Fluctuating and high Idle

Deranged

New Member
I have a d16y8 and when cold, my idle fluctuates from 500-2000rpm's. And my radiator fan would not come on. I just replaced the coolant temperature sensor, thermostat, and fan switch. This fixed my fan but my idle still fluctuates. I now have no idea what it could be, I have checked my IACV and it looked clean, but I didn't take the hoses off. After my idle stops fluctuating it settles around 1500 and the idle screw is all the way in.

I've inspected for vacuum leaks and didn't find any, and also bled my coolant system after the changing the parts. Anyone have any clues?
 
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Finnish~Racer

The ONLY Finnish-Canadian
Registered VIP
5+ Year Member
take off your iacv and clean it with throttle body cleaner. take off your hoses and check to make sure there not clogged.
 


Deranged

New Member
Alright I'll probably take off the IACV and check those hoses.

No Cell Codes
Manual Transmission
 


Ubajowa

New Member
Have you looked into getting a new PCV? This little bugger helped my idle soooo much it was unbelievable. Well worth the 3 dollar price tag and 10 minutes of work.
 

Deranged

New Member
RonJ said:
Cleaning the IACV would not hurt, but if you have bled the cooling system, I see no need in checking the IACV coolant hoses.



Does the CEL work?



Here is the proper procedure for adjusting the idle speed for your engine:

Click to expand...
I'm honestly not sure if the cell works or not because it has yet to come on for anything. Any way to test it? I will try adjusting the idle using that method, not sure if it will make a difference or not. I am planning on changing the pcv valve when i get a chance, I just don't really see that being the problem but who knows. That is really the last culprit for this problem i can think of so if that's not it I'm completely stumped.
 

RonJ

Banned
Deranged said:
I'm honestly not sure if the cell works or not because it has yet to come on for anything. Any way to test it?
Click to expand...
When you turn the key to ON(II), the CEL should turn on and then off after 2 seconds, if no CEL codes are thrown. If the CEL remains on steady, a code(s) is stored in the ECU.

I will try adjusting the idle using that method, not sure if it will make a difference or not.
Click to expand...
To do the procedure correctly, you need an accurate tachometer. The one in the cluster is not accurate in the rpm range you need to set the idle. I use an Actron scan tool that reads live data. Some other scan tools also have this function. An auto parts store may offer a free rental for the tool if you ask.

I am planning on changing the pcv valve when i get a chance, I just don't really see that being the problem but who knows. That is really the last culprit for this problem i can think of so if that's not it I'm completely stumped.
Click to expand...
The PCV valve would not cause a surging idle unless the PCV hose is leaking or disconnected. There are many other possible causes for a surging idle, such as a vacuum or intake air leak, but start with the items already mentioned.
 

Deranged

New Member
Ok, so I checked and the cel light is working correctly but it is not throwing any codes. I don't have any jackstands on me currently so I can't change the pcv right now, but I like said earlier it probably wouldn't cause this problem. I also checked all visible vacuum lines for breaks/leaks and sprayed throttle body cleaner around the lines and gaskets to see if there was any change in idle and I found no leaks, but a vacuum leak does makes the most sens for the fluctuating and high idle I'm having. Are there any other tests I can do to try and find this problem? I hate to take it to a mechanic and have them charge me for something I could have fixed on my own.
 

Deranged

New Member
Well got the PCV valve changed finally. No change in my problem. Also had a Mechanic check for vacuum leaks and he didn't find any:/ I tried to adjust the idle to bring it down, however when I disconnect the IACV to adjust the idle the proper way the idle does not go down at all, I thought the car was supposed to stall out when you unplug it? Would that suggest a problem with my IACV?
 

Deranged

New Member
Well I took off the IACV again and the hoses, cleaned it all and double checked everything. Also I was told that if you blow into the hose fitting on the bottom of the AICV that air should not come out the other end and if it does, that means its bad. I tried this and air did pass through the valve, so I'm really putting my money on this thing being bad. I'm going to go buy a new one and hopefully not waste my money haha
 

Deranged

New Member
Just changed the IACV....guess I wasted my money because the problem is still there. Infact it has gotten worse in the past couple weeks, now when sitting in traffic my idle will go up and down from 1k to 2k wildly. I have no idea what else to do or what could be causing this.
 

Deranged

New Member
So I guess I just did something I should have done earlier...covered the throttle body with my hand...and guess what. It idled normally, indicating that I have and air intake leak. My question is does anyone one know where I should look for that leak? Would it be in the throttle body somewhere? The gaskets or something?
 

RonJ

Banned
Check the throttle body and intake manifold gaskets and make sure each is torqued to spec.
 

Deranged

New Member
I checked the manifold gaskets as best I could (did not take anything off) and didn't see or hear anything wrong using carb cleaner to test for leaks. Afterwords I put my hand over the intake to see if it would still idle and the dang thing died...just like it should, but the car still runs like crap. So why did the car idle last time I blocked off the intake and this time it dies. Is my ECU shot or something?
 
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