high idle/falling rpm solution?!?

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high idle/falling rpm solution?!?

Post by Bassboy3313 on Sun Mar 28, 2010 12:11 pm

Hello. Here is the story ...

I bought the car and found out the IACV was "deleted". The vacuum hose was just disconnected and capped at the end. I would always have to give it gas for a couple seconds when starting it with the engine cold in order for the idle to level out. otherwise it would bog down and die. once it was warm, it would idle around 800-1000 rpm. whenever i let off the accelerator and put it in neutral the idle would fall to about 500 rpm and then come back up.

i finally got to working on the car this weekend and replaced the stock air filter box with a cone filter since i already had an aftermarket intake tube on it. The intake tube had a huge nipple on it that was too big for any hose to fit in so i capped that off with a plug and clamp. the IACV hose was still capped, so i cut the line and T'ed it off the PCV hose going from the valve cover to the intake.

Now, it starts right up every time without having to give it gas for the first couple seconds. Awesome, I think. The new issues however are that it has a very high idle (between 1500 - 2000 rpm) and it still falls down to 500 rpm then back up again whenever i put it in neutral coasting to a stop or just put the clutch in.

I am wondering what could be the cause of the high idle and the falling rpm situations? Do I just need to adjust the idle screw and maybe seafoam the IACV hose to clean it out? Any advice would be great. Thank you!
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Bassboy3313

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Re: high idle/falling rpm solution?!?

Post by stewiefied on Sun Mar 28, 2010 8:38 pm

the iacv opens up when the rpms drop to catch it. i had to take mine off and clean it, then open up the screw a little bit. Since i put the turbo on, mine idles very high also. 1500 to 1800 on cold start and 900 for base idle. i cant get the idle down at all with the screw even with it completely in. but then it dies when i let off the throttle so i opened it until it started raising rpm at idle and left it there. I havent looked into the cause yet, but i think its because the turbo is pushing air into the iacv hose.
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stewiefied

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Re: high idle/falling rpm solution?!?

Post by Bassboy3313 on Sun Mar 28, 2010 9:20 pm

so you basically cleaned the iacv and messed with the idle screw? do you have a ka24de? could you explain how you removed the iacv and how to get to the idle screw? it looks like a bitch to get to them. thanks.
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Bassboy3313

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Re: high idle/falling rpm solution?!?

Post by Dirty Dee on Sun Mar 28, 2010 9:21 pm

a fsm would be beneficial to download
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Re: high idle/falling rpm solution?!?

Post by stewiefied on Sun Mar 28, 2010 9:54 pm

its a turbo kade. all emissions removed so it was pretty easy to to get to. but yes, cleaned it real good. That got rid of most of the dying, then i turned the screw out a little more just to the point that it started raising my already high idle. The more air, the easier it is for the slow, 17 year old iacv to catch the rpm.

fsm, werd...
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Re: high idle/falling rpm solution?!?

Post by Bassboy3313 on Mon Mar 29, 2010 9:35 am

i have teh fsm's. they still dont tell you how to remove it or get to it. ill figure it out i guess. so did it even fix your high idle and falling idle?
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Bassboy3313

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Re: high idle/falling rpm solution?!?

Post by stewiefied on Mon Mar 29, 2010 10:51 am

fixed the falling idle/dying car when i let off the throttle thing. but idk why i cant get my idle below 900. might just be because pressurized air is going into the iac hose instead of atmospheric??
I checked for vacuum leaks and found nothing. let me know how it works.
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Re: high idle/falling rpm solution?!?

Post by Bassboy3313 on Tue Mar 30, 2010 2:24 pm

ok. i messed with the idle screw and it didnt change at all. still high idle and still falls when letting off throttle and in neutral. it doesnt fall as far anymore tho.

I found a thread on nicoclub about the same thing and the guy figured out it was his TPS that was bad. Im gonna test the ohms on my TPS tonight and see if thats my problem.
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Bassboy3313

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Re: high idle/falling rpm solution?!?

Post by stewiefied on Tue Mar 30, 2010 2:50 pm

i think theres also an idle on/off switch in the tps that you have to check.
I was looking at the fsm, and it says to disconnect the o2 sensor, and race the engine to 2000 rpm no load for like 30 sec. then if the rpm doesn't go down, you have a vacuum leak.
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Re: high idle/falling rpm solution?!?

Post by Bassboy3313 on Tue Mar 30, 2010 6:19 pm

hhmmm. ill check that out. i tried to read the TPS plug with my Fluke meter set to ohms and i couldnt get a reading for anything. it just stayed at zero. am i supposed to shove the probes into the slots in the TPS plug? i just touched the probes to them. I dont wanna damage the plug.
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Re: high idle/falling rpm solution?!?

Post by stewiefied on Tue Mar 30, 2010 10:25 pm

you touched the probes to the insulated wire? or the terminals inside the plug? should be touching metal, just making sure.
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Re: high idle/falling rpm solution?!?

Post by fastSRmedic on Wed Mar 31, 2010 1:04 pm

Have you guys been putting the car in "Idle/Timing" mode per the FSM? To change timing and make it stick you have to unplug the TPS with the car running, quickly pulse or "blip" the throttle to 2k-3k RPM and then adjust idle/timing. It sets the ECU to save changes, otherwise it will just adjust itself back to where it was. Idk if that'll help but I thought I'd let you all know.
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Re: high idle/falling rpm solution?!?

Post by Bassboy3313 on Wed Mar 31, 2010 9:17 pm

stewiefied --> i was touching the probes to the terminals inside the plug.

fastSRmedic --> I have not done this. I cant get a reading from the plugs, so i havent been able to set the idle or anything. i will keep this in mind tho.
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Bassboy3313

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Re: high idle/falling rpm solution?!?

Post by stackedclutch on Tue Apr 06, 2010 10:30 pm

i would get everything vacuum related back to stock , then work from there

idle adjustment guide

http://www.240sx.org/faq/articles/throttle_position_sensor_adjustm.htm

also check for vacuum leaks
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