floating map signal

[Denmark]

Hi All,

I´m right now having a floating map signal, meaning when the car is cold, its at 100kpa, then when the car have been driven for around 20-30km,the car begins to have trooble to run at anything from idle to 2000rpm,

Today i  then found out that when the car begins to have trooble, and i turn of the car, and put the ignition on again, the kpa is at 95 kpa, if i start the car it will run like crap, but if i again calibreit the sensor offset again, so its at 100kpa, it will run fine again,
then when the car is cold, its at 105kpa.

The 5v suply wire is shared with lots of other things, like TPS,fueltank map,tumblervalves, and its run of the EC36 pin, that says TPS supply, i have never had this problem before, but i have also allways used the tps supply for tps, and 5v sensor supply for the map sensor,
But in the wiring in the New age Impreza, there is only one 5volt supply at the Ecu, that splits out to all the other parts.

So i was just thinking if any of You have had this problem, and the cure for it?

Tomorrow i will mount a vems mapsensor from my legacy that i know works, and then se if it´s the oe map sensor that is giving me this problem....but i suspect it to be...

As the scaling cant be made right... strange scaling Subaru uses


/Skassa

[rob@vems.co.uk]

The TPS supply pin, EC36pin29 has a resistor to make the +5v a weak supply, its only for the TPS.
Use the 5V supply EC36pin28 to drive your 5v sensors.
I am not sure what a fuel tank map or a tumbler valve is, but they sure as hell shouldn't be driven from the VEMS unless you can quantify the current that they're drawing.

Rob

[Denmark]

"The TPS supply pin, EC36pin29 has a resistor to make the +5v a weak supply, its only for the TPS.
Use the 5V supply EC36pin28 to drive your 5v sensors."


This is also what i normally do, but on this impreza the oe wiring have only one 5v supply at the ecu, this is then split out to all the sensors that needs a 5volt suplly.

Today, i will mount a new mapsensor, and take the feed from pin 28, and make new wiring to the new mapsensor,
Hopefully this cure it.
I found out this morning that i also have to turn of accel enrichment, and if i do that , the car will drive fine, just missing the low input enrichment


Thanks,
Skassa

[Denmark]

Tonight i put on a vems 400kpa mapsensor, and made external wiring for this, so it doesnt run with the oe wiring,
This helped with the map signal, but i then found out that the tps was also floating.

I then took off the plugs of the old oe map sensor, and the tumbler valve sensors and engines, the tps then changed from showing 0procent to showing 7procent.

And the car drives great now, so i will test again tomorrow,as it needs to go on a trip at minimum 30km, to see if the problem have gone away, but i think it have.



/Skassa

[rob@vems.co.uk]

I'm betting that you will need to make up a separate 5V supply to drive the axillary loads.  An LM7405 might have enough capacity to supply the current but you will need to find a method of protecting it from voltage spikes.  I had a nice design that used a power transistor and a zener diode on its base but I've long since lost it.