> MAF HIGH (P0103) followed by MAF Low (P0102)... is that how they "burnout"??

[fixizin]

I must say, things are running a lot more "sane" on MAF Low--except for the dying at idle half the time--lots o' HEEL-TOE practice.

IT ALL STARTED with a STALL seconds after (Florida) "Cold" Start--I possibly gave it some gas--had been driving a classic carbureted vehicle recently... the immediately attempted RE-start was dramatic--behaved like STUCK OPEN INJECTOR, belching white smoke, raw gasoline smell in the air...
<< Code was P0103 MAF stuck HIGH at this point...

... eventually hit on crank-with-WOT, followed by DISCO-nnect BATTery Neg lead, touch to POS lead to discharge ECU/PCM, and THAT is when code switched from MAF stuck-HI to MAF stuck-LO...

Code Reader stuck at like 0.6 Grams/Sec airflow regardless of RPM, which makes sense if MAF hosed LOW. Fuel Trims normal, mileage good...

Cleaned the puppy with special MAF Sensor spray about 6,000 miles back, air filter swapped at same time. Looks pristine to my untrained eye, no filth or obvious broken filament...

>>> SO RELIEVED I didn't have to replace an injector, which is quite involved on Ye Olde Vulcan, amirite??

ANYWAY... any "tricks" I'm missing, or... am I buying a new MAF Sensor????

Thanks in advance.

PS: what's with the not just Torx screws holding down MAF, but SECURITY Torx?... AYFKM? Are these high-theft items?... oddly, it seems to be about the same price with the whole tube-body unit as it is standalone... lulz...

 

[RonD]

Unplug MAF Connector, if its a 4 wire MAF test the outside 2 wires for battery voltage with Key ON, one should be 12v the other is the ground, these are for the HEATER inside the MAF
Then test the 2 outside connector on the MAF, with ohm meter, should be under 200ohms

So is the MAF still not changing its g/sec reading with engine running?

And whats the exact code

These are the 5 "basic codes" for MAF
P0100 Mass or Volume Air Flow Circuit Malfunction
P0101 Mass or Volume Air Flow Circuit Range/Performance Problem
P0102 Mass or Volume Air Flow Circuit Low Input
P0103 Mass or Volume Air Flow Circuit High Input
P0104 Mass or Volume Air Flow Circuit Intermittent

 

[fixizin]

Thanks much, that's exactly the kind of multi-meter diagnostics I was looking for. It is the flat 4-wire connector.

P0102 Mass or Volume Air Flow Circuit Low Input is the recurring code... have erased it many times. But INITIALLY, before I reset the ECU, it was the opposite, P0103... was thinking it might've behaved like a fuse or light bulb filament at end-of-life, i.e. burn bright and fuse into a hard-short, before burning all the way through into open-circuit. Will probe when the sun is up.

So I guess it's running mostly-OK by relying on the O2 sensors for injector pulse-width data?

 

[fixizin]

OK, MAF connector is actually a 6-pin flat type, but only the inner 4 are populated. Engine running, the outer pair of the harness was sourcing 7.5V (had to insert paper clips, so tiny and deep are the female plug recesses), which surprised me--expected to see either 5V "ECU logic level" voltage, or the full "chassis level" 12V... are these 2 lines both from the ECU, or...? Is 7.5V not enough to heat the all-important filament?

On the sensor side, the outer 2 pins measuring OPEN CIRCUIT, so voltage moot...

Just did a quick check during lunch break, will tear into it tomorrow, see if any breaks visible.

BOTTOM LINE: disconnecting MAF while engine running made zero change to performance.

 

[Dirtman]

PS: what's with the not just Torx screws holding down MAF, but SECURITY Torx?... AYFKM? Are these high-theft items?

They are not there for theft reasons. They are there because it's an extremely delicate (and expensive) sensor so Ford doesn't want people messing with it. If joe blow got in there and tried cleaning it with carb cleaner and a rag Ford would be stuck warrantying a ton of MAF sensors. Security bits help keep the idiots out.

It sounds to me like you have a bad ground, I would test ohms from the ground pin on the sensor plug to battery negative. If that tests fine I'd be inclined to believe the sensor is simply failing internally.

 

[RonD]

You have some corrosion somewhere on the 12volt heater wire or its Ground
Measure each wire to battery positive and negative to see which one is not able to do full voltage

Rangers did get 6 Wire MAFs, Ford added 2 outside wires are for the Air Temp Sensor

So does your harness have 4 or 6 wires, and does the MAF have 4 or 6 connections?

