# 1990 240 w/ high idle



## lostmenoggin (Sep 10, 2005)

1990 with a swapped ka24e motor and a 5 speed conversion. Anyways, my problem is when it is in neutral it wants to idle at around 1900-2000 rpms. How can I remedy this? Thanks for any help.


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## zellx2004 (Sep 30, 2004)

lostmenoggin said:


> 1990 with a swapped ka24e motor and a 5 speed conversion. Anyways, my problem is when it is in neutral it wants to idle at around 1900-2000 rpms. How can I remedy this? Thanks for any help.


5-speed conversion? Maybe Throttle sensor? has it always done this, or recently started. Or perhaps it's the idle air control valve.


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## rogoman (Dec 16, 2004)

Check the throttle plate to see if it's sticking; also check the throttle cable for binding.


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## lostmenoggin (Sep 10, 2005)

zellx2004 said:


> 5-speed conversion? Maybe Throttle sensor? has it always done this, or recently started. Or perhaps it's the idle air control valve.


I honestly can't say. Bought the car and had to swap a motor and trans into it. I checked the AAC valve on the back of the upper intake and when I unplugged a connector the idle dropped back down to about 800. Sooooooo, I swapped the whole thing that attaches to the back of the intake from the motor that I took out of the car onto the motor that I swapped into it, and still have the same problem... Do I need to buy a new one, or what?  Thanks again.


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## lostmenoggin (Sep 10, 2005)

AUXILIARY AIR CONTROL (AAC) VALVE (SOLENOID TYPE)
The ECU processes signals received from sensors to determine
the optimum idle speed under varying engine conditions. The ECU senses
engine condition and determines the best idle speed with regards to
coolant temperature and transmission/transaxle gear position. ECU will
then send an electrical on-off signal corresponding to the difference
between actual and optimum idle speed. The AAC solenoid then regulates
the amount of by-passing air by varying the electrical signal’s on
time.

Read this at http://www.240edge.com/manuals/89-90_240sx/e_theory.pdf

When I did my 5 speed swap, I didn't get the trans harness. Maybe that has something to do with my high idle if the AAC is controlled in part by the transmission's gear position? Like it's not getting a signal it needs and is causing it to malfunction... I'm going to get the trans harness and I'm also going to try swapping in the manual ECU.. maybe this will fix it... If anyone has any other advice please post. Thanks.


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