Engine idle bog, dip, studder, stalling, etc
 

This question gets posted a TON. The symptoms are any of the following:

Engine idle dips really low when coming to a stop, and car sort of "shudders" because rpms get down to 300-400 rpm.

When at a stop, after giving a small amount of gas, and then pushing the clutch back in, such as backing out of a parking space, etc, the engine idle dips low and almost stalls.

Any other variation of the above. I will add other specifics as they become available.


So now that this happens, here are the steps and solutions to this problem.


First, understand that our ECU is a "learning" ECU. It is taking readins from many different sensors and adjust timing and fuel mappings based on the readings it gets from these sensors. At times, the readings can conflict for one reason or another, and cause the ECU to become confused. This is THE MOST COMMON reason for this bogging idle.

When this happens, DO NOT give the car gas, as it makes it more difficult for the ECU to "relearn". This ECU confusion occurs most often when there is a big change in temp or humidity in the atmosphere.

So:

1. Give it a couple days. The idle problem will most likely go away on its own. Though keep in mind it can come back again when the same conditions occur again! This is normal for our cars!

2. If after several days, this problem is still constant, try the "map sensor whack" located here:
https://www.s2ki.com/forums/index.php?showtopic=209708
Also, securing the map with the "zip tie" method may help.

3. If this does not work, clean the IAC motor. I will provide more specifics and possibly pictures on how to do this if I can. When you clean the IAC motor, if you notice a lot of oil and very thick crud in the area, you may need to install a catch can or figure out why you're getting so much oil blow by into your TB area from the PCV.

4. If that still does not work, you may need to replace the map sensor. (this does happen!)

5. If that doesn't work, then you may need to replace the IAC motor, though generally, this causes a high and low erratic idle when it goes bad.

This is great info! Thanks!!

Good info...much appreciated. :thumbup:

BUMP

should be must read for n00bs

I have found that this complaint often comes in the spring, about when the switch from winter gas to summer gas occurs. The suggestion to wait before taking action can work as the weather and gasoline will change eliminating the condition.

On my car I have found tht cleaning the TB occasionally helps. I don't think I have a serious blow-by problem, but the cleaning after a few years still helps.

Interesting. I noticed this in my car about a month ago. It slowly went away. I thought it was almost going to stall a couple of times.

It went away and the car has been running great. 46k miles.

thanks for the info.

Great information, thanks for putting it together

I thought I read that you have to retrain the ECU when disconnecting the battery or the backup fuse by starting the car and holding the RPMs at 3K for 5 minutes. Is this true?

no when you reset the ECU disconnect the negative on battery, reconnect after 15 min or so then just turn the car on, and let the fan cycle three times.. some people like to drive it immediately after to begin the learning process but you dont have to

Thanks a lot, always contributing to the s2ki community...Seriously this was a quesiton I wanted to ask and searched, but couldn't find results like this...THANKS AGAIN...

So, a quick question,

My 04 when it is cold in the morning will stutter really bad when it starts, I give it a little gas and it goes away and is never an issue until the next morning when it is cold.

Do your solutions pertain to this issue as well, so should I just let it stutter and let the computer "learn".

Thank you for putting this together. I have gathered so much useful information from this site and appreciate the time you and others put into it.

Take care

I knew I read it somewhere. It's called the Idle Learn Procedure, from page 11-100 of the S2000 00-03 Honda Service Manual (sorry for the cut and paste from the PDF)

The idle learn procedure must be done so that the ECM
can learn the engine idle characteristics.
Do the idle learn procedure whenever you do any of
these actions:
. Disconnectth e batterY.
. Replaceth e ECMo r disconnecti ts connector'
. Reset the ECM.
NOTE. Eras\ng DTCS N\th Honda PGM Testei does
requiret he idle learnp roceduret o be done again.
. Removeth e No.6 ECU( ECM)( 15A)fusefr omt he
under-dashfu se/relayb ox.
. Removet he No. 41 BATTERY(1 00A)f usef rom the
under-hoodf use/relayb ox.
. Remove the PGM-FI main relay.
. Removet he batteryw ire from the under-hoodf use/
relay box.
. Disconnecat ny of the connectorsf rom the underhood
fuse/relay box.
. Disconnectth e connector( C404)b etweent he
dashboard wire harness A and dashboard wire
harness B,
. Disconnectth e Gl terminal.
. Adjust the idle speed.
To complete the idle learn procedure do this:
1. Makes ure all electricali tems (A/C,a udio,r ear
window defogger,l ights,e tc.)a ret urned off
2. Startthe engine. Hold the engine speed at 3,000
rpmw ith no load( inP arko r neutralu) ntilthe
radiator fan comes on, or the engine coolant
temperaturere aches1 76'F( 80") 212"F{ 100").
3. Let the engine idle for about 5 minutes with the
throftief ully closeda nd with all electricailt ems off.
NOTE: lf the radiator fan comes on during this step, the
time when it is operating must not be included in the 5
minutes.

haha ... you can have fun with that one

the learn procedure is not necessary, but there is also nothing wrong with doing it either.

nad just so you see how its done on here i thought i would should you the DIY link that xviper posted up

https://www.s2ki.com/forums/index.ph...ic=183490&st=0

What would be the best way to cure it?

Thanks,

are you wanting to cure the engine idle, or the learning prcoess... either way its cured by just driving it.

It is only on start up that I have the problem and on very cold mornings. I live in Colorado so it is dry as hell as well, so humidity isn't an issue.
I have never had a problem with idling while driving, only on the start up.

Thoughts?

Maybe this is a dumb question but would it help/hurt to spray some contact cleaner before connecting the plug back together?

I've experienced another cause of rough idle and bogged throttle that is not listed here, or for that fact on any other thread that i could find here.