If 6 wires on harness then outside wires are for air temp sensor so 5v
Outside wires on 4 wire harness are the heater
Should be red and black wires for heater on 4 or 6 wire harness

The MAF sensor works by the air flowing past it COOLING the heated wire, so if voltage for heater is low then MAF reading wouldn't be correct, I think the lowest thats acceptable is 10.5volts for the heater
And MAF only reads 10-15% of the air flow, so even a little off is a TIMES 10 mistake at the computer end of things, thats why dirty MAFs can cause issues, little error BIG mistake, lol

 

[fixizin]

So does your harness have 4 or 6 wires, and does the MAF have 4 or 6 connections?

Connector has 6 PLACES, outermost 2 UNwired, so 4 wires total... likewise the sensor has 4 metal tab-pins, outermost 2 empty... appears to be a fairly splash-proof dust-proof design. Even after 21 years, everything shiny and pristine within the connector.

I forget, where IS the Incoming Air Temp (IAT?) sensor on this engine?... believe I saw that parameter in real-time on my code reader... had to grab some OT today, won't be able to dive in until tomorrow..

 

[Dirtman]

If its not on the MAF (like Ron said the 6 wire maf has the IAT built in, 4 wire does not) it could be part of the MAP if it has one, or a separate stand alone sensor somewhere on the intake tube, or upper manifold. There is also sometimes an AAT sensor (ambient air temperature) not to be confused with the IAT when reading live data on your scanner. The AAT can literally be anywhere but generally somewhere on the front grill. I'm not super familiar with the 3.0. I'm sure Ron knows exactly where the IAT is, what color the wires are, and the name and social security number of the guy who designed it.

 

[fixizin]

You're good men with good insights, but... you're just not used to the '99 Twin Cities "Franken-Ford"... e.g. there's 2 different fuel line couplers--I've got both, one upstream of fuel filter, the other kind downstream of fuel filter... such ad hoc "what's left in the bin" examples abound, from grille to rear bumper license plate lamps... "parts is parts!"... just ask Wendy's.

ANYWAY, no biggie, in MAF-land, it's NOT the OUTER 2 wires that supply the constant 12V... but, per convention, it's the Solid RED for +12V and Solid Black for GND... the yellow w/ blue-stripe and lt. blue w/red-stripe are the sensor wires... IOW, I should've paid closer attention... or spent more time on TRS.

Even with the correct pins ID'd, Heater is still OPEN CIRCUIT, i.e. burned-thru...

Luckily Autozone is having a nice deal for the whole assembly, won't have to dredge up my Torx Security Bit... which I KNOW I have... somewhere... in one of those 21-piece Made-in-Cheena $1.88 specials H/W stores used to run... lulz.

 

[Dirtman]

Do yourself a favor and get a Motorcraft or Hitachi MAF sensor. Pretty much any other parts store brand is chinese crap that's gonna fail in a year if it even works out of the box.

 

[fixizin]

Any idea who sells Hitachi?... cuz even @RockAuto the Motorcraft is BEND OVER 4x the price of (probably) ChiCom or (possibly) Mexican generics... and as little miles as I'm driving, I... might just have to make do.

OR... see if my Lexus Master Tech bro still has his Ford Dealer connection... hmmm...

 

[Dirtman]

Advanced had the Hitachi sensor for mine. (Was about 60 bucks and mine is the more complex 6 wire sensor). Amazon has them too.

And there is a very very good reason motorcraft parts cost 4 times as much. They are 100 times less likely to fall apart in your hand.

But motorcraft doesn't make all their own parts. So some stuff you can just buy the actual brand that manufactured the original motorcraft part. Like motorcraft spark plugs are made by autolite. Their MAF sensors are made by Hitachi. (At least I'm fairly sure they are) but either way Hitachi MAF sensors definitely work just as good as OEM.

 

[fixizin]

Dang, Advanced has ONLY sketchy ChiCom brands for my 4-wire deal, and Ama-ZHON McBezos has every brand BUT Hitachi for my beast...

... O'Reilly no better...

 

[RonD]

Wrecking yard Motorcraft MAF is better than new anything else, just clean it, these rarely fail so not a big gamble getting a used one

 

[fixizin]

Well, MINE failed... but, hey, 21 years... OTOH, only 79k miles... hmmm...


So what are those 4 small bolts that hold the MAF tube to the air filter hood... 7mm?