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Hello
I had my Honda Civic 96 sitting for about 2 years. Got a new battery, got it to crank and now it drives fine except for idle issues, once car gets warmed up. Its been about 4 months, but I only drive it in my neighborhood from time to time. I tried resetting ecu pulling back up 7.5 fuse out but it didnt fix the issue. I did pull the fuse when the engine was cold tho.

After I start my car engine revs at a constant 1,500 rpm, about 5 min later the car goes from about 1,100 rpms to 1,900 rmps. It only revs like this in Park and Neutral, once I put it in drive there are no problems.

Hooked up my OBD scanner and it didnt throw any codes. I did a live monitor test which are in the videos below (the weird sound in the background is rain)

Anyone know what could be causing these problems, and how I can fix them.

 
Rep Power: 519

Vacuum leak, or IAC is stuck open?

 
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are those the first things i should check? you dont think its caused by air in the cooling system do you?

 
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are those the first things i should check? you dont think its caused by air in the cooling system do you?

 
Rep Power: 519

Well it sounds like you are already aware that trapped air can cause it, therefore you have already checked filled and burped the cooling system of trapped air.....yes?




Once I know what is causing the issue, then I can track down why it's causing the issue.


Is the IAC extremely hot after the engine is all warmed up?

 
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lol, havnt done anything yet. i will burp the system tomorrow, and double check the vacuum hose. after that i guess ill fiddle with the iac, what temperature would be extremely hot?

 
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I burped the system, didnt change anything. I have to let the car cool down before i check for vacuum leaks. Is it okay if i use wd-40 on a cold engine to check for idle changes so i know if there is a leak? and where do i check for leaks and where should i avoid them? i also dont know where the iacv is. sorry im pretty noob at this.

 
Rep Power: 519

Remove intake air tube (or filter lid, whatever it has) from throttle body.
Locate the open ports in the side of the throttle body housing (inside)
With the engine warmed up and surging, use your fingers to block each open port, see if the idle drops to normal.

Random goggle image:




Extremely hot means the 180*F+ coolant temperature, the IAC/FITV has to have good coolant flow.