Map sensor signal wire reading too high on idle for water meth

[Cammy]

Anyone know why this would be caused? The map signal wire reads over 4v at idle... It should be iirc 1.7v?

It's making my water meth spray immediately as ignition is on (even without car on) :/

Other wires are a positive that reads 4.7v and an earth

I'm scratching my head on this one and why the voltage is that high on the signal wire, any help is appreciated.

The wmi kit is devils own stage 2 progressive controller just for reference

 

[Cammy]

Anyone know probable causes?

 

[Dan FR]

What year and engine code is the car? I can have a look at Autodata tonight to see what they should be reading if no-one helps before that.

Have you got VCDS to see what the the ECU is reading from the map sensor? At what voltage does the water/meth kick in? Is the controller adjustable?

 

[Cammy]

The voltage should be iirc 1.8v on idle, and 2.8v with just ignition on i think it is

The engines a ayp, me7.5 ecu ending in 032AA

Havent got vcds at the moment - its on the list of things to get once car is fully built and finished


If you get a diagram of the map sensor, there is 4 wire holes goes similar to this (--- is each pin lol)

---- Earth??
---- No wire, so not used
---- I beleive is signal (reada about 4v on ignition on??)
---- Positive i beleive (this reads 4.7v on mine with ignition on)


The meth controller calculates boost per volt through the wire, controller is fully adjustable, could try and set controller really high and see if that sorts it, but iirc 4v on map sensor is reading near 15-16 psi? If im correct, ill have to find a chart of what voltages mean what

 

[Dan FR]

Autodata is usually pretty good with diagrams and pin outs/voltages and basic ways of checking things, but i cant look until i get home tonight.

VCDS would be good as if you are right with your voltages then the ecu thinks you have 16psi of boost at idle which would be easy to spot.

 

[Adam4D]

Earth wire ok? Signal wire shorted to live? Or sensor failed? Would be my first 3 things to check

4volts on the signal would show a high boost in vcds as the map sensor linearisation goes upwards with voltage. So higher signal wire voltage means higher boost reading.

If you had the map sensor calibration from the ecu you can use excel make a graph to show voltage vs boost

 

[Cammy]

Adam, I get this reading without the sensor connected, my ecu is getting basemapped tomorrow as im running a diferent turbo

I will see what like it is when it comes back, but I wouldn't see it making a difference?

When ECU is back, ill double check the voltages with the new map on it (incase it was the map that was causing this) and set the controller extremely high to see if that stops it coming on all together

And thanks dan I really need to invest in vcds, I have many uses for it, but have never got round to buying it yet due to my engine lol bout time I pulled my finger out ;P

 

[Adam4D]

The map will not give a hardware fault. It could be a default voltage for a disconnected sensor

 

[Cammy]

Even with map sensor connected it still injects with ignition on only

Have tried all wires with no-avail

 

[Dan FR]

What readings do you get with the MAF connected and the engine on/idling (not just ignition?)

Autodata is no help im afraid, all needs diagnostic kit or VCDS to help further.

 

[Cammy]

Well the maf isn't the problem, its the map sensor on the boost pipe

ill double check on the readings when idling, hopefully have my ECU back tomorrow so I could try and see what its coming in at

 

[Dan FR]

I meant MAP (It was late!)