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what are some symptoms of a bad mass air flow sensor. would

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it cause ur truck studder...
what are some symptoms of a bad mass air flow sensor. would it cause ur truck studder or miss under power. my truck studders or misses when u push heavy on the gas. but if u easy on gas it it ok
Submitted: 7 years ago.Category: Toyota
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Answered in 1 minute by:
12/24/2010
Toyota Mechanic: Genchi Genbutsu, Toyota Master Technician replied 7 years ago
Genchi Genbutsu
Genchi Genbutsu, Toyota Master Technician
Category: Toyota
Satisfied Customers: 4,396
Experience: Toyota Certified Master Diagnostic Technician, ASE Master Technician with L1 Advanced Engine
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Genchi Genbutsu :

I think you just described them. Yes, it will make the vehicle studder and miss as it will also cause low power, bad gas MPG's etc.

JACUSTOMER-9nvzo5wx- :

ok is there any way to test it

Genchi Genbutsu :

Do you have an oscilloscope?

JACUSTOMER-9nvzo5wx- :

no i dont

JACUSTOMER-9nvzo5wx- :

my truck it runs gd when sitting in neutral. and u rev it up it ok . but when u put it in gear and give it gas fast it studders and seems to miss. but if u ease on the gas it runs ok. seems to only do it when u need power to move would that be a mass air flow sensor going bad

Genchi Genbutsu :

This is a vane type MAF and has a door that will move along a resister. What happens is that the resister will get a break or gap in it and when the needle moves along it, the sinal to the computer will drop out causing these symptoms. An oscillioscope would allow you to see the break or weak point via a scanned graphed. The MAF signal is very integral to the engine performance and is needed to 'see' how much air is entering the engine for Fuel ratio. That is also why Toyota switched to a non-contact type MAF.

JACUSTOMER-9nvzo5wx- :

so that would cause my problem

Genchi Genbutsu :

Yes it very well could.

JACUSTOMER-9nvzo5wx- :

ok can u tell me how to put a tps sensor on i bought a new one and when i put it on it runs bad

Genchi Genbutsu :

Can the TPS be adjusted on this 3.0L?

JACUSTOMER-9nvzo5wx- :

the screw holes are slotted so i would think so

Genchi Genbutsu :

The best way is to install the new one in about the same position as the last but before removing the old one, take a DVOM (multimeter) and perform a resistance check of the sensor. This way you can fine tune the new one to the same resistance as the old one and the engine will have the same performance.

JACUSTOMER-9nvzo5wx- :

i put it on plug it in and when u give it a lil gas it cuts out bad

JACUSTOMER-9nvzo5wx- :

when i got truck it didnt have one on it the guy was running it with out it

Genchi Genbutsu :

Thats a bad sign that he was running this truck without a TPS installed. Have you had a repair shop look at this yet?

JACUSTOMER-9nvzo5wx- :

no y

JACUSTOMER-9nvzo5wx- :

running without one wut would it do

Genchi Genbutsu :

I would think that it would be best to have a professional repair shop just set up the TPS and then go from there on the continued Diagnosis.

Genchi Genbutsu :

running without one wut would it do Yes, absolutely!


JACUSTOMER-9nvzo5wx- :

wut would it cause for prob

Genchi Genbutsu :

Exactly the problems you are having. The TPS and MAF will work together for the Computer to run the engine. It would be like you trying to play football blindfolded.

JACUSTOMER-9nvzo5wx- :

ok so say maf is bad would that make it hard to set tps

Genchi Genbutsu :

No.

Genchi Genbutsu :

They are independant.

JACUSTOMER-9nvzo5wx- :

so when i set tps that may help maf to work right

Genchi Genbutsu :

Correct.

JACUSTOMER-9nvzo5wx- :

would running without tps cause maf to go bad

Genchi Genbutsu :

No.

JACUSTOMER-9nvzo5wx- :

ok do they set tps buy a computer

Genchi Genbutsu :

By DVOM (multimeter)

JACUSTOMER-9nvzo5wx- :

i have a mutimeter is there a way i can adjust it

Genchi Genbutsu :

Have you ever done this type repair before?

JACUSTOMER-9nvzo5wx- :

no

JACUSTOMER-9nvzo5wx- :

i put tps on before but never had to adjust one like this on

Genchi Genbutsu :

This may not make much sense and it would be best to let a professional repair shop you trust perform this installation but what you will do is set your DVOM to resistance and back probe the TPS at E2 and VTA and set the resistance to 0.2 and 0.8 at closed throttle and 3.3 and 10 Ohms at wide open throttle.

