M.A.F. sensor testing

[Froggy69]

can any body tell me how to test the m.a.f. sensor or post a link to a place that tells me how to test it?

this is on a 96' sub

[MT-2500]

You need a scanner to check the data/reading on it
Watch air flow and Baro readings.
First step is clean it with quick dry electrical cleaner and then clean it again for good measure. And then if it does not work right replace it.

Here is a repair info link.
http://www.alldata.com/products/diy/index.html

What engine and trans and Mileage?
Why are you asking about it? What is the problem? Any check engine lights?
What is it doing or not doing?
K @ N filter on it?
MT

[Froggy69]

getting too rich error code on both banks.

it has about 125,000 miles on it,350 c.i.d.,w/automatic.it does have a k&n filter

i have done the plugs,cap,rotor,wires,fuel filter,and cleaned the m.a.f. sensor with brake cleaner(read about using brake cleaner from a search on the error codes i have) used almost the full can.

[MT-2500]

What are the code no.?
What is the fuel pressure readings?
What kind of plugs did you feed it?

Any hard starting cold ? Hard to start cold?
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings,and code no.
MT

[Froggy69]

p0175 and i believe p0172(not quite sure on the 0172 code but they are for bank 1&2 too rich). i also think he said the scanner showed a misfire but he didn't tell me a code for it.he asked me if i had done a tune up and fuel filter rescently,i told him i had done the tune up but not the filter so he told me to do the filter.

i don't have access to a pressure gauge for the fuel,might have to look into getting one.

the plugs are the bosch platinum.not sure about the excact plug though.

btw thanks for all the help you are giving.

[2000CAYukon]

Originally Posted by Froggy69

the plugs are the bosch platinum.not sure about the excact plug though.

If you search this forum (and many others) you will find that the Bosch Platinum plugs have caused many problems on GM cars and trucks.

I highly recommend that you replace them using AC Delco Platinums instead.

//2000CAYukon

[MT-2500]

Originally Posted by Froggy69

p0175 and i believe p0172(not quite sure on the 0172 code but they are for bank 1&2 too rich). i also think he said the scanner showed a misfire but he didn't tell me a code for it.he asked me if i had done a tune up and fuel filter rescently,i told him i had done the tune up but not the filter so he told me to do the filter.

i don't have access to a pressure gauge for the fuel,might have to look into getting one.

the plugs are the bosch platinum.not sure about the excact plug though.

btw thanks for all the help you are giving.

As 2000caYukon said bosch plugs are a no no.
Pitch them in the trash can or take them back and get the right AC-Delco plugs for it,
Get rid of that missfire and check out that fuel pressure and check over all other sensor data in the computer with a scanner.
On the K & N filter clean it and go real easy on the re oil end.
The oil out of a K & N can give a Mass air flow sensor head ackes.
Let us know how it does with the good ac plugs in it.
MT

[Froggy69]

will do on the plugs.

as i said earlier THANKS for all the help.

[Froggy69]

changed the plugs out (person i talked to at auto zone said i shouldn't have been sold those plugs,so some of the people there no of the problem) and put a regular fram air filter in tonight.will see what happens tomorrow

[Froggy69]

i still have the misfire and the 0172 error code(bank 1 too rich) which before i had the 0175 also,so the plugs helped some

the guy at the auto parts said i most likely had a clogged injector,but my dads neighbor(dealership mechanic)said to replace the pressure regulator,he had the same problem on his tahoe.so it looks like i will be doing a pressure regulator when i'm off next week. sure hope this is it because this is turning into a real big headache.

[Blue Bowtie]

Before you replace the regulator (not a bad chore, but also not a ton of fun in a CPFI spider) you really should check the standing and running fuel pressure. I've been there once or 30 times:



If there is no pressure difference between KOEO and running, or little difference, the regulator may be leaking through the diaphragm. If there is a 4-7 PSIG difference, you may be wasting your time throwing parts at it without a full diagnosis. The regulator (GM 17113203) is no bargain at $86.39 net.



Add about $20 for the upper plenum gasket set, and you may be wasting six hours and a fistful of Hamiltons on "education" that could better be spent on a pressure gauge. With that gauge, you can test power-up pressure, running pressure, and standing pressure after shut-down. These three indications (and their comparison) can tell you a lot about the pump, FPR, and injector poppets. It may save you from looking at the fuel system/injector spider entirely.

[MT-2500]

Originally Posted by Froggy69

i still have the misfire and the 0172 error code(bank 1 too rich) which before i had the 0175 also,so the plugs helped some

the guy at the auto parts said i most likely had a clogged injector,but my dads neighbor(dealership mechanic)said to replace the pressure regulator,he had the same problem on his tahoe.so it looks like i will be doing a pressure regulator when i'm off next week. sure hope this is it because this is turning into a real big headache.

10-4 on Blue Bowtie's check that fuel pressure.

I did not catch what year. Fuel pressure is different on diffrent years.
But here is some guide lines on fuel pressure checking.

Checking fuel pressure or Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.
MT

[Froggy69]

took the sub. into the shop today.the fuel pressure leaks down pretty fast when the pump is turned off.the guy said my lower intake gasket could be leaking also,and that he recomends that i replace the fuel meter body as well(sais there is a factory upgrade for the old one) needless to say he wants $900 to fix it and that price is with my dist. being good. he also said not to drive the vehicle telling me that with the possibility of the lower intake leaking the motor could have damage to the bottom end and the motor could go at any time.

[MT-2500]

Originally Posted by Froggy69

took the sub. into the shop today.the fuel pressure leaks down pretty fast when the pump is turned off.the guy said my lower intake gasket could be leaking also,and that he recomends that i replace the fuel meter body as well(sais there is a factory upgrade for the old one) needless to say he wants $900 to fix it and that price is with my dist. being good. he also said not to drive the vehicle telling me that with the possibility of the lower intake leaking the motor could have damage to the bottom end and the motor could go at any time.

You need to have it checked by someone that knows what they are doing.
Leak down is usually caused by fuel pump leaking back or a bad fuel pressure regulator.
On a 96 they do not have a fuel meter body. Just a injector case that holds injectors and fuel pressure regulator.
The fuel pressure regulator or injectors can be replaced seperate.
On the lower intake did he test it or check it out or just figure it could be leaking?
900$ is high dollar repair so make sure what you really need.
What was all of the fuel pressure readings?
MT

[Froggy69]

did not see any of the fuel pressures with the truck running.only got to see it with just the key turned on,it went over 50 then it shut off and dropped pretty fast.as for the fuel meter body,he sais he has put the fuel meter body(sais its a gm upgrade)on other vehicles like mine and that they got better fuel mileage.

what makes it bad is i stopped into 2 other shops to ask how much they would charge me to see exactly what was wrong and neither of them wanted to hear what the truck was doing and what i had done so far to correct the problem.they just wanted to pull the codes.

i think i'll do the pressure regulator when i get the time and hope for the best.