Mass flow sensor

Millie

Millie

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Since I can't find the car book for my 2008 Corolla LE, what does the mass flow sensor do? I just had one replaced and now the check engine light is back on after being off for days. (It was ON again a few days after the sensor was replaced, and I was told O2 sensor reads lean and I MAY have a leak in the intake manifold gasket. When I left the car shop Tuesday the light was OFF.)

I have an appointment on the 31st to have them figure out what's going on, but any ideas you mechanically inclined guys have will be helpful. I've already PM'd @ButtonPusher about this, since he does all his own car work, but the more opinions, the better! LOL.
Thanks!
 
I highly doubt there is a leak at the intake manifold gasket. Go to your local autozone and have them read the code. Which is Free. Tell us what the code is and we can better help what needs to be fixed to fix the code

Sent from my SM-G965U using Tapatalk
 
Way I understand, it reads/measures how much air is entering the system and supplies the appropriate amount of fuel.
If bad it'll dump too much or too little fuel ,which causes issues
 
BloodRunsThicker said:
I highly doubt there is a leak at the intake manifold gasket. Go to your local autozone and have them read the code. Which is Free. Tell us what the code is and we can better help what needs to be fixed to fix the code

Sent from my SM-G965U using Tapatalk
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Thanks, I will!
 
BloodRunsThicker said:
I highly doubt there is a leak at the intake manifold gasket. Go to your local autozone and have them read the code. Which is Free. Tell us what the code is and we can better help what needs to be fixed to fix the code

Sent from my SM-G965U using Tapatalk
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I wouldn't bet the farm on that one. Just had the light come on on my 2000 silverado and showed a lean condition. Smoke test revealed a leaking intake manifold gasket. Just got it back from fixing that. Runs great now.
 
All depends. The O2 sensor reads lean as in millivolts or showing short term longterm fuel trims 15 of higher?

100(ish) to 800 (ish). Higher # =rich, lower # = lean

Guessing gets very expensive, data stream tells all.....
 
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Mike Overlay said:
All depends. The O2 sensor reads lean as in millivolts or showing short term longterm fuel trims 15 of higher?

100(ish) to 800 (ish). Higher # =rich, lower # = lean

Guessing gets very expensive, data stream tells all.....
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I have no numbers yet, but will try to get them soon, thanks guys!
 
Mass air flow sensor tells the cpu how much air intake, demanding x amount of fuel. O2 sensors read how much oxygen is in the exhaust, should be zero. O2 in the exhaust can be caused by a bad injector/ or bad plug/ ignition failure , even a leak in the exhaust manifold. But will tell the cpu it’s running lean, and start injecting more fuel. Has your mileage dropped much?
 
foopid stucker said:
Mass air flow sensor tells the cpu how much air intake, demanding x amount of fuel. O2 sensors read how much oxygen is in the exhaust, should be zero. O2 in the exhaust can be caused by a bad injector/ or bad plug/ ignition failure , even a leak in the exhaust manifold. But will tell the cpu it’s running lean, and start injecting more fuel. Has your mileage dropped much?
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Haven't had a chance to check mpg yet. The plugs were replaced a week or so ago. I was told there might be a leak in the intake manifold gasket.
 
Mass air tells the amount of flow but also the temperature (in most cases temp sensor is built in) and determines the amount of fuel to use. If you have un-meter air, such as a leak between the mass air and the combustion chamber, it will read lean. Example Mass air reads 2 kilograms of air moving in the system but you are really getting 2.7 kilograms due to a air leak, the computer will only inject for 2 kilograms. Once the 02 sensor come back lean, the ecu will try to compensate for this and this is where you will see odd short and possible long term fuel trim corrections.


Spray soapy water (little bit at atime) between the mass air and the head while running, if the rpms drop you have found your leak.
 
Djstorm100 said:
Spray soapy water (little bit at atime) between the mass air and the head while running, if the rpms drop you have found your leak.
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Yeah, I have no idea what this means. Plus I can't find the Haynes book I bought for the car. LOL. I'm told to get Advance auto to hook it up and give me some codes, which I will the pass on in this thread.

(I only ever worked on cars with no computers, ones that had actual carbs you could rebuild and adjust, and plenty of workspace around a huge engine! LoL. No idea what I'm looking at under the hood these days....at all. I can check/add fluids and that's about the extent of it.)
 
Millie said:
Yeah, I have no idea what this means. Plus I can't find the Haynes book I bought for the car. LOL. I'm told to get Advance auto to hook it up and give me some codes, which I will the pass on in this thread.

(I only ever worked on cars with no computers, ones that had actual carbs you could rebuild and adjust, and plenty of workspace around a huge engine! LoL. No idea what I'm looking at under the hood these days....at all. I can check/add fluids and that's about the extent of it.)
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Codes will only tell you what dept to shop in. You need data stream. Find a good, fair indy shop and pay the man instead of guessing.
 
Millie said:
Yeah, I have no idea what this means. Plus I can't find the Haynes book I bought for the car. LOL. I'm told to get Advance auto to hook it up and give me some codes, which I will the pass on in this thread.

(I only ever worked on cars with no computers, ones that had actual carbs you could rebuild and adjust, and plenty of workspace around a huge engine! LoL. No idea what I'm looking at under the hood these days....at all. I can check/add fluids and that's about the extent of it.)
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From the red circle to the arrow. You'll have to remove the cover on top of the engine, usually just pulls off or 10mm. Follow the plastic until it meets the alum head. If you have a intake gasket leak, it will be between there.

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Update:
I got the MAF sensor done already, then on New Year's Eve, I got the O2 sensor replaced. Yay, I thought to myself, all is well.
But NOOOOO, just now the check engine light came on AGAIN, and so i headed for Advance Auto, where a nice man hooked the car up and I got codes now....
-PO 171
-Bank 1 too lean

This leads me to think it was the intake manifold gasket after all, and not the O2 sensor?

