Shudders after returning to idle
10-12-2018, 12:41 PM
#1
Thread Starter
Shudders after returning to idle
I know there’s been several threads on this; it seems like several people have attempted all of what I’ve done and still haven’t remedied the issue.
After revving the car or even lightly blipping the throttle the revs drop down like normal, but dip to around 500 or so for a second causing a shudder/stutter, and then return to normal warm idle rpms. Car drives great aside from that; vtec engages fine, no hesitation, no problems in the upper rpm range.
Did a recent tune-up:
New factory spec NGK plugs (.039, .041, .042, .042)
New OEM Map sensor with “updated” zip tie holder
New OEM PCV valve
Billman’s TCT
Cleaned IACV completely
ECU relearned
The only thing I didn’t do is clean the throttle body and MAP channel out. Last time I had the intake off I noticed very little carbon build-up. IACV wasn’t that bad either as the car only has 53k miles on it. Oil level is full and fresh (lol), and fresh 93. I’m thinking try cleaning the throttle body/map channel anyway? Perhaps a valve adjustment? Quickly running out of ideas, or is this common behavior?
After revving the car or even lightly blipping the throttle the revs drop down like normal, but dip to around 500 or so for a second causing a shudder/stutter, and then return to normal warm idle rpms. Car drives great aside from that; vtec engages fine, no hesitation, no problems in the upper rpm range.
Did a recent tune-up:
New factory spec NGK plugs (.039, .041, .042, .042)
New OEM Map sensor with “updated” zip tie holder
New OEM PCV valve
Billman’s TCT
Cleaned IACV completely
ECU relearned
The only thing I didn’t do is clean the throttle body and MAP channel out. Last time I had the intake off I noticed very little carbon build-up. IACV wasn’t that bad either as the car only has 53k miles on it. Oil level is full and fresh (lol), and fresh 93. I’m thinking try cleaning the throttle body/map channel anyway? Perhaps a valve adjustment? Quickly running out of ideas, or is this common behavior?
10-15-2018, 02:27 AM
#2
Thread Starter
Hiya,
Some of this is just the way the ECU is. The best suggestion I can give you is
- wind down the gears when stopping, I don't got neutral, wait until rpms are below 2k then clutch in.
- or down shift as you slow, again the final clutch in below 2krpm
Do an idle relearn, then change your driving habbits to be one of the two above, instead of clutching to neutral at higher rpms. Drive like above, after and idle relearn and it shouldn't hesitate when blipping throttle at idle any more.
I struggled with this alot when I picked up the s2k, but a major part of the reality is, AP1s love engine braking so much that the ECU becomes dumb and likes to stutter if you never engine brake. Was even worse with A/C on.
Also make sure when you do an idle relearn it truely has sat overnight and is cold(below 100°F) and can go through a full warm up cycle idling with everything off.. again I'm sure most of this you know/knew. Alot of it is the idle relearn, driving habbits just enhance a bad learn.
Not engine braking, doesn't give the ECU a chance to learn to correct the fuel trims on a controlled deceleration of rpms(ie in gear, motor forced to brake at the rate the rest of the driveshaft spins) once the ECU gets some miles, you can clutch in and it knows how to catch itself at the proper idle. So it works for a while, but if you go back to old habbits(ie always clutching never engine braking), it learns, and will eventually begin to stumble again.
If you keep engine braking as part of your driving..well idle stumble is but a thing that once annoyed you.
Tl
r don't mind my long post lol
Some of this is just the way the ECU is. The best suggestion I can give you is
- wind down the gears when stopping, I don't got neutral, wait until rpms are below 2k then clutch in.
- or down shift as you slow, again the final clutch in below 2krpm
Do an idle relearn, then change your driving habbits to be one of the two above, instead of clutching to neutral at higher rpms. Drive like above, after and idle relearn and it shouldn't hesitate when blipping throttle at idle any more.
I struggled with this alot when I picked up the s2k, but a major part of the reality is, AP1s love engine braking so much that the ECU becomes dumb and likes to stutter if you never engine brake. Was even worse with A/C on.
