Engine Bogging Down - MAF Mass Air Flow

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Engine Bogging Down - MAF Mass Air Flow

Postby Chuck S on Tue Sep 05, 2017 4:20 pm

Hey Everyone,

I have an 87 XT GL10 Turbo which I got this summer. When I bought it the seller advised me that it bogs down, and sometimes stops every 15 mins or so.
The quick fix is, pop it into Neutral, turn the key off/on, and then she pops right off again running fine.

I brought it into the shop and they replaced the fuel pump for $450 (plus a full assessment), however that didn't fix it. However they said I needed a new one anyhow, as my old one was only putting out 4 and is should be 10.
Anyhow, they think a new MAF will do the trick, for another $400. However I told them I'd have to think about that one, and come back at a later date.
I found some MAF cleaner at Autozone, but when I looked at the MAF I wasn't really sure where to spray it into?
The Subaru shop told me the MAF gets hot and sends out bad data? I guess that makes sense, but just didn't want do dump more $$ into something that doesn't work.

Has anyone had a similar problem, and the MAF replacement did the trick?

Interested to hear any similar stories.

Thanks Austin for getting my login setup!

Thanks to Huck for all of your great advice, really appreciate it : )

Chuck.
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Re: Engine Bogging Down - MAF Mass Air Flow

Postby grossgary on Wed Sep 06, 2017 6:40 am

No way don't do it. They're guessing. Fuel pump was fine and they replaced it for no reason. Saying it needed replaced anyway is likely just a guilty self justification for not fixing your car after $400. If you keep throwing around $400 for guesses a car this age is going to cost you many thousands to own.

Remove MAF and spray cleaner trough it. There are two style 1987 MAFs.

It takes 10 minutes to swap in a used MAF. They fail so rarely that buying a new one is absurd.

A MAF could do that but so could other things.

How are the plugs, wires, cap and rotor?
Those are required maintenance items anyway, Id start there.
Use OEM NGK plugs and magnecor, NGK or other high quality wires.

If it comes to diagnosing and guessing I'd look at used parts:
Read the check engine lights and memeory mode
Used MAF
Used CAS (distributor)
Clean idle controller
Used coil
Gary
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02 OBW VDC H6
06 Tribeca
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Re: Engine Bogging Down - MAF Mass Air Flow

Postby john in KY on Wed Sep 06, 2017 7:38 am

If the engine has the spider-stlye intake than it has the newer still AFM. As Gary suggested, just swap it with a used one. Almost positive the XT6 used the identical one. Sort of screwed if the have the "flapper" AFM but I have never heard of one of these failing.

Check for a ground with on the passenger-side of the engine. It will be attached to one of the intake manifold bolts. This ground is needed to fire the injectors. Good chance if you attempt to remove the bolt it will snap, creating more problems. I would just cut it and slice in a new section of wire and find a new grounding point.

I don't feel the problem is an AFM meter problem. The TPS, throttle position sensor, may need to be looked at.
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Re: Engine Bogging Down - MAF Mass Air Flow

Postby Chuck S on Wed Sep 06, 2017 3:09 pm

Hey Gary & John,

Thanks for the GREAT advice. Yah it sort of made sense these guys were guessing as even though they are a Subaru Performance shop, the guy working on my car wasn't even born when my 87 was made. They said they had to find old paper manuals, and he'd only worked on one in his whole life, so yep, odds are it's a total guess.

I was the only old school car in there, the rest were maxed out WRX's etc.... I felt like a fish out of water.

I'll try and find another shop... Anybody know of one in the Chicago area? haha.

I'll have em check the standard stuff like you said, and take it from there. Thanks for the NGK tip.
They guy I bought it from had put on new spark plug wires, but not sure when the other items have been changed.

I took a quick video of my MAF and engine https://youtu.be/jTPzMwFN9YQ maybe this would help identify which MAF I have.
So would I just remove that intake hose and spray the MAF cleaner in there? (Sorry, my dad was a top mechanic, but it didn't rub off on me, and he's no longer around)

Yah, I don't wanna keep throwing $400-$500 per visit at the shop, and nothing changes. It runs EXACTLY the same after they put in the new fuel pump.

You mentioned "Read the check engine lights and memory mode", and when the engine bogs the "ECM" red light comes on for a bit.
How do I access memory mode, or what could that tell me? It's funny because as soon as I turn it ON/OFF it is just fine for the next 15 mins or so.

I wanna get this thing running good so I can make it down to the Dragon Tail next summer : ))

Thanks so much for your help!

Chuck.
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Re: Engine Bogging Down - MAF Mass Air Flow

Postby john in KY on Thu Sep 07, 2017 8:53 am

From the video, looks like you have the flapper type AFM. Just me but I would be reluctant to use cleaner on it because it is not a hot-wire type.

The ECU is located in the trunk under the package tray. Somewhere in the wiring bundle you will find 2 unconnected wires. One green, other black. Connect the 2 green wires. The ECU has a small "window" that will flash the codes with the key in the run position. A long flash equals 10. Short flashes are single digits. Example: 2 long flashes followed by 3 short equals trouble code 23. There are lists on the web that will decipher the DTCs.

Something to think about. Why does the engine quit running? No spark or no fuel? If the injectors stop firing, problem/solution probably is that ground wire I mentioned.

Post the codes you find.

http://www.ultimatesubaru.org/forum/top ... 1983-1988/
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Re: Engine Bogging Down - MAF Mass Air Flow

Postby crazyhorse_001 on Thu Sep 07, 2017 2:20 pm

That is a flap maf. It can come from any like year subaru turbo. Be sure the numbers on the id tag match. If you feel handy, you can open the top, and look at the solder joints. After 30 yrs its likely some arent as good as they once were. Let me look, i think i have one boxed up here somewhere that i know is good.
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Re: Engine Bogging Down - MAF Mass Air Flow

Postby Chuck S on Fri Sep 08, 2017 1:15 pm

Hi John,

Thanks, I'll hold off on using that spray. I'll check the lights this weekend and see what the codes are.
thanks for the great info!

john in KY wrote:
Post the codes you find.

http://www.ultimatesubaru.org/forum/top ... 1983-1988/

Than
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Re: Engine Bogging Down - MAF Mass Air Flow

Postby Chuck S on Fri Sep 08, 2017 1:17 pm

Thanks much crazyhorse_001 , I'll check and see if I come up with a MAF code this weekend and let ya know.

Appreciate it!

Chuck.


crazyhorse_001 wrote: Let me look, i think i have one boxed up here somewhere that i know is good.
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Re: Engine Bogging Down - MAF Mass Air Flow

Postby neilsh on Fri Oct 13, 2017 6:48 pm

It is quite likely the air flow meter. I had exactly the same symptoms on my '85, 20 years ago. Thought it was bad gas, had the tank flushed, etc, lots of money wasted. I eventually moved and took it to a different dealer and they pegged it as the airflow meter, had it changed and ran great for another 10 years until I sold it.
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