Anyway, I'm taking it to the same place tomorrow morning, where they'll "evaluate" the situation....again! May not be fixing it then, and I have traveling to do, so I'm not pleased.

Is it really this hard to tell what's causing an issue? Shouldn't the computer tell them what the issue is, without them giving me an either/or? So I got the O2 sensor, which was one possibility, and now we're looking at the gaskets, which was the other?

/Rant over....maybe/
 
In the good news department: I got my shot timer, and now I have my bright green 3" targets/pasters!
 
Mike Overlay said:
Codes will only tell you what dept to shop in. You need data stream. Find a good, fair indy shop and pay the man instead of guessing.
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I tried an indy shop, they had problems with various lights and I quit going there.
This place I've been going to in the last year or so has before this latest issue been great....but maybe not so much now.
 
Button Pusher said:
I should have taken my scanner with me to Battery Oaks. :(
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You'd be a millionaire if you had, because you'd have been able to see into the future!

You'd have known on Sunday that my light would come on today.

I'm going to try real hard to be polite tomorrow, but really, this is getting me a bit peeved.

I would think they'd have actually looked at the gaskets, right, to see if they were leaking? If you have 2 choices, why not look at gaskets first? Then if they're ok, you'd know it must be a sensor....at least in my non-mechanic logic! lol.
 
If you take it to them warm they aren't going to find anything. Leave with them overnight and let them spray it cold.
 
Glade8r said:
Millie, those Corollas do have leaky intake manifolds. They usually only show themselves (p0171 lean code) when the weather gets colder.
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This is the code I just got at Advance Auto! also "Bank 1 too lean".....

So I wonder if I can get my $400 for the O2 sensor back tomorrow, since it seems NOT to have been the sensor, but option #2, the gaskets? LOL. (not holding breath)
 
Glade8r said:
If you take it to them warm they aren't going to find anything. Leave with them overnight and let them spray it cold.
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I'd have to get a rental then, I guess.....
 
Glade8r said:
If you take it to them warm they aren't going to find anything. Leave with them overnight and let them spray it cold.
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Also: Can't they just LOOK at the gaskets and see if there's a gap or something?

I know, you guys are shaking your heads......lol.
 
Millie said:
This is the code I just got at Advance Auto! also "Bank 1 too lean".....

So I wonder if I can get my $400 for the O2 sensor back tomorrow, since it seems NOT to have been the sensor, but option #2, the gaskets? LOL. (not holding breath)
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P0171 indicates a lean condition because the o2 sensors are working. Dummies shouldnt be working on cars:(
 
BatteryOaksBilly said:
Aunt Bea! Call the Man!!!!! Andy
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Mike Overlay said:
P0171 indicates a lean condition because the o2 sensors are working. Dummies shouldnt be working on cars:(
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Don't say that! LOL.
At least I know the new O2 sensor works, right? I got this code today, after the sensor was replaced a week ago. Not sure what the code was at the shop last week. I better ask tomorrow.
 
Schattenreiter said:
I hope you didn't get billed $400 for an o2 sensor. I just had my intake gasket replaced and it didn't cost $400.
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On toyo's, upstream sensor, b1s1, is not an "oxygen " sensor. They are air/fuel ratio (lamba) sensors. A good bit more than oxygen sensors cost. But still a wasted expense in this matter.

Again, without datastream, specifically long term, short term fuel trims along with oxy sensors voltage, guessing is going to get expensive
 
Glade8r said:
If you take it to them warm they aren't going to find anything. Leave with them overnight and let them spray it cold.
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I'll take it in early tomorrow, tell them to keep it and test it and FIX IT, get a rental, load all my gun stuff into it, and head out in hopes of making my shooting appointment in Fayetteville on time. Ta-dah!
 
Mike Overlay said:
On toyo's, upstream sensor, b1s1, is not an "oxygen " sensor. They are air/fuel ratio (lamba) sensors. A good bit more than oxygen sensors cost. But still a wasted expense in this matter.

Again, without datastream, specifically long term, short term fuel trims along with oxy sensors voltage, guessing is going to get expensive
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So is leaving them the car overnight a good way to get this sorted out?
That last paragraph I didn't get at all....how do I get this data, and fuel trims, and voltage?
 
Millie said:
So is leaving them the car overnight a good way to get this sorted out?
That last paragraph I didn't get at all....how do I get this data, and fuel trims, and voltage?
Click to expand...
You will not get the datastream. A good tech with a good scan tool will use this info to decide the cause
Take it back to the first people and let them lick their calf all over again. Any repair they come up with, make them prove to you (how they determine the cause) it will repair the car.No more guessing like the last time.
 
Mike Overlay said:
You will not get the datastream. A good tech with a good scan tool will use this info to decide the cause
Take it back to the first people and let them lick their calf all over again. Any repair they come up with, make them prove to you (how they determine the cause) it will repair the car.No more guessing like the last time.
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I'm taking it back to them tomorrow. We've been at his for a couple of sessions.
 
Put a vacuum gauge on the intake, crank the car and let it warm all the while observing the vacuum reading, if the reading increases there is a good chance your motor has a leaking intake gasket.
 
Dale Flinchum said:
Put a vacuum gauge on the intake, crank the car and let it warm all the while observing the vacuum reading, if the reading increases there is a good chance your motor has a leaking intake gasket.
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I'm printing all this stuff out, so I can ask them a lot of questions! They'll have it all day tomorrow and most of the day Thursday.
 
My scanner shows codes that have not triggered the check engine light. I would have snugged up the intake bolts.

Ask for the old parts back when new are installed.
 
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