Also make sure when you do an idle relearn it truely has sat overnight and is cold(below 100°F) and can go through a full warm up cycle idling with everything off.. again I'm sure most of this you know/knew. Alot of it is the idle relearn, driving habbits just enhance a bad learn.
Not engine braking, doesn't give the ECU a chance to learn to correct the fuel trims on a controlled deceleration of rpms(ie in gear, motor forced to brake at the rate the rest of the driveshaft spins) once the ECU gets some miles, you can clutch in and it knows how to catch itself at the proper idle. So it works for a while, but if you go back to old habbits(ie always clutching never engine braking), it learns, and will eventually begin to stumble again.
If you keep engine braking as part of your driving..well idle stumble is but a thing that once annoyed you.
Tl
r don't mind my long post lol
Thanks for the suggestion; I'll give it a try.
10-15-2018, 02:34 AM
#3
Glad to hear others experience now and then too 
10-16-2018, 01:20 PM
#4
I had this exact issue getting worse last year, and I did all of the steps you listed plus I also cleaned out the MAP channel out after taking the throttle body off (and cleaning it too). Like yours, there was a little crud in there at the bottom but it wasn't too bad. Night and day difference. Stuttering stopped. I think these cars are sensitive to certain things and having unrestricted airflow to the sensors is key.
Here's my write up (scroll down a bit):
https://www.s2ki.com/forums/s2000-un...neric-1180453/
If you want to compare crud deposits I can dig up a picture of it if it'll helps.
Here's my write up (scroll down a bit):
https://www.s2ki.com/forums/s2000-un...neric-1180453/
If you want to compare crud deposits I can dig up a picture of it if it'll helps.
10-16-2018, 03:02 PM
#5
The engine behaviour sounds like a classic IACV symptom to me. To clarify, when you worked on the IACV did you remove the electric motor (which is attached with 2x pentacle bits) and spin the valve a lot? It may look perfectly clean however if it isn't free to spin it will always cause problems.
Simply cleaning it isn't fixing the issue.
Simply cleaning it isn't fixing the issue.
10-17-2018, 03:00 AM
#6
The engine behaviour sounds like a classic IACV symptom to me. To clarify, when you worked on the IACV did you remove the electric motor (which is attached with 2x pentacle bits) and spin the valve a lot? It may look perfectly clean however if it isn't free to spin it will always cause problems.
Simply cleaning it isn't fixing the issue.
Simply cleaning it isn't fixing the issue.
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10-19-2018, 12:34 PM
#8
Thread Starter
Just following up. Before taking anything else apart I followed the advice given by Deckoz. Actually I had the battery disconnected again as I’m doing some work on my cluster, so the car was basically stalling out as I pulled it out to go get the last fill up of the season before putting the car away. Rather than wait for the learn procedure I just went for a drive instead; a rather spirited one at that. I did plenty of engine braking and the like.
Problem solved. She runs like a peach now and returns to idle smoothly. I think one of the issues before was I did the idle relearn procedure ONLY, but no driving. I think I may have made this thread a little too prematurely...The car being driven and run through the gears and RPM range also is necessary I feel.
Problem solved. She runs like a peach now and returns to idle smoothly. I think one of the issues before was I did the idle relearn procedure ONLY, but no driving. I think I may have made this thread a little too prematurely...The car being driven and run through the gears and RPM range also is necessary I feel.
10-19-2018, 04:05 PM
#9
Community Organizer
Idle re-learn is different every time, I recently did an airbag swap and noticed that the car idles different than before after reconnecting the battery. I drove the car this time and not just let it idle, it does not dip below 700RPM when I stop at a light now.
10-19-2018, 10:22 PM
#10
Thread Starter
Yeah I think in the future when I get it out of storage again I'm going to start it up, run it for a couple minutes or so just to check for leaks and overall health, and then be on my way. I'm no expert, but this clearly worked out better for me than following procedure. The car just begs to be driven in every situation.