Scan tool shows MAP sensor readings are way off

[Jeanda]

...car has been running poorly lately. No codes tripped or stored. Scan tool used to monitor sensor readings and stumbled on the MAP sensors readings not co-'ing with manual specifications.
...In fact, @ idle= (high vacuum)2 volts or less
-key on(engine not running)=above 4volts
@ WOT = (low vacuum)=increased voltage readings. Well I've noticed as I increased rpm, the voltage decreased-indicating that it was increasing vacuum as the rpm increased.
...My question then follows-"do I have a malfunctioning MAP sensor(the book says to replace it), or is the sensor telling the truth and I have a mechanical malfunction?"

[HeadyFirebird'00]

what kind a car yo?

[Camaro2k]

according to the profile ...
Car: 94L32 Camaro
Modifications: Intake/Borla exhaust/Hypertec reprogrammer & pulleys/RKsport headers/NXpress/eib

[Jeanda]

...WHAT DOES THAT HAVE TO DO WITH THE QUESTION!!!!!!!!!.....GAWD, why do I even bother.


...Shiii, I should'nt expect much. Even if this was camaro V6 "101"

[98Camaro3.8]

Originally posted by Jeanda:
...WHAT DOES THAT HAVE TO DO WITH THE QUESTION!!!!!!!!!.....GAWD, why do I even bother.


...Shiii, I should'nt expect much. Even if this was camaro V6 "101"

Damn, settle down. How the hell are we supposed to tell you anything about your car if we don't know what it is? Engines aren't identical...a 3.8 is definetly not the same as a 3.4.

[BLLDOGG]

i say let him fix it himself with an attitude like that.

[FireFighter]

Chill out newbie. You didn't give all the information so, WHY DO WE EVEN BOTHER?

[HBHRacing]

i think you need to learn how a map sensor workes. Key on engine off you will be reading barometric pressure which will be 4+ volts very near 5. As vacuum incresses voltage decreses. You will have 2 PID scan values. Map voltage and Baro voltage. Baro will remain above 4 volts since that will only change with elivation. Map voltage will change with vacuum. On a healty engine at idle you should see around 1.5Volts. as you give it gas decreasing the manifold vacuum the voltage will rise perportional to vacuum.

I think your fine but if you want to test it unplug the vac line and you should see near 5 volts on the scanner with key on. Then use a hand held vac pump to slowly aply vac. Voltage should drop smooth. Go all the way to 19 Hg and it shouldr read right about 1.5 volts and vacuum should hold. If the readings are off or it doesn't hold vacuum it's bad. Otherwise it's not..


and stop yelling at everyone if you expect to be helped.