KA24E High Idle after warm up. SOHC Genius' look here

[firefighter573]

My SOHC KA idles high at around 2000 rpm after warm up.

I cleaned my IACV and the issue is still apparent.
I checked all the vacuum lines and nothing is out of order.
I even turned the idle set screw all the way in on the IACV and no drastic change happened.

When I turn the A/C on the idle drops a little bit.

Am I missing something here?

[Mishkin_707]

Is it running a little rich? Disconnect the CTS and see if idle goes down, CTS is coolant temp sensor, disconnect the red 2 pin one not the black single pin

[firefighter573]

YES it is running rich, will disconnect the CTS and report back

[firefighter573]

And i recall the Temp gauge needle likes to dance up to normal operating temp, then it stays in its place

[firefighter573]

Looked on the FSM and the only temp sensor i was able to come across was the Engine temp sensor (Red) that is attached on the top of the intake manifold near the 1st runner. To troubleshoot it the FSM said to start the car without the sensor connected. Thus here is what i did...

(sensor connected) - started the car, immediate COLD idle was 1100 rpm...as soon as the car started to warm up, the idle speed rocketed to 2000 rpm. I shut the car off.

(sensor disconnected) - started the car, immediate WARM idle was at 800 rpm, then rose to 1300 rpm fairly quickly. STILL MUCH LOWER THAN THE NORMAL 2000 rpm. I shut the car off.

(sensor connected) - started the car, immediate WARM idle was at 2000 rpm again and holding it tight.

[RedTopKA-T]

When you adjusted the idle screw did you disconnect the tps first? I had a similar problem but not as high of an idle ,and I tried to adjust the screw but nothing really changed so I cleaned the iacv, pcv, air regulator,and coolant temp sensor and i still had the problem,I did a little research and found out that you have to disconnect the tps first then start the car and set the idle to 600rpm shut the car off and connect the tps the start it up and it should be good. ...that solved my idle problems its worth a shot.
And the single black plug he is talking about is right next to the red one and its for the dash temp gauge ,I have mine hard wired and it works fine

[Mishkin_707]

What redTopKa-T said ...beat me to it. Have you done anything prior to it acting up like that? Have you checked the throttle pedal? Maybe it's sticking

[firefighter573]

I had a similar problem but not as high of an idle ,and I tried to adjust the screw but nothing really changed so I cleaned the iacv, pcv, air regulator,and coolant temp sensor and i still had the problem,I did a little research and found out that you have to disconnect the tps first then start the car and set the idle to 600rpm shut the car off and connect the tps the start it up and it should be good

I just tried this.

I unplugged the TPS, started the car, turned the idle set screw in and the rpms wouldn't drop below 1300 rpm even with the screw all the way in. So Shut the car off, reconnected the TPS...Same issue lol

[firefighter573]

I haven't checked the acceleration pedal because I want to say that would feel "OBVIOUS"

[firefighter573]

Here's a link to the idle issue


http://i923.photobucket.com/albums/ad80/firefighter573/91a55cef.mp4

[Mishkin_707]

Do you have any kind of mods? Intake/exhaust/header?

[firefighter573]

Do you have any kind of mods? Intake/exhaust/header?

No. COMPLETELY STOCK EVERYTHING

[firefighter573]

Here's another link to my recent finding when I was coming home from work

http://i923.photobucket.com/albums/ad80/firefighter573/46726965.mp4

[KiLLeR2001]

Check your ECU for codes. Check resistance on the CTS, clean MAF.

[h2v7]

you got a small little tear in your intake boot thingy watttch it

[keepitslideways]

Having the same issue on my friend's car. Idle comes down substantially after disconnecting the temp sensor. Looking for possible fixes. Thanks!

[firefighter573]

Check resistance on the CTS

I hate to be such a damn noob, I'm looking all over through the FSM and can't find any values and or understand exactly how to check it..

