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Thread: Is my MAP sensor bad?

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2016-04-03 13:01:01
Is my MAP sensor bad?
I'm having trouble with my MAP sensor I think. Runs pig rich.

Sensor voltage is like 3v at idle and drops when I rev it up........

isn't it supposed to be the other way around? Higher voltage with less vacuum. Right now its higher voltage with more vacuum.

2016-04-03 13:44:16
What kind of MAP sensor do you have? What BAR rating is it?

How is it wired up?
2016-04-03 13:48:00
Its a 1 bar GM map sensor. Old style of a Saturn car

5 volt ref spliced off TPS
2016-04-04 10:49:21
Without the datasheet I can only estimate;

At idle: 3V/5V=0,6*1000mbar=600mbar

So, at idle you are not producing enough vacuum (Normal should be 250+-100mbar)

Maybe your sensor is bad, or you have a vacuum leak.
2016-04-04 15:00:55
Is my MAP sensor bad?
Maybe my Doug fab intake with huge plenum and 90mm tb is causing the issue.

Even if vac was low the sensor reading should not be going reverse. When I rev it up I get vac. Load goes down. It should go up

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2016-04-04 21:30:39
Anyone here running a 90mm and MAP?

I've read up on a lot of issues with the big TB and using MAP/Speed Destiny.

If you can get it to read vacuum at idle it drops to no vacuum as soon the the huge plate opens 1mm.

I'm also not using an IACV and just the TB screw. Could be causing the issue? I'm going to get some more spec/info for you guys.
2016-04-05 09:05:10
Originally Posted by Haulin200sx

When I rev it up I get vac. Load goes down. It should go up

Correct, something strange is happening.

Where is your MAP connected? Near the tb?
2016-04-05 10:51:24
Is my MAP sensor bad?
It's coming off the middle of the plenum.

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2016-04-05 21:14:36
I would like to add (nothing) here - and just say I hate sensors. Sensors in general are bad.
2016-04-06 14:22:28
Originally Posted by Haulin200sx
It's coming off the middle of the plenum.

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You would actually be surprised how many cars will actually pull more vacuum when you open the throttle plate opposed to how much they draw at idle.

This especially applies to a small engine with large cams and a low idle.

Don't be too surprised if you see your idle MAP sensor reading to be around 5-600mbar and then with a little throttle and higher RPM that it will drop to in the 300mbar range.

Without knowing the rest of the setup and or some logs it is hard for me to say exactly, but I wouldn't be too surprised if this is a larger camshaft engine.
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