Idle Speed Fluctuates & Many Possible Causes (Diagnose & Fix)

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Idle Speed Fluctuates & Many Possible Causes / Ways to Fix It.
This is for Honda Accord 2003-2011.
There are many reasons your Honda's idle speed fluctuates. I had to perform many different tests. I have success and failures. But eventually I fixed the problem or problems. By watching my video, hope it can save you the time and money.
cartrek.com/idle-speed-fluctua...
update 1: After I replaced the coolant see • How to Replace Coolant... , it run perfectly for a week until the problem came back see • Solution For Collapsed... . I then fixed the radiator cap problem, it run perfectly for another week.
update 2: after the previous fix, a week later, the problem came back again. Then
I cleaned the throttle & IAC valve, watch • Clean Idle Air Control...
the car run perfectly again.
Since there are many components on either the fluid or air paths, you can watch this video and first try the easy and free ways to test to see if a particular component is causing the problem. After those free tests, you can spend some money on those components that you have to perform your regular maintenance anyway, in this way, you are not really spending money for nothing.
This way at least you eliminate a lot of possibilities so that you can focus on other hard problems. After you have done your easy testing, post your results here on the comment section, which one did you test? How was the result? Which one you could not test, we will show you some DIY tools to help diagnose other components.
Index
0:00 idles up and down
0:33 leak on intake of mixture of air or fuel
0:53 change of air & fuel mixture leads to revolution up
1:13 use your own eye sensors to see leak
1:34 hissing sound
2:08 use car's sensor: carburetor cleaner or propane
3:39 service bulletin software upgrade
4:13 code reader
4:59 code P0507 means Idle Control System RPM High
5:31 possible cool start due to weak battery?
5:52 possible timing and fuel pressure?
6:16 check other simple things first scheduled maintenance
6:36 coolant replacement affects sensor input
7:00 after coolant flush makes sure to bleed air out
7:20 idle control unit needs time to re-learn control of idling
7:45 flushing coolant helped , but still fluctuate a little
8:32 lucky without doing anything, must be idle control unit re-learn kicked in
8:53 cold start 1500 RPM to 800 RPM warm normal
9:39 luck did not last, idle up and down again
10:15 notice collapsed coolant hose
12:26 re-train software PCM to re-learn idle control
12:49 do PCM re-learn if replace battery, replace PCM or cleaning intake
13:23 PCM re-learn process step 1
13:43 PCM step 2 and step 3
14:06 step 4: run 3000 RPM wait radiator fans kick in
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