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RPM Stumbles after revving

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Old 07-31-2018, 04:31 AM
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Default RPM Stumbles after revving

I think this subject has been broached over and over again but nothing I have read so far has helped me cure my problem. So here goes......
Rev the engine and when it returns to idle the engine sometimes shudders as the revs drop to around 60r7k for a second. Same thing happens when I pull away without giving it plenty of revs.

I have set the TPS to as near to 6% as possible (5.9%) I have thoroughly stripped and cleaned the IAC valve. I have replaces the MAP sensor and thoroughly
cleaned the throttle body and adjusted the throttle cable. I have re-learned the ECU god knows how many times and my code reader shows no fault codes. Both O2 sensors read between 0-1volt. The car has 54,000 miles and otherwise runs fine, on the cam and off (VTEC). Valve clearances also double checked. It has done this since I purchased it 3 years ago and I would really love to finally sort out the problem once and for all. It seems odd that it does not do it every time the engine returns to idle. Please help!

https://www.youtube.com/watch?v=4dd_...ature=youtu.be

Last edited by Snakecharmer; 08-03-2018 at 04:25 AM. Reason: add video
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Old 07-31-2018, 01:03 PM
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The most common culprit is the idle valve, which you say you cleaned, did you split the two halves and ensure the internal roller spins freely ?
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Old 07-31-2018, 01:41 PM
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Cant see link you added +ECM/ECU is supposed to dip with the blip of pedal, timing advance /retard &learn for close loop ect aircon & fans on/of & engine loads ect.
That's how you know its working correctly.3-400 rpm iirc then corrects to normal 4-6 seconds.
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Old 07-31-2018, 10:18 PM
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A flat/ageing battery can cause this. I had similar experience with mine. Idle was very lumpy until I switched out the battery.
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Old 08-01-2018, 02:19 AM
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Fully stripped the idle valve and bled the system. Battery is brand spankers. I have just ordered a new set of plugs in case the ilrridium ones fitted have failed. Is there any chance a bad knock sensor could cause this?
the video was uploaded to flicker. I will try again with youtube.

thanks for the responses.
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Old 08-01-2018, 03:54 AM
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My car does the very same thing - and i was unable to find a cure.

I have a sneaking suspicion this is one of those quirks that effects many S2Ks and can have you chasing your tail...
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Old 08-01-2018, 04:20 AM
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I have heard this said, having trolled through dozens of blogs. I don't believe it would have left the factory like this so there must be a fix. If I find out I will definitely post the cure.
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Old 08-02-2018, 12:59 AM
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I had this exact same thing and did the following:
Valve clearance
Denso MAP sensor from civic
Denso Coil packs
New Spark plugs
TB clean
IACV clean
All these did subdue it, but it was still there.
The last thing I changed was both O2 sensors for Denso (OEM) ones from RokAuto. This as practically cured the issue. I only now see it on hot days, which I think is actually heat soak on my AEM CAI.
Finally an ECU relearn.
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Old 08-03-2018, 04:25 AM
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Just noticed on my video that the bottom line on the live data screen shows Short Term Fuel Trim and I am learning about this and Long Term fuel trim here....
Thought this guy is very interesting Even his video comes up on here...... Wheras mine https://www.youtube.com/watch?v=4dd_V0vkKYw&feature=youtu.be

Last edited by Snakecharmer; 08-03-2018 at 04:27 AM.
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Old 08-03-2018, 06:08 AM
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Does your car exhibit the issue when fully up to operating temp? I checked mine after a long drive and it didn't seem to have the issue.
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