map sensor readings?

cburcham73 · 09-24-2009, 03:05 PM

im working on my 93 full size bronco,i have a miss around 1500-1900 rpms. i suspect my map sensor.im reading 2.523 volts at idle and 2.589 volt wide open.it kinda bounces around as i increase idle. is this a normal reading?tps is fine,as well as my iac,iat,plugs ,wires,cap,rotor,fpr.

crabtruck · 09-24-2009, 03:49 PM

I don't think that's normal,
Before replacing sensor check real good for poor connection,
that sounds like a "hanging" wire measurment.
Particularly sounds as if the ground is not there for reference.

cburcham73 · 09-24-2009, 04:48 PM

just use the vacuum pump to measure the resistance? is the base line 1.5 volt? top end 4-5 volt?

crabtruck · 09-24-2009, 05:37 PM

Unless I'm mistaken you have 3 wires to senser, 5v on Gray, Gnd on Ppl and
the return to ECM is on the green. Changing vac changes green voltage.
.
Don't think you can do resistance check.

Somebody want to check me on this ?
(smartest thing I said)

cburcham73 · 09-25-2009, 08:05 AM

ok. i hooked up the vacuum pump. with 0" i have 2.4 volts. i added 10" inches and was 2.90. still bounces a little when increasing. i dont have any codes. the part number on the map is E7EF-9F479-A2A. what 3 digit stamp are you talking about?

Case 7230 · 09-25-2009, 08:30 AM

I am by no means an expert but I think you are measuring the wrong data. As I understand it the MAP sensors output is a frequency. So as you increase the vacuum on the MAP sensor the frequency should increase.

cburcham73 · 09-25-2009, 09:03 AM

is there a way to check it without ALL the special tools? i have a dig.volt meter and a vacuum pump.

crabtruck · 09-25-2009, 10:45 AM

OK, so I had a tard moment.

I sincrely apologize.
Codes I asked about should have been a give away.
Codes you might have seen would actually have been 22,72,126,128,129
or possibly 121,124,125. Not even close. I'll edit the above post.

Case is on his game catching my error, there should be a freq shift.
A voltage of around 1.5 should be present for the freq to piggy back on.
Your voltage read strikes me as too high and either is caused by poor connection
or bad sensor. Try the test below if your DVM allows and check connections.
The way it's going Case, you better proof read this too.

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

crabtruck · 09-25-2009, 10:52 AM

Round of applause please for Case,
bringing Truth to America !

Many brains makes this a better place.
Next time I'm bringing mine too.

cburcham73 · 09-25-2009, 12:44 PM

thanks guys. i went up and bought a map sensor and it runs alot better.part 2 of the gremlins deals with my idle.with all my acceseries on ac,lights etc when i rev it up and release it falls to about 600rpms and my volt gauge drops then rpms pick back up to normal.it only does it with everyting on...turn them off and it revs and returns normal.

09-24-2009, 03:05 PM	#1
cburcham73 Senior Member Join Date: Aug 2008 Location: williamsburg virginia Posts: 183	map sensor readings? im working on my 93 full size bronco,i have a miss around 1500-1900 rpms. i suspect my map sensor.im reading 2.523 volts at idle and 2.589 volt wide open.it kinda bounces around as i increase idle. is this a normal reading?tps is fine,as well as my iac,iat,plugs ,wires,cap,rotor,fpr.

09-24-2009, 03:49 PM	#2
crabtruck Senior Member Join Date: Jul 2007 Location: on your 9 Posts: 3,365	I don't think that's normal, Before replacing sensor check real good for poor connection, that sounds like a "hanging" wire measurment. Particularly sounds as if the ground is not there for reference. Last edited by crabtruck; 09-25-2009 at 10:46 AM. Reason: tard

09-24-2009, 05:37 PM	#4
crabtruck Senior Member Join Date: Jul 2007 Location: on your 9 Posts: 3,365	Unless I'm mistaken you have 3 wires to senser, 5v on Gray, Gnd on Ppl and the return to ECM is on the green. Changing vac changes green voltage. . Don't think you can do resistance check. Somebody want to check me on this ? (smartest thing I said) Last edited by crabtruck; 09-25-2009 at 10:48 AM. Reason: tard cont.

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09-24-2009, 04:48 PM	#3
cburcham73 Senior Member Join Date: Aug 2008 Location: williamsburg virginia Posts: 183	just use the vacuum pump to measure the resistance? is the base line 1.5 volt? top end 4-5 volt?

09-25-2009, 08:05 AM	#5
cburcham73 Senior Member Join Date: Aug 2008 Location: williamsburg virginia Posts: 183	ok. i hooked up the vacuum pump. with 0" i have 2.4 volts. i added 10" inches and was 2.90. still bounces a little when increasing. i dont have any codes. the part number on the map is E7EF-9F479-A2A. what 3 digit stamp are you talking about?

09-25-2009, 08:30 AM	#6
Case 7230 Senior Member Join Date: Dec 2007 Posts: 547	I am by no means an expert but I think you are measuring the wrong data. As I understand it the MAP sensors output is a frequency. So as you increase the vacuum on the MAP sensor the frequency should increase.

09-25-2009, 09:03 AM	#7
cburcham73 Senior Member Join Date: Aug 2008 Location: williamsburg virginia Posts: 183	is there a way to check it without ALL the special tools? i have a dig.volt meter and a vacuum pump.

09-25-2009, 10:45 AM	#8
crabtruck Senior Member Join Date: Jul 2007 Location: on your 9 Posts: 3,365	OK, so I had a tard moment. I sincrely apologize. Codes I asked about should have been a give away. Codes you might have seen would actually have been 22,72,126,128,129 or possibly 121,124,125. Not even close. I'll edit the above post. Case is on his game catching my error, there should be a freq shift. A voltage of around 1.5 should be present for the freq to piggy back on. Your voltage read strikes me as too high and either is caused by poor connection or bad sensor. Try the test below if your DVM allows and check connections. The way it's going Case, you better proof read this too. 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

09-25-2009, 10:52 AM	#9
crabtruck Senior Member Join Date: Jul 2007 Location: on your 9 Posts: 3,365	Round of applause please for Case, bringing Truth to America ! Many brains makes this a better place. Next time I'm bringing mine too.

09-25-2009, 12:44 PM	#10
cburcham73 Senior Member Join Date: Aug 2008 Location: williamsburg virginia Posts: 183	thanks guys. i went up and bought a map sensor and it runs alot better.part 2 of the gremlins deals with my idle.with all my acceseries on ac,lights etc when i rev it up and release it falls to about 600rpms and my volt gauge drops then rpms pick back up to normal.it only does it with everyting on...turn them off and it revs and returns normal.