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Genchi Genbutsu
Genchi Genbutsu, Toyota Master Technician
Category: Toyota
Satisfied Customers: 4015
Experience:  Toyota Certified Master Diagnostic Technician, ASE Master Technician with L1 Advanced Engine
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what are some symptoms of a bad mass air flow sensor. would

Customer Question

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: 3 years ago.
Category: Toyota
Expert:  Genchi Genbutsu replied 3 years ago.

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.

Customer :

ok is there any way to test it

Genchi Genbutsu :

Do you have an oscilloscope?

Customer :

no i dont

Customer :

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.

Customer :

so that would cause my problem

Genchi Genbutsu :

Yes it very well could.

Customer :

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?

Customer :

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.

Customer :

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

Customer :

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?

Customer :

no y

Customer :

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!


Customer :

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.

Customer :

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

Genchi Genbutsu :

No.

Genchi Genbutsu :

They are independant.

Customer :

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

Genchi Genbutsu :

Correct.

Customer :

would running without tps cause maf to go bad

Genchi Genbutsu :

No.

Customer :

ok do they set tps buy a computer

Genchi Genbutsu :

By DVOM (multimeter)

Customer :

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

Genchi Genbutsu :

Have you ever done this type repair before?

Customer :

no

Customer :

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.

Customer :

so thats the bottom terminal and third terminal right

Genchi Genbutsu :

Correct.

Customer :

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.

Customer :

yea mine closed starts at .44

Genchi Genbutsu :

what about with it at full throttle?

Customer :

it deflects out

Genchi Genbutsu :

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

Customer :

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.

Customer :

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).

Customer :

ok would one from a junk yard work

Genchi Genbutsu :

That would be an option yes.

Customer :

ok thank you for ur help

Genchi Genbutsu :

My pleasure.

Customer :

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

Customer :

closed it set at .2 full open is 4.2

Customer :

would maf be causing that

Customer :

it cuts out at 1500

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