Testing MAF

cherrington17 · 06-09-2009, 05:38 PM

How?

this p0171 is driving me nuts (and hurting my mpg) I tried to replace the upstream O2. Kicked back on immediately. I cleaned the MAF with carb cleaner, kicked on immediately.

I have another MAF here ready to replace it, but i want to know how to test it/them, before hand. I can quickly eliminate, if i need to swap them, if i know what to test w/ my voltmeter.

So... how?

along with that.... i was also told to check for vacuum leaks, and exhaust leaks.. How?

[ion] C2 · 06-09-2009, 06:55 PM

You happen to have a narrowband air/fuel gauge?

cherrington17 · 06-09-2009, 08:16 PM

no. When i say, how do i test it, i mean.. what voltage should it show, when its functioning?

guiguilandry · 06-09-2009, 08:24 PM

you should have a 5 volt and a ground but the signal works with a frequency... in hertz..... and I don't know how much hz = how much volts....

for vacuum leaks, you can try to spray brake cleaner on all the vacuum hoses and all around the intake, normally vacuum leaks makes a hissing sound clearly audible....
for the exhaust leaks let's just say that you would hear it too if there is one big enough to cause that code to set...

I hope that it'll help you a little....

Edited, I hope that you did not spary carb cleaner on your maf while the car was running... if so, there is chances that you burned off the elements into the MAF

[ion] C2 · 06-09-2009, 08:29 PM

Quote:

Originally Posted by cherrington17

no. When i say, how do i test it, i mean.. what voltage should it show, when its functioning?

I asked because tapping into the O2's wiring sometimes sets off this code. It always showed up randomly when I had mine hooked up.

heineck · 06-09-2009, 08:58 PM

which wire do u tap into? my gauge rolls back and forth

guiguilandry · 06-09-2009, 09:06 PM

heineck, you mean that the a/f ratio goes to lean... rich... lean... rich... That's normal that's how a narrowband sensor work... is switch between lean and rich instead of being a linear output like a wideband is.....

AleroB888 · 06-09-2009, 09:09 PM

Quote:

Originally Posted by cherrington17

How?

this p0171 is driving me nuts (and hurting my mpg) I tried to replace the upstream O2. Kicked back on immediately. I cleaned the MAF with carb cleaner, kicked on immediately.

I have another MAF here ready to replace it, but i want to know how to test it/them, before hand. I can quickly eliminate, if i need to swap them, if i know what to test w/ my voltmeter.

So... how?

I have tested a MAF sensor with an o-scope just to see if it was basically functional, but testing one to see how accurate it is would be difficult. Best is just to sub in the other unit. A vacuum leak would make your LTFT's consistently much higher than normal.

cherrington17 · 06-10-2009, 01:17 AM

ltft??

and so the only good way to test it, is to yank the old, put in a new, and clear the code? (see if it comes back?)

dragon8807 · 06-10-2009, 02:47 AM

LTFT = Long Term Fuel Trim

try the other one out, clear the code and see if it comes back or not

heineck · 06-10-2009, 11:05 AM

Quote:

Originally Posted by guiguilandry

heineck, you mean that the a/f ratio goes to lean... rich... lean... rich... That's normal that's how a narrowband sensor work... is switch between lean and rich instead of being a linear output like a wideband is.....

ok thanks i was trippin out cuz i knew i did it right, thanks and mybad for threadjackin cherry

cherrington17 · 06-13-2009, 10:12 PM

replaced my MAF, killed the code. let run for several minutes. Code didn't come back yet. I hope its dead forever.