Weird Idle Problem..

[dth0ng69]

Okay I have a d16y7 all stock except I took out the air intake duct, and resonator.
When I first bought the car the idle was pretty low around 300rpm and the car was vibrating a bit. I did a tune-up (Dizzy cap, rotor, spark plugs, and wires, and air filter) and changed the pcv valve. It still didn't really help the low idle.

So I adjusted the Idle set screw behind the throttle body, and that actually helped the shaking and vibration during the idle. I adjusted to what I wanted the idle to be at 650rpm.

I noticed that in the morning when I turn on the car after the is warmed up, my idle didn't stay where I set it at, it was idling around 400-500.
later on in the day when I drive the car I notice that it idles normally like where I want it.

When I turn on my lights during night I notice that it idles pretty high like around 900-950rpm
and just tonight when I got home, I let my car idle when I got to my drive way and turned off the lights for a few minutes it still idled around 800-900rpm

I'm pretty stuck.. Is my IAC messed up? the idle is pretty constant and doesn't move around but it idles pretty random. I never changed the fuel filter, but I doubt that could be the cause of this.... any help/feedback suggestions would be great
thanks for reading.

 

[mylovehx]

pcv valve yo

 

[AliasNeo]

pcv valve yo

he said he changed that....

try cleaning out the IACValve.

remove iac valve spray carb cleaner on it to remove buildup on the filter part and other parts. reinstall and test.

also check the ignition timing. make sure it is set correctly.

 

[mylovehx]

he said he changed that....

try cleaning out the IACValve.

remove iac valve spray carb cleaner on it to remove buildup on the filter part and other parts. reinstall and test.

also check the ignition timing. make sure it is set correctly.

mm im blind. my bad

 

[Esotericimage]

Yep, IAVC i say

 

[Szady]

You want your idle to be at 850rpm, plus or minus 50rpm. 650rpm is way too low for a regular idle. But, clean your IACV to start with. If that dosent fix it, you could have a vacuum leak. Incorrectly set ignition timing wouldnt cause the idle to change like that.

 

[AliasNeo]

You want your idle to be at 850rpm, plus or minus 50rpm. 650rpm is way too low for a regular idle. But, clean your IACV to start with. If that dosent fix it, you could have a vacuum leak. Incorrectly set ignition timing wouldnt cause the idle to change like that.

incorrect ignition too far advanced will cause low idle.

 

[PhntmSk8r]

Adjusting the idle screw without blipping the throttle wont get you an accurate setting either, since the screw basically just lets a pre-determined amount of vacuum bypass the TB plate to keep the car idling.

IE: If it's idling low and you adjust it to idle up to 650rpm, the first time you open the throttle body and close it again (with the car running) it's going to change slightly (100-200rpm) and will idle a little higher.

 

[Szady]

incorrect ignition too far advanced will cause low idle.

Reading > you. I said it wont cause it to change like it is. Yes, it'll cause a low idle. But it wont cause the idle to be 400rpm one time, and the next time to be 800rpm. See what Im saying?

 

[AliasNeo]

Reading > you. I said it wont cause it to change like it is. Yes, it'll cause a low idle. But it wont cause the idle to be 400rpm one time, and the next time to be 800rpm. See what Im saying?

im not going to get in an argument over this but reading does not own me. i simply stated cause low idle. like PhntmSk8r said, idle changes from different variables to whether its user input or outside environment or the engine. moving idle speed is higher than stationary idle speed, so 400 rpm could be stationary while 800 could be moving idle speed. we don't know he just stated he had idle problem. checking ignition timing is a diagnosis to the problem not something to be ignored.

hell a vacuum leak doesnt have to be a vacuum hose disconnected or bad gaskets. it could be a bent valve or damaged valve, a rocker arm resting on the valve if the clearance is too tight(as seen on a vacuum gauge, low vacuum if idle surge). but this doesnt seem to be the likely. i still lean towards cleaning the eacvalve and check ignition timing. all should be checked before changing the adjustment screw on the throttle body.

 

[dth0ng69]

im not going to get in an argument over this but reading does not own me. i simply stated cause low idle. like PhntmSk8r said, idle changes from different variables to whether its user input or outside environment or the engine. moving idle speed is higher than stationary idle speed, so 400 rpm could be stationary while 800 could be moving idle speed. we don't know he just stated he had idle problem. checking ignition timing is a diagnosis to the problem not something to be ignored.

hell a vacuum leak doesnt have to be a vacuum hose disconnected or bad gaskets. it could be a bent valve or damaged valve, a rocker arm resting on the valve if the clearance is too tight(as seen on a vacuum gauge, low vacuum if idle surge). but this doesnt seem to be the likely. i still lean towards cleaning the eacvalve and check ignition timing. all should be checked before changing the adjustment screw on the throttle body.

thanks for the feedback so far, but yeah I'm talking about my stationary idle speed. What I don't understand is my idle changes throughout the day. I mean it doesn't fulcuatate and move around when it idles, It sits correctly when it is idling, but sometimes in the day it would be around 400 RPM, and sometimes it would be 700RPM. (this is both when my car is warmed up) and with my head lights on it would idle around 900-1000 RPM. It isn't consistent where my idle sits at. Should I change my Fuel Filter first or Clean IAC first??

 

[Zzyzxek]

is your engine always the same temperature? that will effect idle.

 

[dth0ng69]

is your engine always the same temperature? that will effect idle.

I'm not sure If its always the same temperature. But heres what a typical day looks like, I turn on the car and drive it for a while the idle is around 400-500rpm
Later on In the day It would be normal, around 700rpm.
When I Turn on the lights at night the idle would be around 900-1000rpm
and sometimes it would be pretty random, the idle doesn't move around it stays pretty constant.
it would go as low as 400 without lights on, and up to 1000 with lights on.