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Old 11-06-2017, 01:17 AM   #1
burntrees
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Outback Sport 1998 Impreza Outback Sport MAF sensor CEL after rain (P0103)

Hello, currently my '98 subaru OBS 2.2L non turbo is having trouble starting.
The issue started on a rainy day when I forgot to put the baffles back underneath the air vent on the hood that is directly over the MAF sensor. Parts of the engine bay got wet including the intake area.
When I tried to start it that day, it threw a code and it was undriveable because it idles very hard and will stall shortly after cranking. It seems to be running too rich at idle and running lean on acceleration. It also idles high at over 1000RPM.
I think this is a MAF sensor problem because A. The code (P0103 Mass Air Flow MAF Circuit High) directly points to a MAF issue and B. I forgot to close the rain guards in the hood vents over the MAF sensor and some water got into my engine bay.

Today I tried cleaning it with MAF sensor cleaner and shooting the connection terminals with compressed air, but the cleaner only made it run worse. Surprisingly, the sensor didn't like being cleaned with the MAF cleaner becuase when I start it, it stalls out almost immediately after cranking the engine instead of after 30 - 60 seconds. It also starts to shake a little violently and then die out to 0 rpm and stall.
I tried starting it like this a couple times but I decided maybe I could blow something up if I kept letting it shake so hard.

I tried resetting the code a couple times by disconnecting the battery and it still has the same problem and gives the same code. I am about to buy a new MAF sensor on eBay for about $35, but I don't want to buy something and have it still not work. Can anyone please help me out? Could my MAF sensor still be good, but maybe my a wire is being shorted by moisture somewhere? The air vent is almost directly above the MAF sensor so maybe it got shorted out by the water when I tried to start it. Someone please lead me to the right direction.
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Last edited by burntrees; 11-06-2017 at 01:29 AM.
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Old 11-06-2017, 10:27 AM   #2
Charlie-III
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I'll be honest, I wash our engines once or twice a year, never had issues although I don't run a hard stream at electronics, they do get wet like in your case.

Have you tried pulling the spark plug wires and plugs on that side? If they weren't sealed well, you could have water down the wells.
Yes, that should give a misfire CEL.
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Old 11-06-2017, 12:36 PM   #3
burntrees
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Quote:
Originally Posted by Charlie-III View Post
I'll be honest, I wash our engines once or twice a year, never had issues although I don't run a hard stream at electronics, they do get wet like in your case.

Have you tried pulling the spark plug wires and plugs on that side? If they weren't sealed well, you could have water down the wells.
Yes, that should give a misfire CEL.
What wells do you mean? Like the cylinder well? I'm kind of going on a hunch here, but I'm thinking of just buying a MAF sensor because all signs point to it being faulty.

I will try what you said with the spark plug wires and check them all out. Not that much water got onto the engine bay, but the problem started right after it finished raining and it was running perfectly fine up until then. I'm going to take the MAF sensor apart and try swapping the air filter just in case there is still some moisture inside of the filter or something.
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Old 11-06-2017, 05:19 PM   #4
Charlie-III
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I will guess you missed my point.
I WASH the engines in multiple cars, thus many things get wet.
It's an engine, it gets wet from the road in the rain.

I really DON'T see some water from rain making an issue unless it's getting into one or more sparkplug wells although you would likely get a misfire for that.

Yes, maybe coincidence, you get a failed MAF at the same time, I really don't think it is a little rain through a hood vent unless it was a monsoon.
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Old 11-06-2017, 05:36 PM   #5
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Originally Posted by Charlie-III View Post
I will guess you missed my point.
I WASH the engines in multiple cars, thus many things get wet.
It's an engine, it gets wet from the road in the rain.

I really DON'T see some water from rain making an issue unless it's getting into one or more sparkplug wells although you would likely get a misfire for that.

Yes, maybe coincidence, you get a failed MAF at the same time, I really don't think it is a little rain through a hood vent unless it was a monsoon.
So I guess you're saying that I should check the sparkplug wells? I bought new sparkplugs that I haven't put on a while back, maybe I can try replacing the spark plugs if you think that might help. Btw, it was very little rain, I did open my hood and it dumped a small puddle onto the engine in certain places, but it really wasn't that much. I was thinking since the sparkplugs sit vertically, there is less chance of water getting in through the spark plug wells.

Could it be the air filter got slightly damp (even though I tried drying it by letting it sit in the hot car for a while)? I just took the MAF off again, the filament looks good but the fact that the MAF sensor acted worse after I cleaned it and put it back on makes it highly suspect to me.
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Old 11-07-2017, 11:25 AM   #6
Charlie-III
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Yes, at least pull those plugs and check for wetness. Could be on the plug boots inside the wells or down by the head/plug.

