Normal MAF Readings and Questions

[Gull81]

Hello all,

I have some questions for you all:

First, What MAF readings do you all normally get - trying to establish some ranges. For me, I get around 12g on cold start 4-5 at idle, and about 50-70 at full throttle. I have read that at full throttle, MAF should read about 80% of horsepower, so that doesn't seem quite right, just wondering about your experience.

Second, when you unplug the MAF what happens, I know the computer begins to bypass the MAF. Does it bypass anything else, (ie IAC). How does it know how much fuel / air to add? I ask because I have a misfire that goes away when unpluggin the MAF. I don't know if its the MAF is the culprit or something else that gets turned off with the MAF code.

Third, I dropped one of the MAF bolts and it disappeared ('97 circular type MAF). Anyone know if these have a part # or if they do anything special - they look special.

On the positive side, looking for that bolt pointed me to a big leak that I should take care of. Any advice on that would be good too.

I checked all the valve cover bolts - they were lose - seemed less than hand tight. I tightened all of the except the back right, I couldn't reach that one. I will continue to monitor the oil situation.

 

[gamefreakgc]

Don't get too far into MAF readings. The voltage reading is more important than your scanner's converted measurement. They have a max of 5V and Toyota gave them enough capacity to be used with forced induction which consumes more air than a stock vehicle. You'll never hit 5V or anywhere near it. Even at 11 PSI my highest reading I've seen is 4.75V. Normally if you convert a MAF controlled vehicle to forced induction you have to eliminate the MAF sensor entirely and run a MAP, 4Runners are flexible so you don't have to do that.

Unplugging the MAF will do nothing good. Mine dies immediately if I do that. Have you cleaned the MAF wires though? There's two, one is the intake air temp sensor and the other the airflow sensor. The IAT is tucked away out of the flow.

For bolts, I've used a spare valve cover bolt before. Just a short 10 mm with a washer will do.

 

[Gull81]

Don't get too far into MAF readings. The voltage reading is more important than your scanner's converted measurement. They have a max of 5V and Toyota gave them enough capacity to be used with forced induction which consumes more air than a stock vehicle. You'll never hit 5V or anywhere near it. Even at 11 PSI my highest reading I've seen is 4.75V. Normally if you convert a MAF controlled vehicle to forced induction you have to eliminate the MAF sensor entirely and run a MAP, 4Runners are flexible so you don't have to do that.

Unplugging the MAF will do nothing good. Mine dies immediately if I do that. Have you cleaned the MAF wires though? There's two, one is the intake air temp sensor and the other the airflow sensor. The IAT is tucked away out of the flow.

For bolts, I've used a spare valve cover bolt before. Just a short 10 mm with a washer will do.

I cleaned the MAF, I need to do the throttle body and IAC next. After that maybe the 0^2 sensor, some seafoam and a couple of tanks of gas. if that fails, I will load up the parts cannon.

Good to know that the MAF bolt is nothing special- it looks special so I just wanted to make sure it wasn't a problem.

 

[gamefreakgc]

I cleaned the MAF, I need to do the throttle body and IAC next. After that maybe the 0^2 sensor, some seafoam and a couple of tanks of gas. if that fails, I will load up the parts cannon.

Good to know that the MAF bolt is nothing special- it looks special so I just wanted to make sure it wasn't a problem.

They use the tapered design because the threads in the MAF are soft (brass?) and strip very easy. Just be niiice and slow and you'll be good.

 

[19963.4lsr5]

My MAF warmed up at idle (700rpm) in park is .520lbs/min.

The end of “Help P0171” thread is my troubleshooting.

I had .373lbs/min when I had the TB gasket on wrong and it still idled at 700rpm. So it was enough of a vacuum leak to screw up fuel trims but not enough to cause a high idle.


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[Gull81]

They use the tapered design because the threads in the MAF are soft (brass?) and strip very easy. Just be niiice and slow and you'll be good.

My MAF warmed up at idle (700rpm) in park is .520lbs/min.

The end of “Help P0171” thread is my troubleshooting.

I had .373lbs/min when I had the TB gasket on wrong and it still idled at 700rpm. So it was enough of a vacuum leak to screw up fuel trims but not enough to cause a high idle.


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Thank you, guys.

Do either of know the ballpark of your MAF at open throttle?

 

[gamefreakgc]

Thank you, guys.

Do either of know the ballpark of your MAF at open throttle?

