is a WEIGHT RATIO
14.7 pounds of air to 1 pound of gasoline
14.7 grams of air to 1 gram of gasoline

And the weight of air changes quite a bit, at sea level on a cold day the air is way heavier than at 5,000ft elevation on a warm day
The MAF is there to weigh the air, so computer can add the correct weight of gasoline
But MAF only samples 10-15% of the air so a small error at the MAF can change to a big error(times 10) at the computer's calculation
Which is why a "dirty MAF" can cause running issues


No, oiled air filter should not cause any issues with MAF system, although some are too small so can restrict air flow at WOT, if you can "hear" an air filter its restricting air flow

MAF sensor is matched to the opening it sits in, that's the 10-15% thing that the computer "knows", is programmed for
Changing to a larger throated MAF can be OK...if the sensor is also larger so its reading the same % of air that the computer expects

 

[bobbywalter]

That is book, sound theory ... but remember Changing any part of the tubing can alter reading...even just being loose.

You can usually hear an open filter like a oiled k&n.. It is not a restriction necessarily. But it can contaminate maf ..and often do when over oiled, it is a common issue.. Depending on installation they can alter maf data. Very observable .