Have you tried running with the MAF disconnected?
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Old 12-01-2017, 01:16 AM   #7
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Originally Posted by Charlie-III View Post
Yes, at least pull those plugs and check for wetness. Could be on the plug boots inside the wells or down by the head/plug.

Have you tried running with the MAF disconnected?
Sorry for late reply. Today I changed the spark plugs and finally got a chance to work on it and visually inspect things again today. I saw the horribly corroded and gunked up spark plugs and was hoping this was causing a misfire of some sort and causing my engine to stall -- unfortunately that was not the case.

I tried running it without the MAF sensor and it idles rough, spits out a ton of excess gasoline from the tailpipe but runs more stable than with the MAF sensor on. When the MAF sensor is plugged in, sometimes it would not even respond to the accelerator petal and reduce the RPMs to 0 regardless. Both idle very rough and shake the engine quite a bit before it died out. I did this a number of times, hopefully not ruining anything else.

Also, I noticed a slightly faint buzzing noise coming from the idle air control connector when I turn the car off and Not sure if this is normal or not but just something I observed. I'm going to take apart my intake assembly and put it back together so I can closely inspect all the parts, vacuum hoses and throttle body.
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Old 12-03-2017, 06:22 PM   #8
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Quote:
Originally Posted by burntrees View Post
Sorry for late reply. Today I changed the spark plugs and finally got a chance to work on it and visually inspect things again today. I saw the horribly corroded and gunked up spark plugs and was hoping this was causing a misfire of some sort and causing my engine to stall -- unfortunately that was not the case.

I tried running it without the MAF sensor and it idles rough, spits out a ton of excess gasoline from the tailpipe but runs more stable than with the MAF sensor on. When the MAF sensor is plugged in, sometimes it would not even respond to the accelerator petal and reduce the RPMs to 0 regardless. Both idle very rough and shake the engine quite a bit before it died out. I did this a number of times, hopefully not ruining anything else.

Also, I noticed a slightly faint buzzing noise coming from the idle air control connector when I turn the car off and Not sure if this is normal or not but just something I observed. I'm going to take apart my intake assembly and put it back together so I can closely inspect all the parts, vacuum hoses and throttle body.
I would check the spark plug wires resistance next - sounds like you have a dead misfire (instead of or in addition to a MAF problem) and if the wires are old there is a good chance they are bad.

2.2 liter engine wires should be between 5,120 and 12,340 ohms each.

2.5 liter wires: #1 5,950 - 13,890 ohms, #2 & #3 6,240 - 14,560 ohms, #4 6,670 - 15,570 ohms.
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Old 12-04-2017, 02:44 PM   #9
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I think some slight buzzing from the idle control valve is normal for a few seconds or so after engine shutdown. I vaguely recall having a loose ground on my intake manifold seemed to cause that buzzing for much longer.

You might try cleaning all engine grounds, and maybe even adding one.
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Old 12-14-2017, 06:13 PM   #10
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UPDATE:
So it was indeed the MAF sensor gone bad. Maybe water got inside of it and fried the circuit board. Idk. I bought a refurbished MAF on ebay for $30, installed it today and cleared the codes.

Took it to the gas station and back no problem. It idles lower than before too and steadily at 300-400. Not sure why, but my guess is maybe the computer is still in learning mode. It hasn't stalled like before so I think it's A-OK. Thanks for the input everyone.

Was super hesitant on buying this new sensor since people online say they rarely go bad, but in my case it was the MAF sensor gone bad.
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Old 12-15-2017, 05:17 PM   #11
Charlie-III
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I will call it coincidence, as I stated, I wash our engines down at least once a year (not putting a high pressure stream on electrical bits) with no issues.
If your MAF was original it was 19 years old, sorta past due.

As to a "refurb" MAF.....ehhhhh......shrug, not me. But if it works for now, you have a direction.

Thanks for the follow up, I hate dead end threads.
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Old 12-16-2017, 12:21 AM   #12
burntrees
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Quote:
Originally Posted by Charlie-III View Post
I will call it coincidence, as I stated, I wash our engines down at least once a year (not putting a high pressure stream on electrical bits) with no issues.
If your MAF was original it was 19 years old, sorta past due.

As to a "refurb" MAF.....ehhhhh......shrug, not me. But if it works for now, you have a direction.