JACUSTOMER-9nvzo5wx- :

so thats the bottom terminal and third terminal right

Genchi Genbutsu :

Correct.

JACUSTOMER-9nvzo5wx- :

put multimeter to the place where u out pos to neg and it beeps to test that

Genchi Genbutsu :

Set it without the connector installed, just by itself.

JACUSTOMER-9nvzo5wx- :

yea mine closed starts at .44

Genchi Genbutsu :

what about with it at full throttle?

JACUSTOMER-9nvzo5wx- :

it deflects out

Genchi Genbutsu :

Thats not right. It should be 3.3 to 10 Ohms.

JACUSTOMER-9nvzo5wx- :

ok i did it wrong sorry it is .2 closed open 5,3

Genchi Genbutsu :

Then it is Ohming out as good and will want to replace the MAF.

JACUSTOMER-9nvzo5wx- :

are they expensive

Genchi Genbutsu :

I dont know for sure as I havn't priced one out in awhile but please only use a Toyota MAF from a Dealer as aftermarket ones are very untrust worthy. Thats why they are much cheaper (from memory).

JACUSTOMER-9nvzo5wx- :

ok would one from a junk yard work

Genchi Genbutsu :

That would be an option yes.

JACUSTOMER-9nvzo5wx- :

ok thank you for ur help

Genchi Genbutsu :

My pleasure.

JACUSTOMER-9nvzo5wx- :

ok i got it set now when i give it a lil gas it surges bad what cuases that

JACUSTOMER-9nvzo5wx- :

closed it set at .2 full open is 4.2

JACUSTOMER-9nvzo5wx- :

would maf be causing that

JACUSTOMER-9nvzo5wx- :

it cuts out at 1500

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featured content

Symptoms of a bad mass air flow sensor

There are many signs that you’ve got a dirty or bad mass airflow sensor (MAS), starting with a Check Engine Light.

That, of course, could mean practically anything. You’ll need to consider what else your car is doing to determine if it’s a MAS problem.

A MAS determines the mass of air entering a vehicle's fuel injection engine, and passes that data to the Engine Control Unit, or ECU. The air mass information is necessary for the ECU to correctly balance and deliver the correct amount of fuel to the engine.

When a vehicle's MAS is faulty or defective, it can cause a variety of problems, and usually results in very poor performance from your engine. Problems with the MAS arise most often with older cars, largely because newer models have a built-in cleaning system for the MAS, similar to a self-cleaning oven.

Analyzing symptoms of a faulty mass airflow sensor

A faulty MAS will cause problems similar to low compression or low vacuum, and will also show symptoms similar to when your vehicle has low fuel pressure from a faulty fuel pump. Here are some of the most common symptoms of a faulty mass airflow sensor:

  • Runs rich at idle or lean under load
     
    These symptoms indicate a MAS that has a contaminated hot wire, that is, something acting like insulation. The fix is as simple as cleaning the MAS, as explained below.
     
  • Constantly runs rich or lean
     
    This results from too little or too much airflow into the engine. This is hard to detect, though a technician can uncover the problem  by checking out fuel trim status. This problem requires replacement of the MAS.
     
  •  Rough idle or random stalling

    This indicates a failed MAS that’s not sending any airflow information to the engine. Again, this calls for a replacement.

Other symptoms include:

  • The engine is hard to start or turn over
     
  • The engine hesitates or drags while under load or idle
     
  • Hesitation and jerking during acceleration
     
  • The engine hiccups

 

If you believe you have a problem with your car’s MAS, it’s usually best to take it to a technician. However, if you think your problem is just a dirty part, you can clean it yourself.

In fact, experts recommend that you clean this part every six months, or every time you change your oil.

Open the car’s air box and pluck out the MAS with a flat head screwdriver, being especially careful not to touch the fragile wires.

Then place the sensor into a plastic bag filled with rubbing alcohol or a special cleaning solution available at auto parts stores. Swish the MAS around in the bag until it’s clean. Let it sit for 20 minutes or so, allow it to dry and replace it.

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Genchi Genbutsu
Genchi Genbutsu
Genchi Genbutsu, Toyota Master Technician
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