Rough idle on warm engine
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Honda-Tech Member
Joined: Dec 2020
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Rough idle on warm engine
Hello there, I'm new to this site!
So I have a 2001 Civic with the D16V1 engine.
The idle speed goes up and down from about 1k to 2k RPM, mostly or only when the engine is hot.
Weirdly enough, turning the hot engine off and on will result in steady 1k RPM idle. As soon as I touch the throttle it starts bouncing up and down again.
Sometimes it will be stuck to 2k or lower to 1k and stay there after a while.
I have removed the throttle body and IACV and cleaned them with throttle botty cleaner with no effect. I also disconnected the IACV which resulted in a really bad running engine.
I then disconnected the MAP and the idle problem was gone. It didn't behave completely normal, but close enough.
Does that even mean anything? I tried cleaning the MAP but the rusty screw stripped out badly so I couldn't remove it.
I also made sure there is nothing clogging up the air cleaner/resonater by running the engine without the air cleaner cover.
Anybody has an idea on what to do next?
So I have a 2001 Civic with the D16V1 engine.
The idle speed goes up and down from about 1k to 2k RPM, mostly or only when the engine is hot.
Weirdly enough, turning the hot engine off and on will result in steady 1k RPM idle. As soon as I touch the throttle it starts bouncing up and down again.
Sometimes it will be stuck to 2k or lower to 1k and stay there after a while.
I have removed the throttle body and IACV and cleaned them with throttle botty cleaner with no effect. I also disconnected the IACV which resulted in a really bad running engine.
I then disconnected the MAP and the idle problem was gone. It didn't behave completely normal, but close enough.
Does that even mean anything? I tried cleaning the MAP but the rusty screw stripped out badly so I couldn't remove it.
I also made sure there is nothing clogging up the air cleaner/resonater by running the engine without the air cleaner cover.
Anybody has an idea on what to do next?
Last edited by knipsi22; Dec 20, 2020 at 12:41 PM.
Thread Starter
Honda-Tech Member
Joined: Dec 2020
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Re: Rough idle on warm engine
Some more info:
No engine codes, no cel.
My chinese OBDII Reader shows: fuel system status: open loop or closed loop.
That display changes correlating to the change in idle speed.
I don't even know what that meens.
Also the MAP Reading correlates to the idle speed.
Throttle postion sensor behaves as expected. Only weird thing: The min value when I don't press the throttle is 9% not 0%. I remember that was the case though before the problem was there.
No engine codes, no cel.
My chinese OBDII Reader shows: fuel system status: open loop or closed loop.
That display changes correlating to the change in idle speed.
I don't even know what that meens.
Also the MAP Reading correlates to the idle speed.
Throttle postion sensor behaves as expected. Only weird thing: The min value when I don't press the throttle is 9% not 0%. I remember that was the case though before the problem was there.
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Joined: May 2021
Posts: 1
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Re: Rough idle on warm engine
Hey man,
I have pretty much same issue (same car and engine) as you. I have tried to clean IACV as well as I could. Also TB and MAP but no effect. I also tried the ecu idle relearn process... No effect. No fault codes and just passed emissions test with no issues. @knipsi22 did you manage to resolve your idle issue?
Just to clarify. Idle goes near 2k when engine is warm... When I stop the car there is a little fluctuation and the after a moment the idle goes back to normal under 1k and stays there. Also car does not stutter or hesitate under acceleration.
Any ideas?
I have pretty much same issue (same car and engine) as you. I have tried to clean IACV as well as I could. Also TB and MAP but no effect. I also tried the ecu idle relearn process... No effect. No fault codes and just passed emissions test with no issues. @knipsi22 did you manage to resolve your idle issue?
Just to clarify. Idle goes near 2k when engine is warm... When I stop the car there is a little fluctuation and the after a moment the idle goes back to normal under 1k and stays there. Also car does not stutter or hesitate under acceleration.
Any ideas?
Honda-Tech Member
Joined: Apr 2021
Posts: 17
Likes: 0
Re: Rough idle on warm engine
I was driving around for ~3 hours and after Idling for 10 mins, I noticed that the ipm would bump from normal, to up, to down, to normal... weird. I just bought the car a week ago. No CEL or anything.
After I changed the valve cover gasket and put in new spark plugs, the idle remained constant and everything is A-Okay
After I changed the valve cover gasket and put in new spark plugs, the idle remained constant and everything is A-Okay
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