Thanks for the follow up, I hate dead end threads.
If it works it works. I called O'Reileys and they quoted me a MAF sensor for ~$170. Way out of my price range (I'm a broke college student!) Hopefully the refurbished one doesn't crap out, but it's only $30. Just hope it doesn't leave me stranded but I think I'm good. Again, thanks for the help.

I think maybe water could have seeped into the cracks on the top of the MAF sensor and messed up the circuit board maybe. Just a guess. I plan on taking the old one apart to see what it looks like on the inside.
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Old 12-16-2017, 04:48 PM   #13
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Quote:
Originally Posted by burntrees View Post

It idles lower than before too and steadily at 300-400. Not sure why, but my guess is maybe the computer is still in learning mode.
The following might be helpful. I followed these steps myself very recently. Worked well.

Quote:
Originally Posted by GrundleJuice View Post

After resetting the ECU, turn key to on/run for 20 seconds then back to off. Then start it and allow it to idle for 8-10 mins without touching the accel pedal or putting any significant load on it like a/c, head lights, power windows or even changing manifold pressure by applying the brakes. When engine speeds are rapidly falling toward idle, like when depressing the clutch after decelerating in gear, the ECU has to signal the injectors to inject fuel to "catch" it before it gets all the way to idle speed. I assume this is a learned part of the ECU logic since it gets better after some time. If you have an aftermarket or modified intake it may take longer or be impossible to get perfect. Anytime you disconnect the battery it resets the ECU and therefore clears any codes. If you want to find out what DTC was triggering a CEL you should not reset the ECU first.

Last edited by Vancouver98STi; 12-17-2017 at 07:32 PM.
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Old 12-17-2017, 10:07 PM   #14
burntrees
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The following might be helpful. I followed these steps myself very recently. Worked well.
Thank you for the reply, I will try this when I know I am done unplugging my battery for a while.

Is it bad for it to be low idle? I read in the owners manual it should be 700 (+-100), but the way I'm thinking, I'm saving money on gas at stoplights . As long as it doesn't stall I see no problem.
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Old 12-17-2017, 10:37 PM   #15
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Originally Posted by burntrees View Post

Is it bad for it to be low idle? As long as it doesn't stall I see no problem.
Especially with the less than stellar durability of these engines, the last thing I'd want is potentially lower oil pressure while idling (due to the lower idle speed).
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Old 12-18-2017, 01:34 AM   #16
burntrees
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Especially with the less than stellar durability of these engines, the last thing I'd want is potentially lower oil pressure while idling (due to the lower idle speed).
Off topic, but is there a gauge anywhere that can tell me what my oil pressure is? and isn't there somekind of warning that would flash if your oil pressure is out of spec?

Just wondering because I'm thinking of changing my oil pump seal or the oil pump itself. What interval should you change your oil pump?
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Old 12-18-2017, 03:56 AM   #17
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Off topic, but is there a gauge anywhere that can tell me what my oil pressure is? and isn't there somekind of warning that would flash if your oil pressure is out of spec?
By the time the factory oil pressure "idiot light" comes on, the damage has been done. Installing an aftermarket oil pressure gauge (and sending unit) is a very good idea.

Your questions on the oil pump are beyond my knowledge on these engines.
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Old 12-18-2017, 12:43 PM   #18
Charlie-III
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Originally Posted by burntrees View Post
Off topic, but is there a gauge anywhere that can tell me what my oil pressure is? and isn't there somekind of warning that would flash if your oil pressure is out of spec?

Just wondering because I'm thinking of changing my oil pump seal or the oil pump itself. What interval should you change your oil pump?
Quote:
Originally Posted by Vancouver98STi View Post
By the time the factory oil pressure "idiot light" comes on, the damage has been done. Installing an aftermarket oil pressure gauge (and sending unit) is a very good idea.

Your questions on the oil pump are beyond my knowledge on these engines.
There is no "change interval" on an oil pump. When it's apart, you check the rotor to housing clearance.
Unless you run dirty oil or run low/out of oil, there is very little wear on an oil pump.
Yes, seals/O-rings can age and leak, may be worth doing after many years or miles. Worthwhile to check when doing the 2nd or 3rd timing belt since the belt has to come off to check the pump.
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Old 12-18-2017, 01:36 PM   #19
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It's relatively common knowledge that there's a problem with oil pump pickup tubes cracking on certain Subie engines, but I don't know whether this is an issue across all platforms or not.

On my EJ20K, I updated to a later model oil pan along with an aftermarket oil pump pickup made by Moroso.

Last edited by Vancouver98STi; 12-18-2017 at 05:12 PM.
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