Sr20det Idle Loop when cold - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

240msh · 01-07-2020, 11:41 AM

I daily drive my car, basically everyday, and the only time this happens is during winter when its cold outside. My car will idle from 1200 rpm, to about 2k rpms then go back to 1200 then back to 2k over and over and over again. Ive swapped IACV but maybe I got a bad one again? Only other thing I could think of is me not running coolant lines to throttle body but ive never heard of anyone having this issue because of that. Maybe because of my colder thermostat and ecu is trippn? Car runs SOLID. Just this issue when cold.

Any info helps, thank you

I have a video if anyone wants to hear lol

This is the 3rd winter in a row with this going on and im over it

Kingtal0n · 01-07-2020, 01:44 PM

coolant in the throttle body brings down idle

it's got some kinda wax element

read the fsm

240msh · 01-07-2020, 02:45 PM

yeah I know that, but everyone on forums is saying they've never had issues when bypassing them. they say its mostly for places where it gets super cold. (im in las vegas)

its not that it just sits there and idles high either, it literally loops from 1200-2000 when the temp is cold outside, car can be warmed up and itll still do it (by warm I mean 145+)

ive tried capping them off too, for throttle body and iacv coolant lines thinking maybe cold air is making it act all weird, no change

mechanicalmoron · 01-07-2020, 08:13 PM

Quote:

Originally Posted by 240msh

yeah I know that, but everyone on forums is saying they've never had issues when bypassing them. they say its mostly for places where it gets super cold. (im in las vegas)

its not that it just sits there and idles high either, it literally loops from 1200-2000 when the temp is cold outside, car can be warmed up and itll still do it (by warm I mean 145+)

ive tried capping them off too, for throttle body and iacv coolant lines thinking maybe cold air is making it act all weird, no change

This is a textbook symptom of a bad thermostatic high idle valve. Or one that some dipshit bypassed.

At least, on a honda. I don't know about an SR.

Kingtal0n · 01-09-2020, 12:29 PM

Hah.

Well here is what i recommend if you don't wana hook up the coolant
Install a ball valve (yes from home depot) between the IACV and the cold pipe.
then simply regulate the idle down as low as you want... Assuming there are no vacuum leaks.

Remember that airflow = idle speed.
So if you have high idle speed its getting too much airflow.
It can be getting in say, behind the intake manifold or something.
So do a pressure test is what I am saying. then add the ball valve if necessary I guess.
I got the idea of the home depot ball valve from my father who installed one on his sr20 without me knowing.
I started it cold and it idled low and smooth, whereas they usually rocket up in idle speed when you first start "cold" (florida 80*F)
I was like oh shit something is wrong! but then I saw the home depot part and /facepalm but you know what, it fuckin works!

*brndck* · 01-14-2020, 03:47 PM

step 1, check for vacuum leaks.
step 2, repeat step 1 cuz it sounds like you have a vacuum leak.

240msh · 01-15-2020, 12:00 PM

Quote:

Originally Posted by brndck

step 1, check for vacuum leaks.
step 2, repeat step 1 cuz it sounds like you have a vacuum leak.

no leaks, ive checked 1000 times, swapped through intercoolers and pipping, gaskets, iacv's everything no signs of any leaks. hookd up a compressor with a gauge to intake no sounds of any air leaking through either

Quote:

Originally Posted by Kingtal0n

Hah.

Well here is what i recommend if you don't wana hook up the coolant
Install a ball valve (yes from home depot) between the IACV and the cold pipe.
then simply regulate the idle down as low as you want... Assuming there are no vacuum leaks.

Remember that airflow = idle speed.
So if you have high idle speed its getting too much airflow.
It can be getting in say, behind the intake manifold or something.
So do a pressure test is what I am saying. then add the ball valve if necessary I guess.
I got the idea of the home depot ball valve from my father who installed one on his sr20 without me knowing.
I started it cold and it idled low and smooth, whereas they usually rocket up in idle speed when you first start "cold" (florida 80*F)
I was like oh shit something is wrong! but then I saw the home depot part and /facepalm but you know what, it fuckin works!

that's interesting lol, if I cant find any other fix ill def give it a shot cause this is super annoying lmao

*brndck* · 01-15-2020, 02:38 PM

have you cleaned out your IACV?

perhaps its sticking, and cant operate smoothly.

i fill em with electronics cleaner or carb spray, then us a power probe to actuate it, and typically they have a ton of buildup in them. Ive seen ones that could barely click open because they had so much crap in em.

are you still running a stock ecu or aftermarket?

