Hi guys,
got the following problem with this animal. It got an 7730 ECM, basically the same like the 90-91 C4 ECM just different connectors.
When we depress the throttle the MAP value goes up for a split second and than drops from like 60 kpa at idle to 40 kpa at steady 2000 rpm.

Looking at my own 91 the kpa's go up when I hit throttle, from idle at 30 kpa to something like 50-60 kpa.

Seems like the values are reversed. How can that be???

We measured all wires from the ECM to the sensor. The ground wires from the CTS and MAP were at the wrong spot. Switched those but no difference.

This is an aftermarket set up from Arizona Speed and Marine.

Any ideas how we can get the MAP values in line?

Right now the engine starves gas, when accelerating.

Could it make a difference just reversing the ground wire and the 5 volt reference signal?
It says in the service manual the 3rd wire being the signal, should read 1.6 volts, unfortunately we don't get that, whatever we tried.

We tried 3 ECMS and 2 known good MAP sensors.

Help guys???

Thanks,
Axel

Here is an idea?

http://forum.efilive.com/showthread.p ... throttle-as-rpm-increases