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MAP Sensor testing
Topic Started: Sep 10 2010, 07:16 AM (7,445 Views)
dayle1960
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Fastest Hampster EVER

What is the procedure for testing the MAP sensor? Also close in line with the MAP sensor is a fuel filter. Can this filter be tested?

thanks
terry
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Memphis metro


Are you getting a map sensor code? If so which code? This determines which test to perform on your sensor. If your engine is having driveability problems and you think it is the map sensor but have no codes, disconnect the electrical connector to the map sensor and if your engine runs better then replace the sensor. Other than check your little filter you can buy a inline filter at the parts store for the cheap.

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metroschultz
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Please just call me; "Schultz"

dayle1960
Sep 10 2010, 07:16 AM
... Also close in line with the MAP sensor is a fuel filter. Can this filter be tested?

thanks
terry
That little filter is a spark arrester/pulse dampener.
It keeps the map sensor safe in the event of a backfire.
I am not sure you can test it.
I would just check to make sure it flows smoothly.
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mwebb
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FOG


3 wires to MAP sensor
on one end labled is 5 volts must be 5 volts dead nutz
on the other end labled is ground must be within 50 millivolts of battery negative

1 is signal . the center pin
peak signal with key on engine off OR WOT about 3.6 volts
this MAP sensor will read pressure above BARO over 3.6 volts .... but it is UNknown if the ECM will read it
low value at hot idle about 1.6 volts headlights on to 1.7 volts headlights off
higher with heater blower on or any additional loads
at decel coasting down hill in gear about 1.4 volts

signal values at 300 feet above sea level . higher elevation will INCREASE signal voltage value s a wee bit , 5volt and ground must never deviate from values above
=====================
the little frantinizer in the vacuum line is a restriction orifice , it dampens the amplitude of individual vacuum pulses from each cylinder generated during the time the intake valve is open .
it could also stop any spark s that may be present in the vacuum line ..... i guess , i had never heard of that particular use for it .
Edited by mwebb, Sep 10 2010, 11:55 AM.
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Memphis metro


I read somewhere as well it protects the map sensor from fumes and oil. It would be intresting to tear one of these apart to see the internal contents. It do look like a inline filter.
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dayle1960
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Metroshultz, enginedoctorgeo, mwebb, thanks for your concise answers. I feel if ALL posters with questions such as mine would 1. State your problem in the subject line CLEARLY, 2. be accurate with the problem you are having in the body of your post, and 3, ask for a specific answer from one of the guys on this forum then the answer should be readily appearant. As an added benefit maybe someone like my self won't have to look to far into the search feature in order to get the answer we need 6 months from now.

It is so much easier to peruse the title of threads instead of individual words within the body of the post. So once again, thanks all for the responses.

terry
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dayle1960
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Enginedoctorgeo:

I pulled the plug out of the MAP sensor and the engine died. I tried it again and it died again. Do I need a new sensor?

mwebb:

Here are the results:: On the wiring harness connector from the ecu, engine,.... with the key on and engine off. The pin closest to the firewall has 13.9 mV. The center pin has 4.9V. The pin closest to the front of the engine has 5.0V.

I tried to test the MAP sensor. I did not get any readings, but then I don't know how to test the sensor, but I guess I did the wiring harness connector correctly.

As far as the inline filter, I disconnected it from the TBI and the MAP sensor. I blew through the bottom end and there was no restrictions. Felt like blowing through a straw.

Thanks
terry
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dayle1960
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bump...
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mwebb
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FOG

http://geometroforum.com/topic/2680128/1/

you must connect to the MAP sensor with the MAP sensor connected in the harness
first key on engine off then -
then with the engine running
use T pins

values are in my previous post
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Memphis metro


(I pulled the plug out of the MAP sensor and the engine died. I tried it again and it died again. Do I need a new sensor?)

Mitchell online says if your engine runs better after disconnecting it, replace it. I would say dying isnt better so do not replace it.

Did you have any map sensor codes before you pulled the plug?
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dayle1960
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no, it was not throwing a code before I unplugged it. I unplugged it and NOW it is throwing a couple of codes. MAP sensor code and vacuum leak. It will clear up. It did before.
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dayle1960
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Yep, I disconnected the battery and low and behold the CEL cleared up.
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mwebb
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dayle1960
Sep 14 2010, 05:41 PM
Yep, I disconnected the battery and low and behold the CEL cleared up.
stop doing that
it will not help your symptom - you waste time waiting for self testing to run

what is 02 sensor voltage at hot idle
and
at 2k rpm hot

should be cycling from 150 to 850mv (millivolts) .15 to .85 volts and back in 100 milliseconds or less
black wire in the bundle of 4 to the front 02 sensor
use
T pin to connect
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Memphis metro


We have never heard what the symptom was! He was just asking about how to test it. LOL
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mwebb
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enginedoctorgeo
Sep 14 2010, 09:37 PM
We have never heard what the symptom was! He was just asking about how to test it. LOL
that s true ....
but what ever it is

bitch slapping the ECM by interrupting supply is not going to improve it
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