How do I check it? This is the meter I have

http://i923.photobucket.com/albums/ad80/firefighter573/2708d025.jpg

I'm still puzzled as to why the car while Idle high under 15mph, and anywhere above that it's normal.

[KiLLeR2001]

Switch it to 20K OHM, pull off the harness plug and test both leads on the sensor itself. The lower the number the hotter the ECU interprets water temperature.

Temperature - Value:

68F: 2.1 - 2.9
122F: 0.68 - 1.00
176F: 0.30 - 0.33

[firefighter573]

I can't get a steady straight reading. It jumps in between 2.0-3.0 at cold, and at operating temp its anywhere between 11.10-15.75, doesn't stay still.

And here is a link showing my OBD trouble codes, I don't understand how to read them.

Thanks again for ALL of yalls help and guidance!!

http://i923.photobucket.com/albums/ad80/firefighter573/4787c177.mp4

[KiLLeR2001]

Your sensor is bad, resistance numbers should be very low at normal operating temp. I have a brand new sensor still in the box and it reads 1.81 at room temperature.

[firefighter573]

PM'd, still looking for tips! I'm really onto this issue

[firefighter573]

Swinging by Autozone today to get a replacement CTS.

will report back after installation

[firefighter573]

Coolent Temp Sensor changed, Resistance readings were within tolerance. Old sensor turned out to be bad, however.

HIGH IDLE REMAINS...

[KiLLeR2001]

At this point, you need to check the ECU for codes.

[firefighter573]

And here is a link showing my OBD trouble codes, I don't understand how to read them.

Thanks again for ALL of yalls help and guidance!!

http://i923.photobucket.com/albums/ad80/firefighter573/4787c177.mp4

I dont understand how to count the blinks =/
Inquire in Video link above
Im assuming its a code 23, 24, and 25

[KiLLeR2001]

23 - Idle Switch
24 - Throttle Valve Switch
25 - Idle Speed Control Valve

Check your IACV and make sure everything is plugged in... lol

[firefighter573]

Already been checked.

I cleaned the IACV thoroughly, even replaced it with another one, plugged everything up, and still the same issue, this blows, my soon to be next step is trying another ECU

[firefighter573]

Should my idle change if I unplug it while the car is running?

[KiLLeR2001]

Should my idle change if I unplug it while the car is running?

Most definitely. You may want to inspect the wires thoroughly if everything is plugged in correctly. Check your grounds as well, make sure the chassis and engine block are grounded well.

[firefighter573]

Most definitely. You may want to inspect the wires thoroughly if everything is plugged in correctly. Check your grounds as well, make sure the chassis and engine block are grounded well.

I will definately check these, would I be able to check the continuity in the harness plugs themselves if to determine if the plug is good or bad?

Before I first removed the IACV i removed the plugs and there was no change in idle.

[KiLLeR2001]

If you want to check continuity you would need to check from ECU harness plug to the IACV plug.

You most likely have one of the following problems:

- A break in a wire somewhere / damaged harness / ECU plug not fully seated etc
- IACV is completely non-functional
- ECU has an issue in the IACV circuit

[firefighter573]

I have put 2 different IACV (Completely clean) in and still have the issue. - Ruled out

I will remove the ECU, crack it open and look inside to see any visual defects.

Tomorrow I will inspect the wires and grounds to ensure everything is proper.

[KiLLeR2001]

You can find all the ground wire locations in the FSM.

http://www.nicoclub.com/FSM/240sx/91-94/EL.pdf

Page 90 on down has the harness layout with various grounds.

[firefighter573]

Would the SOHC FSM be any different than the DOHC FSM?

Thanks for the added research!

Heres the SOHC FSM for other people digging for answers:

http://www.nicoclub.com/FSM/240sx/1989/1989.pdf

[firefighter573]

Cracked open the ECU, FRESH AS FFUUUUUUUU.