Near full throttle, I was at 26.32 lbs/min.

 

[Gull81]

Near full throttle, I was at 26.32 lbs/min.

Converted to about 200g/s. I don't even come near that at full throttle. I will probably do the IAC just because I should either way and then the first part loaded into the parts cannon will be that MAF.

 

[gamefreakgc]

Converted to about 200g/s. I don't even come near that at full throttle. I will probably do the IAC just because I should either way and then the first part loaded into the parts cannon will be that MAF.

Mine sucks a lot of air though, much more than normal. Do you have the 96-98 "turbine" style MAF or the smaller 99+ MAF? The 96-98's are super pricey but can be easily converted to the 99+ kind, just need a 99+ airbox from the junk yard and swap one wire over in the connector. Will improve airflow.

There's also a super cheap aftermarket MAF on Amazon for $20: Amazon.com: Mass Air Flow Sensor Meter for 1999-2004 Toyota Tacoma & 2000-2009 Toyota 4Runner & 03-08 Toyota Corolla/Matrix 1.8L Replacment AF10029 22204-21010 74-50009: Automotive. Great for diagnosing suspected issues without dropping a lot of money.

 

[Gull81]

Mine sucks a lot of air though, much more than normal. Do you have the 96-98 "turbine" style MAF or the smaller 99+ MAF? The 96-98's are super pricey but can be easily converted to the 99+ kind, just need a 99+ airbox from the junk yard and swap one wire over in the connector. Will improve airflow.

There's also a super cheap aftermarket MAF on Amazon for $20: Amazon.com: Mass Air Flow Sensor Meter for 1999-2004 Toyota Tacoma & 2000-2009 Toyota 4Runner & 03-08 Toyota Corolla/Matrix 1.8L Replacment AF10029 22204-21010 74-50009: Automotive. Great for diagnosing suspected issues without dropping a lot of money.

I have the turbine-style MAF. Thank you! I was wondering if that was possible!

Yes, I bet yours takes in a little extra air haha.

 

[4Reak Show]

Let's get everyone aware and educated.

Engine size is determined by maximum volume of space of all combined cylinders added together. For example, 3.4 liters.

A naturally aspirated engine running at perfect sealing and breathing can only draw in 3.4 liters of air. There is no physical way it can draw in more as that is the mechanical limit. (Again, naturally aspirated).

So when you are measuring the mass of the air, (or mass airflow) you are measuring the physical amount of matter the engine is sucking in. There's a bunch of math involved to convert the grams/sec to cylinders/revolutions etc etc but basically you're checking the engine's reported breathing. The technical term is Volumetric Efficiency. Here is a website with a good Volumetric Efficiency calculator. Volumetric Efficiency Calculator | OTC Tools It is accurate for naturally aspirated engine.

The reason people go over 100% efficient is because the supercharger is supplementing additional air that the engine is physically unable to pull on its own.

All that nonsense I just spewed is telling you that you can take any grams per second reading you want at a given RPM and engine size and plug it into the website calculator. It will work for any internal combustion naturally aspirated engine.

A lower volumetric efficiency number indicated under reporting which flags a false lean condition generally. (Engine is sucking in the correct amount of air physically but the sensor is reporting less, so there is leftover unused air during the combustion process)

Man that was a lot of info. Sorry. I'm in the hospital right now with time to kill.

 

[19963.4lsr5]

I have the turbine-style MAF. Thank you! I was wondering if that was possible!

Yes, I bet yours takes in a little extra air haha.

When you driving down the road holding a steady 50mph what is your LTFT?

If your lean condition is due to a vacuum leak the closer to WOT you get the less apparent it will be. Because manifold vacuum goes down as you open the throttle.

I’ll try and get you a MAF reading at 50mph with the TPS position and engine load.

If I remember I was running 15 LTFT lightly load at 50 when I had my TB gasket on wrong. It idle it was 29.

If you think you have a vacuum leak unplug the IAC and spray everything with brake cleaner. Non flammable stuff if you can find it. You well know when you find it. It will stumble.

My brothers 440 had a volumetric air flow of a 520cid engine. So it is possible to have more airflow than the displacement with the proper cams and heads on an NA engine.


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[19963.4lsr5]

Driving this morning to work at 50mph on a flat road I had 16 to 21 TPS and my load was 38% to 41%

I don’t have MAF on my ScanGauge or DashCommand on my iPhone. Going to add it to my iPhone today I hope.


