MAF questions (Milehigh can you help?)

suberboy · Post by **suberboy** » Sun Jan 19, 2003 7:03 pm

Hope I've put this in the right spot if not please move it.

I'm hoping some one out there has some good information for me on the MAF that is used in the 2.2 turbo legacy compared to the MAF used in the 1.8 impreza L.

I'm doing a motor swap and using the 2.2 ECU but don't have the original MAF so I would like to know if I can use the one already in my 1.8 impreza?
I only know that one is a 4 wire (1.8L) and the other is a 5 wire.

-Can a 4 wire be used in place of a 5 wire?

-Does anyone know if they have different reference voltages?

-Is the reference voltage 5v or 5.5v?

-If they have the same reference voltages why aren't they interchangable?

-If I need to get a new MAF should I get it from Subaru or is there a better place?

Thanks for the any help!!!

Noah

Post by **Legacy777** » Mon Jan 20, 2003 4:15 am

The only difference in MAF's through the years is between MT's & AT's.

They are different types of sensors.

The MT ones should be silver looking, and the AT ones should be black

vrg3 · Post by **vrg3** » Mon Jan 20, 2003 2:11 pm

I thought so too, but that's not always the case... At least some manual transmission Legacies had the same MAF sensor as the automatics.

Basically, all turbos and some manual N/As had the silver sensors (part 22680AA170 if my memory serves me), and the automatic N/As and some manual N/As had the black sensors (22680AA160). I think all the GC Imprezas had the same black sensors.

I'm not sure (I'll check on my car later today), but I think only 4 wires are used even on the silver one, at least on my car. The fifth may be for an air temperature sensor or something. I have no idea about the reference voltage, but I don't think there even exists a 5.5 volt source on the car; almost all sensors are 5-volt referenced, and the ADCs built into the ECU are 0-5v 12-bit converters.

The difference between the two sensors may be how much air flow they are capable of measuring. The physical difference is that the silver metal one consists of a hot wire and the black plastic one is based on a hot film. Hot wire is supposedly more sturdy than hot film; I think the 1999 Impreza 2.5RSs had issues with their hot film sensors so Subaru replaced them with hot wire sensors.

I do have a spare Legacy Turbo MAF somewhere around here... if you'd like it make me an offer. I'd love to see your conversion work!

Post by **Legacy777** » Mon Jan 20, 2003 3:43 pm

The first gen legacies were mainly what I was talking about, when I was talking about the silver & black sensors.

I believe after that, they all got the black ones.

vrg3 · Post by **vrg3** » Mon Jan 20, 2003 3:51 pm

I was speaking about the early Legacies too... I know of at least two '93 Legacy 5-speeds with the MAFs with the black plastic housing.

entirelyturbo · Post by **entirelyturbo** » Mon Jan 20, 2003 6:09 pm

Okay, I know this isn't exactly on-topic, but I am looking at my Haynes manual and I have 2 CEL codes that seems to be related to MAFs. Code 23 says "open or shorted airflow sensor circuit" and code 49 says "use of incorrect airflow sensor". These are both related to the MAF, right?

I am going to do a diagnostic soon to see if I have any codes that aren't trippin the CEL. The hesitation is drivin me nuts and I want to fix it. Right now I have a junkyard MT MAF on my MT car, but it behaves the same way as my olf MAF...

I am not blowin black smoke, and my gas mileage is great, so is it really the MAF anyway?

vrg3 · Post by **vrg3** » Mon Jan 20, 2003 6:19 pm

Those are indeed both related to the MAF, and it is also possible for the MAF to be bad without throwing a code.

I've gotten some bogus MAF and injector trouble codes before when I was teaching someone to drive my car and they stalled it out. When the engine stalls the ECU probably gets really confused and could easily believe it's getting a bad reading from a sensor. I don't know what exactly you mean by "doing a diagnostic" but you should probably do a D-Check procedure to see if the codes come up again.

suberboy · Post by **suberboy** » Mon Jan 20, 2003 6:58 pm

thanks for the input everyone

Vrg3, Thanks for the offer! I am very interested in buying it but I don't know what to offer you for the MAF since I have never bought one. I am also, no offence intended, concerened about buying something that I haven't been able to look at before hand.

I did find out some good info from a local subaru dealer about the MAF. The '91-'94 turbo legacy all have the same part # and so does every '90-91 manual legacy.

now if I go searching in the junk yard how do I know what year the car is, is it in the VIN #?

boostjunkie · Post by **boostjunkie** » Mon Jan 20, 2003 7:14 pm

Take a look at Legacy777's car . . . there should be a picture somewhere.

The 90-91 legacies all had different headlights than the 93-94s. That's a dead giveaway.

vrg3 · Post by **vrg3** » Mon Jan 20, 2003 8:35 pm

Ah ha, there's the rub. 90-91 MT Legacies had the metal housing sensors while 92-94 ones had the plastic housing sensors. Cool.

If the headlights are still on the car, that's definitely the easiest way to tell. The taillights are very different too (the center bars on the 90-91 Legacies have no lights built into them). If the headlights and taillights are both gone, you can still use the VIN; just look at the 10th character. 'L' is 1990, 'M' is 1991, 'N' is 1992, 'P' is 1993, and 'R' is 1994.

I definitely understand your concern about buying it sight unseen. I did swap it into my car and the car ran the same as before. My car does have an idling problem but it didn't seem to get better or worse when I swapped the sensor. I bought this sensor for $70 plus shipping from someone on eBay... I'd sell it to you for what it cost me, since I'd like you to use it. In all honesty, though, you're likely to be able to get one for less from a junkyard, assuming you find a car. I was at a junkyard this past weekend that charged something like $40 or $50 for an import MAF sensor, but there weren't any Legacies with this sensor there. If you get one from a junkyard you'll probably want to clean it out carefully if it's been exposed to the elements.

suberboy · Post by **suberboy** » Tue Jan 21, 2003 3:59 pm

hey vrg3,
I appreciate the honest and helpful answers and will buy the MAF from you for $70. I wouldn't mind going and digging around in the junk yards but with school and work I don't know when I will have time and it looks like I will be able to do my motor swap very soon.
How would you like payment?

P.S. don't suppose you have an auto legacy and would like the STi shift knob for it? I have a new one I bought thinking it was the one for a manual. I should have asked more questions before buying

vrg3 · Post by **vrg3** » Tue Jan 21, 2003 4:30 pm

I once had an auto Legacy, but no more... If you have other cool stuff you might want to trade for or towards the MAF sensor I'll be happy to hear it.

Why don't you PM me your shipping address and I'll figure out how much the total cost with shipping will be? I'll get it ready and pack it securely. PayPal's the easiest way to exchange money since it's quick. Let me know...

suberboy · Post by **suberboy** » Tue Jan 21, 2003 4:39 pm

vrg3, just sent you a pm with my info.

Noah

mile hi · Post by **mile hi** » Sat Jan 25, 2003 3:53 am

Some of the early n/a Legacy's did have the metal case I think it was the manual trans models and the other had the black case. These are hot wire MAFs and the hot film was on the automatics. One big difference is the inside diameter the black plastic ones are close to 2 3/4" if you look through one. They all put out about the same voltage but differ in response time.
AL(CO)

Post by **Legacy777** » Sun Jan 26, 2003 3:07 am

Yeah.....Al's right about the hot wire & hot film for auto & manual trannies

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MAF questions (Milehigh can you help?)

MAF questions (Milehigh can you help?)