Everything appears to be in order, no faults, burns, anything of the sort. (shook the ECU first before opening it to listen for broken internals)

Onto checking the harness and grounds

[lbogkush]

i also had this problem when i first got my car SOHC89
changing idle isn't that hard idk if u tried this yet but it worked for me
follow this link it also apply for SOHC http://zilvia.net/f/s-chassis/395413-idle-adjust-procedures-ka24de-240sx-pictures.html
EXAMPLE:
make sure car is warmed up drive whatever just make sure its warm up
shut car off open hood take tps plug off
(first picture of tps in the link is right but pull out the gray plug next to the screw with the red black yellow wire easier)
go back into car then start and let it idle for 10sec to where ever it idles to then
adjust the idle screw (second pic is correct)
turn left to rise idle right to lower idle
i just lower idle all the way then worked it up to 700RPM stock idle for manual
once it at the idle u want shut car off first take the key out of ignition THEN go plug the tps back in MAKE SURE or it will throw CL
after u shut car off then plug tps back in
start it back up and see if it idle where u wanted

if you did this right and idle doesnt go down it might be because you move your dizzy moving dizzy bring idle down i heard but i never tried it i heard it mess up timing try putting dizzy back to the right angle if that doesnt work sry
idk something u can do maybe it might help

[siksyndicate]

i also had this problem when i first got my car SOHC89
changing idle isn't that hard idk if u tried this yet but it worked for me
follow this link it also apply for SOHC http://zilvia.net/f/s-chassis/395413-idle-adjust-procedures-ka24de-240sx-pictures.html
EXAMPLE:
make sure car is warmed up drive whatever just make sure its warm up
shut car off open hood take tps plug off
(first picture of tps in the link is right but pull out the gray plug next to the screw with the red black yellow wire easier)
go back into car then start and let it idle for 10sec to where ever it idles to then
adjust the idle screw (second pic is correct)
turn left to rise idle right to lower idle
i just lower idle all the way then worked it up to 700RPM stock idle for manual
once it at the idle u want shut car off first take the key out of ignition THEN go plug the tps back in MAKE SURE or it will throw CL
after u shut car off then plug tps back in
start it back up and see if it idle where u wanted

if you did this right and idle doesnt go down it might be because you move your dizzy moving dizzy bring idle down i heard but i never tried it i heard it mess up timing try putting dizzy back to the right angle if that doesnt work sry
idk something u can do maybe it might help

I think you're the only one who asked about his timing. Is it loose? or way advanced?

[firefighter573]

Why would timing be attached to any issue that's going on here?

The Ignition timing is dead center,

The car idles high only under 15 mph, it's something electronically controlled that is causing the issue.

However, thanks to a friend I got my hands on a nice Snap-On Solus scanner and the issues became present!
4 codes found

http://i923.photobucket.com/albums/ad80/firefighter573/c2864f6b.jpg

[firefighter573]

HIGH IDLE IS GONE!
ISSUE?? One of something which was replaced below.
Heres the story:
As i was driving the car, somehow my LF tire picked up a rock, and let go of it right up into the engine bay landing directly into the ignition coil, destroying it, and all the spark plugs fouled instantly...sounds fucking stupid right? Pics or BS? look below.
http://i923.photobucket.com/albums/ad80/firefighter573/cd01207e.jpg
http://i923.photobucket.com/albums/ad80/firefighter573/66c6e561.jpg
http://i923.photobucket.com/albums/ad80/firefighter573/0fd82a28.jpg
So, I went and purchased a new ignition coil, plugs, and wires. Installed everything, started the car, and took it for a spin, kept driving it and then realized..."Its not idling high!?". THE HIGH IDLE IS GONE, Idling at 1000 rpm now. So where did the issue come from?
My assumption would be the aftermarket Accell Race wires, would the rather large wires with a stock ignition coil cause this?
http://i923.photobucket.com/albums/ad80/firefighter573/e3ee50d3.jpg

[Mishkin_707]

That's a 1 in a 1,000,000 shot.....lol glad you got it figured out

[KiLLeR2001]

1000 is still a high idle.

[Mishkin_707]

Maybe now he just has to adjust his idle