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[3RDGENGuy]

Let's get everyone aware and educated.

Engine size is determined by maximum volume of space of all combined cylinders added together. For example, 3.4 liters.

A naturally aspirated engine running at perfect sealing and breathing can only draw in 3.4 liters of air. There is no physical way it can draw in more as that is the mechanical limit. (Again, naturally aspirated).

So when you are measuring the mass of the air, (or mass airflow) you are measuring the physical amount of matter the engine is sucking in. There's a bunch of math involved to convert the grams/sec to cylinders/revolutions etc etc but basically you're checking the engine's reported breathing. The technical term is Volumetric Efficiency. Here is a website with a good Volumetric Efficiency calculator. Volumetric Efficiency Calculator | OTC Tools It is accurate for naturally aspirated engine.

The reason people go over 100% efficient is because the supercharger is supplementing additional air that the engine is physically unable to pull on its own.

All that nonsense I just spewed is telling you that you can take any grams per second reading you want at a given RPM and engine size and plug it into the website calculator. It will work for any internal combustion naturally aspirated engine.

A lower volumetric efficiency number indicated under reporting which flags a false lean condition generally. (Engine is sucking in the correct amount of air physically but the sensor is reporting less, so there is leftover unused air during the combustion process)

Man that was a lot of info. Sorry. I'm in the hospital right now with time to kill.

Awesome read!


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[HiLife]

Yes, that was a good read.

 

[gamefreakgc]

When you driving down the road holding a steady 50mph what is your LTFT?

If your lean condition is due to a vacuum leak the closer to WOT you get the less apparent it will be. Because manifold vacuum goes down as you open the throttle.

I’ll try and get you a MAF reading at 50mph with the TPS position and engine load.

If I remember I was running 15 LTFT lightly load at 50 when I had my TB gasket on wrong. It idle it was 29.

If you think you have a vacuum leak unplug the IAC and spray everything with brake cleaner. Non flammable stuff if you can find it. You well know when you find it. It will stumble.

My brothers 440 had a volumetric air flow of a 520cid engine. So it is possible to have more airflow than the displacement with the proper cams and heads on an NA engine.


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520 cid??? That's a freakin' huge engine! Our 3.4 liter engine is a tad over 200, that means it's a 8L+ engine? V10? V12?

 

[sweet88gt]

520 cid??? That's a freakin' huge engine! Our 3.4 liter engine is a tad over 200, that means it's a 8L+ engine? V10? V12?

Old school 440 is a V8

I also subbed this thread for future use.

 

[19963.4lsr5]

520 cid??? That's a freakin' huge engine! Our 3.4 liter engine is a tad over 200, that means it's a 8L+ engine? V10? V12?

It’s a Chrysler 440 with Indy heads with huge valves and big cam. It’s volumetric efficiency was around 120%. I know it was above 100% and not just 102%) I’ll ask him for the dyno specs.


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[Gull81]

Driving this morning to work at 50mph on a flat road I had 16 to 21 TPS and my load was 38% to 41%

I don’t have MAF on my ScanGauge or DashCommand on my iPhone. Going to add it to my iPhone today I hope.


Sent from my iPhone using Tapatalk

When you driving down the road holding a steady 50mph what is your LTFT?

If your lean condition is due to a vacuum leak the closer to WOT you get the less apparent it will be. Because manifold vacuum goes down as you open the throttle.

I’ll try and get you a MAF reading at 50mph with the TPS position and engine load.

If I remember I was running 15 LTFT lightly load at 50 when I had my TB gasket on wrong. It idle it was 29.

If you think you have a vacuum leak unplug the IAC and spray everything with brake cleaner. Non flammable stuff if you can find it. You well know when you find it. It will stumble.

My brothers 440 had a volumetric air flow of a 520cid engine. So it is possible to have more airflow than the displacement with the proper cams and heads on an NA engine.


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MAF around idle was around 4 today:
Image shows reading cruising highway speed and then flooring it (coolant temp in centigrade around 205 on the highway.)

Video show the engine 'shudder' - it's hard to hear on the video, but you can see the engine skip a beat. I assume its a misfire though no code or PID to show it. The second video also shows the exhaust - each 'shudder' is accompanied by a big puff.

YouTube
YouTube

Given it enough time that I am confident it isn't just the computer (though it seems to have gotten a bit better), I will order all the stuff for the IAC job next.

 

[sweet88gt]

Both of your videos are private and can not be opened.