How would I go about testing the map sensor on my 92 f150 302?

 

On Ford applications, a multimeter that can read
frequency is normally required to check the sensor’s
output. But you can also use an ordinary tachometer
because a tach can display a frequency signal.
Here’s the procedure:
1. Set the tachometer to the four-cylinder scale
(regardless of how many cylinders the engine has).
2. Connect one tachometer lead to the middle terminal
on the MAP sensor and the other tachometer test
lead to ground.
3. Connect the two jumper cables the same as before,
attaching each end terminal on the sensor to its
respective wire in the wiring connector.
4. If you want to measure engine vacuum so you can
correlate it to a specific frequency reading, connect
a vacuum gauge to a source of manifold vacuum
on the engine, or tee the gauge into the MAP
sensor hose.
5. Turn the ignition ON and note the initial reading.
The reading on the tachometer should be about
454 to 464 at sea level, which corresponds to a
frequency output of 152 to 155 Hz.
6. Start the engine and check the reading again.
If the MAP sensor is functioning properly, the
reading should drop to about 290 to 330 on the
tachometer, which corresponds to a frequency
output of about 93 to 98 Hz. No change would
indicate a defective sensor or leaky or plugged
vacuum hose.



OR

When the engine is running MAP takes the BP and subtracts the pressure caused by the engine
to send a frequency (in Hz) to the computer. Testing requires: a vacuum pump with gauge,
a 5V DC supply and a Digital multi-meter with a frequency (Hz) setting.
Middle wire is signal output. To test, removed from vehicle, have vacuum applied to it,
then measure the frequency across the ground and signal (middle) wires,
per list below while 5V DC is applied to the input wire . The list is +/- 3Hz.

in-Hg . kPa .. Hz
00 ....... 0 .... 159
03 ..... 10.2 .. 150
06 ..... 20.3 .. 141
09 ..... 30.5 .. 133
12 ..... 40.6 .. 125
15 ..... 50.8 .. 117
18 ..... 61.0 .. 109
21 ..... 71.1 .. 102
24 ..... 81.3 ... 95
27 ..... 91.5 ... 88
30 .... 101.6 ... 80

 

Thanks for that information subford.

I was thinking using my multimeter to test for voltage not Hz.

I have two multimeters but none of them test for Hz, I suppose I'll have to find one that tests for Hz.
So I would assume the Hz test would be more accurate?

 

The MAP sensor on these trucks always puts out 2.5 volts. No matter what, it's just how its frequency-based system works. Doing a voltage test will not tell you anything at all.

 

Thanks for clarifying that.
I called my local radio shack and they don't have a meter that tests Hz. The auto parts stores don't either.
Would you know which other places that would sell something like that?
I may try online if I can't find one local.

 

I purchased a cheap meter at Harbor Freight that can also measure frequency. Less than $20 a few years ago.

 

Harbor Freight has a $50 meter that can. Keep in mind $40 gets you a new MAP sensor.

 

Sears may sell one.

 

I generally try to stay motorcraft on things like this.
And the MC map is $106 through rockauto.
I don't think I have a problem with mine, just trying to eliminate it from what's causing a shaking motor at idle.

I didn't think about harbor freight or Sears, I'll check their sites to see what they carry in store.

 

The last Sears multimeter I bought was manufactured by the same company that makes Harbor Freight's higher-end "Centech" brand meter.

Here's the HF meter I was talking about:
5-in-1 Digital Multimeter

 

I called my local FH and they didn't have that particular meter in stock.
So out of curiosity, I stopped at a local farm and home and I was surprised they had one that measures Hz.

Not bad price, only $45. It looks like it should do the job.