MAP sensor problem
 

Ok, ive been tearing my car apart trying to figure out what the heck is wrong with my MAP sensor and ive run out of ideas. The car sat for appx 2 months, and i went to go start it and noticed that manifold pressure was reading 2.8 inches of vacuum. Of course it didnt want to start, ran super super rich. So i thought maybe I had a pack rat nibbling at my harness, so I ripped the entire engine harness out and checked every single termination with a scope. It was fine. I double checked the grounds and the map sensor wires. I threw the harness back in the car, and get the same readings. Replaced the MAP sensor, same readings. All the other sensors are within specs. The sensor is getting 4.98 volts and with the sensor plugged in, the signal wire reads 1.43volts. With the sensor completely unplugged, the Haltech registers the Manifold pressure at around 28 inches.

The Haltech is correctly set to 3BAR.

The sensor does work, when add vacuum or pressure, the readings change. But, it isnt accurate. Has anyone experienced anything like this before?? I need to get my car running again!!!

Try changing the MAP sensor type to something other than 3 bar. Reset the ECU then change it back to 3 bar and reset again.

Tried that. I set it to a 1 and 2 bar sensor, then back to 3. Each time it still registered out of spec.

What should voltage should the MAP sensor be putting out at atmospheric pressure on the sensor wire??

Did you reset the ECU each time? (turn the ignition off and back on again?)

Also, check all your vaccuum lines and manifold gaskets, if there is a nasty vaccuum leak this might also happen. And finally where to you have the vaccuum line connected to?

What ECU is this? is it an E6X with built in MAP sensor? try connectig that and see what happens.

One other possibility is that the signal wire in the map sensor connector isnt reaching the ECU it self, but since you said the reading is changing but incorrectly, it might not be an issue.

Its an E6K. And I didnt clarify, the MAP sensor is reading 2.8 inches of vacuum when the engine is NOT running. It should be closer to 30" Hg when the key is ON, but the engine is not running correct?

If I understood what you're saying then--->
Key on motor not running close to 0.0 inches.
If you're getting 2.8 inches that's not bad. Your altitude can also affect the reading.
There are actually three different 3-bar GM type map sensors. It depends on the manufacturer but the calibrations are a little different from each other. Notting to worry about.
When Haltech designed the E6-K software there was only one 3-bar map sensor readily available so the software was calibrated around that.

Just wanted to follow up with you guys. Thanks Crispeed for the feedback. I drug my MityVac vacuum tester out and checked the MAP sensor readings on the E6K and it reads appx 2 inches off. I tested it with 2 different MAP sensors, similar findings. So, good to know! :)