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Guest Message by DevFuse

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MAP sensor and fuel pressure question

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3 replies to this topic

#1 velorossa


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Posted 15 March 2009 - 10:39 PM

I have a 96 legacy 2.2L 5spd
First of all there is 3 wires going to the MAP (or in subaru terms "boost sensor"). A red a green and a red/yellow. The red/yellow I think is the supply voltage since it also connects to the MAF and the TPS. But both the green and the red connect directly to the ECU. Does anyone know which one the ground is and which one gives the return voltage to the ECU?
Also I'm thinking that my fuel pressure regulator is going bad. Car seems to low idle when warming up for about 20 minutes ( the low idle that is) and shakes the car. It doesn't stutter when accelerating and the spark plugs look okay. If I hold the throttle down just a tad to jump up the idle it runs better. It usually low idles when coming to a stop and after a few seconds seems to go back up again. I used fuel injection cleaner but to no avail.
So my question is I seen a universal fuel pressure regulator with pressure gauge and adjustment ( says it fits subaru) for less than $40 on ebay. A stock one is way more. Would one of the aftermarket things work on my subaru?

#2 Cougar


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Posted 15 March 2009 - 11:36 PM

Looking at some data it shows the red/yel ties also to the blk wire of the TPS so I would say that is the return side of the circuit. The red wire may be a 5 volt reference power supply lead. I don't think it ties to 12 volts.

#3 Gloyale


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Posted 16 March 2009 - 11:02 AM

If you're fuel pressure was low, it would show under load at high RPM, not at idle.

I wouldn't mess with that before having the pressure tested. otherwise you are likely wasting money on parts.

I am going to say you have a sticky IAC

#4 velorossa


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Posted 16 March 2009 - 06:13 PM

I thought that the TPS and the MAP would want to give the ECU different readings. If they were in series the ecu wouldn't be able to tell the difference of which one is which. But if the red/yellow is the 5v supply then they could tell the difference b/c it would be in parallel (supply that is) and each component could give the ECU a different signal wire ( being the red wire going directly to the ECU).Unless that's the way subaru wants it where both of them read together as one. Is that the case?
Where is the location on the IAC? Maybe I can try cleaning it up.
Thanks guys,

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