240msh · 01-15-2020, 04:27 PM

Quote:

Originally Posted by brndck

have you cleaned out your IACV?

perhaps its sticking, and cant operate smoothly.

i fill em with electronics cleaner or carb spray, then us a power probe to actuate it, and typically they have a ton of buildup in them. Ive seen ones that could barely click open because they had so much crap in em.

are you still running a stock ecu or aftermarket?

I believe I cleaned it a lonngggg time ago but ill try that method w power probe. Ill let you know if it works! Stock ecu

*TheRealSy90* · 01-15-2020, 05:23 PM

Especially if you're running a "greddy" intake manifold that puts the IACV on the bottom, the tend to fill up with oily residue more quickly.

Have you made sure that your throttle plate is FULLY closed at idle? A lot of people make the mistake of adjusting the throttle plate stop when doing idle adjustment. It should be fully closed and the IACV provides all idle air...

240msh · 01-17-2020, 09:55 AM

Quote:

Originally Posted by TheRealSy90

Especially if you're running a "greddy" intake manifold that puts the IACV on the bottom, the tend to fill up with oily residue more quickly.

Have you made sure that your throttle plate is FULLY closed at idle? A lot of people make the mistake of adjusting the throttle plate stop when doing idle adjustment. It should be fully closed and the IACV provides all idle air...

ahhh that makes sense, I use the stock manifold so that should be good. Cleaned it out seems like it helped a little but not 100%.

I did but it was a long ass time ago, ill give that a look I might have it slightly open then +iacv its just getting a lot of air flow.. hopefully that's it and I just overlooked something super simple lol

01-07-2020, 11:41 AM	#1
240msh Zilvia Member Join Date: Oct 2016 Location: Las Vegas Age: 22 Posts: 234 Trader Rating: (1) Feedback Score: 1 reviews	Sr20det Idle Loop when cold I daily drive my car, basically everyday, and the only time this happens is during winter when its cold outside. My car will idle from 1200 rpm, to about 2k rpms then go back to 1200 then back to 2k over and over and over again. Ive swapped IACV but maybe I got a bad one again? Only other thing I could think of is me not running coolant lines to throttle body but ive never heard of anyone having this issue because of that. Maybe because of my colder thermostat and ecu is trippn? Car runs SOLID. Just this issue when cold. Any info helps, thank you I have a video if anyone wants to hear lol This is the 3rd winter in a row with this going on and im over it __________________ IG @Michayyl

01-07-2020, 02:45 PM	#3
240msh Zilvia Member Join Date: Oct 2016 Location: Las Vegas Age: 22 Posts: 234 Trader Rating: (1) Feedback Score: 1 reviews	yeah I know that, but everyone on forums is saying they've never had issues when bypassing them. they say its mostly for places where it gets super cold. (im in las vegas) its not that it just sits there and idles high either, it literally loops from 1200-2000 when the temp is cold outside, car can be warmed up and itll still do it (by warm I mean 145+) ive tried capping them off too, for throttle body and iacv coolant lines thinking maybe cold air is making it act all weird, no change __________________ IG @Michayyl

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

01-07-2020, 01:44 PM	#2
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 38 Posts: 4,649 Trader Rating: (17) Feedback Score: 17 reviews	coolant in the throttle body brings down idle it's got some kinda wax element read the fsm

01-09-2020, 12:29 PM	#5
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 38 Posts: 4,649 Trader Rating: (17) Feedback Score: 17 reviews	Hah. Well here is what i recommend if you don't wana hook up the coolant Install a ball valve (yes from home depot) between the IACV and the cold pipe. then simply regulate the idle down as low as you want... Assuming there are no vacuum leaks. Remember that airflow = idle speed. So if you have high idle speed its getting too much airflow. It can be getting in say, behind the intake manifold or something. So do a pressure test is what I am saying. then add the ball valve if necessary I guess. I got the idea of the home depot ball valve from my father who installed one on his sr20 without me knowing. I started it cold and it idled low and smooth, whereas they usually rocket up in idle speed when you first start "cold" (florida 80*F) I was like oh shit something is wrong! but then I saw the home depot part and /facepalm but you know what, it fuckin works!