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idle control system fault 1507


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8 replies to this topic

#1 punchycar

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Posted 20 March 2014 - 04:10 PM

I have a 97 Impreza outback sport, 2.2l 5mt.   I keep getting a 1507 code and the odd time a knock bank 1 0325 code.  They will always clear and I now get the 1507 every time I drive the car, it goes into safe mode and runs like crap often but not every time.  It does not seem to matter how the car is driven, as in speeds or distance, it always comes on at some point.  I have searched this topic here and read I think all the threads on the subject that I found might relate to my situation.  

I have cleaned the idle air control valve, it is clean as a whistle and moves freely.  I have checked vacuum lines and replaced a few.  I've disconnected the neutral switch as was suggested in a few threads, though I would love to know how this is related?  

Still have the problem, is there anything else I might try before sourcing a new idle air valve?  Would it be worthwhile to try a used one?



#2 ocei77

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Posted 20 March 2014 - 07:40 PM

In addition to cleaning the IAC, you need to check for vacuum leaks.

Most generally spray carb cleaner and see if engine surges at any point.

If after verifying there are no leaks and you have to replace, go to salvage and get one. Clean it and install. Too pricey for new.

 

O.



#3 Fairtax4me

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Posted 20 March 2014 - 08:05 PM

Check for vacuum leaks like ^ said. Also clean the throttle body bore and throttle plate.

Which switch did you disconnect? The one that matters is on the side of the trans. It's easy to check with an ohmmeter.

#4 punchycar

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Posted 20 March 2014 - 10:43 PM

As I mentioned I have replaced a couple of vacuum lines and have not found any other leaks.  I have not cleaned the throttle body bore yet but will give it a go in the morning.  I disconnected the neutral indicator switch that is on the side of the tranny, I did actually check it when I had the transmission out a couple weeks ago and it tested fine however the insulation on the wires was cracked in a couple places.  Why does the neutral switch have anything to do in this situation?



#5 Darr12

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Posted 21 March 2014 - 01:16 PM

I had the same problem it is the eletrelectrical component on the iac that is most likely shorted.

#6 Fairtax4me

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Posted 21 March 2014 - 05:48 PM

I disconnected the neutral indicator switch that is on the side of the tranny, I did actually check it when I had the transmission out a couple weeks ago and it tested fine however the insulation on the wires was cracked in a couple places. Why does the neutral switch have anything to do in this situation?


The neutral position switch on the trans tells the ECU when the transmission is in gear. This changes the way the ECU responds when you take your foot off the gas pedal depending on if you're coasting in neutral, or engine braking in gear.
If the ECU thinks the trans is in neutral when you take your foot off the gas, it tries to set the engine speed to idle. It will usually hold a high idle for a second or so (long enough to shift gears) to make shifting easier, but then it will settle to normal idle speed.
When the NPS goes bad the ECU may think the trans is in neutral, when it is actually in gear. It tries to set the engine to idle speed, but can't because the drivetrain is turning the engine during engine braking. The ECU will set a code for the Idle control system, thinking the idle valve is stuck, when it can't set the engine to idle speed.

The neutral switch doesn't often fail though, and can be intermittent for a long period before setting a code.
Generally if you have this code its because of some other problem causing the ECU to have to adjust the idle valve as far as it can, and then still need to adjust further in order to set proper idle speed.
Sometimes it is caused by a fault in the idle control motor, but there will usually be other symptoms like rough, low, or high idle, or "hunting" for idle.

#7 punchycar

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Posted 22 March 2014 - 08:48 PM

The neutral position switch on the trans tells the ECU when the transmission is in gear. This changes the way the ECU responds when you take your foot off the gas pedal depending on if you're coasting in neutral, or engine braking in gear.
If the ECU thinks the trans is in neutral when you take your foot off the gas, it tries to set the engine speed to idle. It will usually hold a high idle for a second or so (long enough to shift gears) to make shifting easier, but then it will settle to normal idle speed.
When the NPS goes bad the ECU may think the trans is in neutral, when it is actually in gear. It tries to set the engine to idle speed, but can't because the drivetrain is turning the engine during engine braking. The ECU will set a code for the Idle control system, thinking the idle valve is stuck, when it can't set the engine to idle speed.

The neutral switch doesn't often fail though, and can be intermittent for a long period before setting a code.
Generally if you have this code its because of some other problem causing the ECU to have to adjust the idle valve as far as it can, and then still need to adjust further in order to set proper idle speed.
Sometimes it is caused by a fault in the idle control motor, but there will usually be other symptoms like rough, low, or high idle, or "hunting" for idle.

 

So here is what it is doing now... I have the neutral switch disconnected and cleared the code, drive for twenty minutes just fine and only when I start to downshift for a stop light the cel light comes back on and the car stalls when I come to a stop.  Turn the key off and then start again, runs fine, drive for five minutes and park.   Start up after a few minutes and the cel light is off, drive five minutes, cel comes back on when downshifting for a stop light and stalls when stopped.  Key off and start and will drive fine.  Park for ten minutes, I clear the code and drive back twenty five minutes home where the cel comes back on again when I'm downshifting.  Once the fail safe has been cleared it will idle ok, perhaps a bit low but it never seems to be 'hunting' .

Since I have the neutral switch disconnected, an open situation, is that what we should have when the car is in gear and a closed position when in neutral?  By the description in the post above it really sounds like the neutral switch..... but not if an open circuit is telling the ecu we are in gear?

I did pick up a used idle control motor and may try that out but is does seem curious that this is after changing the transmission and I know that the wires the the neutral switch have cracked insulation....



#8 lmdew

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Posted 22 March 2014 - 09:10 PM

If my memory is correct the N-SW drops the voltage the ECU is sending, 5vdc drops to 0 vdc when the switch is made.  This tells the ECU when you are in gear and when you are Not in gear.

 

The ECU needs to see this switching or it will throw the code.  It expects to see the shift action.  Just disconnecting it will not solve the problem.  

 

I learned this after a Auto to manual swap in a 96 Legacy and it kept doing the same thing you indicated.



#9 punchycar

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Posted 07 April 2014 - 03:32 PM

Turns out that is was the neutral position sensor, put in a new one and has been running like a new one since...... thanks all for the help.






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