Crx Starts but as soon as I hit gas it dies and has cel code 3, before this OEM sensor was melted, changed it for a skunk 2 4 bar map sensor. Ecu is chipped P28.

 

Did you change the tune to accept a 4-bar MAP sensor? You can't just go from a 1-bar MAP sensor to a 4-bar MAP sensor without changing the MAP sensor scaling in the tune.

 

Gave the ecu to tuner he tuned for the map sensor but now it only revs to 3-3,500 rpms, with solid cel and still map sensor cel.

 

Your MAP sensor melted too? Some of the glue(?) on the bottom of mine melted off leaving a drippy mess, and I have drive-ability issues too. No CEL though. So I was looking for similar info. I read a little bit of service info and found this:

and

I wonder if the Skunk MAP works differently as far as voltages go though. Probably depends how the tuner did it... no idea how tuning these things work.

 

The way these sensors work is they convert pressure to a 0-5V signal. The difference is that the stock one only has a range of 1790 mbar (25.96 psi) and the typical 4-bar sensor has a range of 4228 mbar (61.32 psi). Remember that these are Manifold Absolute Pressure sensors, so the reading is the manifold pressure plus atmospheric pressure. Subtracting out atmospheric pressure (standard is 14.70 psi / 1013 mbar, but this can vary depending on elevation and current weather conditions) you get a range of 11.26 psi for the stock sensor and 46.62 psi for the 4-bar sensor.

What does all this mean? The ECU only cares about voltage - it knows nothing about pressure. Both stock MAP sensor and 4-bar MAP sensor will put out the same voltage, but at different pressures.

Let's look at an example, and we'll keep pressures in mbar for consistency. My Civic idles around 701 mbar below atmospheric pressure (1013 mbar), so 312 mbar absolute pressure. On a stock sensor, this equates to 0.97V. On a 4-bar sensor this equates to 0.32V. So if your car is tuned for a stock sensor but you're running a 4-bar sensor, the sensor is outputting 0.33V, which the ECU is interpreting as 75 mbar absolute pressure, or 938 mbar below atmospheric pressure. It thinks it's in a deeper vacuum than it is, so it's going to under-fuel and cause it to run poorly.

 

Thanks for the info!

Do you think the melted glue on the bottom of my MAP sensor would indicate a problem internally? It held vacuum but I never tested the voltage coming in/out.

No codes for it, but my car seems to be running hella rich and basically undrivable.

 

I haven't experienced melted glue coming out of a MAP, but i would either try testing or just replacing it.