Actually I just discoved what was causing the issues today. About a month ago i blew a piston ring and had to take my S to the shop. The repair required extracting the engine and taking it apart. A couple weeks later I get her back and the problems start. The second day of driving the rebuilt S the idle was noticably shakey "shuddering". Not just upon start up, but at stop lights even after hours of driving. Another thing i noticed was hicuppy/bogged acceleration through 1st and some of 2nd gear.

I called the shop after about a week and he said it could be the injectors or a bad sensor. NO. after carefully examining the engine compartment and taking notice of a new constant hissing noise at idle, it turns out they never reconnected the air control solenoid sensor. On top of that they miss connected the vacuum hoses to the sensor as well! Here are some pictures to illustrate

Attachment 127395

Attachment 127396

Attachment 127397

By following xviper's CAI Vacuum Line Routing DIY i got corrected.

Due to the fact that the all the hoses and connections had to be taken off and put back together as process of the piston ring repair i was starting from scratch hunting down the culprit.

I couldn't find threads regarding this same issue causing Idle/throttle problems, hope someone finds this helpful.

Lot of good info in here i followed something similar to the OP's info to fix my crx after her swap. Turned out the IVAC had to much carbon build up by like he stated it will be more like the car is reving itself. Well atleast in my case.

Thanks guys I've been having this problem for a while. I ll give it a try.

thanks for this!!

Do you guys think this type of problem would be common on an Integra Type-R as well?

i have the exact same issue as the original post from wisconsin582:
Engine idle dips really low when coming to a stop, and car sort of "shudders" because rpms get down to 300-400 rpm.

When at a stop, after giving a small amount of gas, and then pushing the clutch back in, such as backing out of a parking space, etc, the engine idle dips low and almost stalls. Also, the car has backfired twice when coming off the line while running in this state. The problem is intermittent.

Wisconsin582, have u found the exact cause? Has anyone else had this same exact problem and what was the fix? thanks

Great thread. I've had this happen a few times. I am glad I'm not the only one.

here's our stalling studdering thread you might want to check out

https://www.s2ki.com/forums/index.ph...&f=22&t=478799

THis was happenening when i was driving my 240 and my dad said dont worry about its the computer thinking, he never explains anything. Problem went away and now i understand. Great post.

- i happen to have an idle that more often than not, does not drop down, settle in, to the normal idle speed...it tends to hang up a few hundred rpm, then drops to normal.......sometimes the throttle lacks that "surgical" response when trying to blip it from idle -- any ideas..

-- i have checked for leakage, since i have a K&N air intake...the filter with tube and box in place of where stock box was

-- it was perfect until installing the K&N, so something from the install is the culprit, just sorry to feel that this will be the price of having the K&N

I would say check the vacuum lines, though you'd likely experience a CEL if they are incorrectly connected.

Helpful thanks :D

I don't think it was helpful, since it doesn't give a cause or a cure! There are several threads alluding to this same problem, but none of them pinpoint a cause or a cure (unless you count Shock wrecking his car and actually being relieved(!) because he didn't have to deal with the idle/stalling problem anymore). They just document the owner's endless efforts at troubleshooting.

This problem seems to be widespread on S2K's; does anyone know the cause and/or how to fix it?

also coasting to red light and stuff in neutral will make the problem more apparent. Its confuses the ECU because the it senses the speed of the vehicle but the engine is trying to maintain an idle..search it up !!

So its normal when ever I disconnect the battery and then reconnect for my car to do this? I've had to disconnect it two times this week (installing new EPS / installing test pipe) and both times the car has a really low idle and stales? The car is acting fine now, I guess its just really weird for me since I've never had a car do this before. I thought it was a bad ground! Thanks for the information!

yup same here i had that issue this morning i diconnected my ecu to reset it and was doing the exact same...i hope it goes away fast

What if I am running an AEM Series 2 Plug & Play EMS? I don't believe it is a "learning EMS" as it does not use the O2 sensor for any feedback to manage the engine fuel & timing. It is my understanding that everything is set up by the tuner. If that's the case, why would I have an intermitent erratic (low) idle. When the cooling fans kick on the idle will drop down really low as well.

I also notice that the throttle will "hang" between shifts if I shift around 3,000rpm. This problem is not apparent at higher or lower rpms.

I am running a Vortech SC with a 4 bar MAP (new in Nov 2010) and the PCV is going to a catch can.

Any ideas? Maybe the IAC? Any help would be appreciated!

Chris

I agree with the OP. Good info there. As for the relearn idle procedure, if you every disconnect the battery and reconnect, it may be helpful to do the relearn. I had a low idle and hesitation to point of almost stalling, after disconnecting the battery for some work. I re-disconnected the battery to reset ecu, then did relearn idle procedure (good to have 2nd person watch when radiator fan comes on), and idle is all good now. It idles higher and no hesitation. If this doesn't help then revert to OP's post

What is a IAC?

Sorry for the bump, but the link for the "whack" method is dead(or is it just me?) can anyone explain how to do this method?

EDIT: I'll just leave this here for future reference:
http://forums.s2kca.com/showthread.p...MAP-Whack-quot

Could this problem also include shuddering/stalling when starting to accelerate from a stop? I get a slight shudder sometimes when stopping quickly, but its more noticeable at times when starting.

Great info this is what mine is doing, I have just got it, its been parked for months and had a flat battery

Great thread

I had this issue and getting a new battery resolved it.

I just had the same experience for about 3 weeks of ownership. It never do that in this past 3 weeks. Tonight, i went out to get gas. Everything is find until i was on my way home, and coming to a roundabout, i brake and slow down the car, downshift to 2nd, and then the car stalled. NO CEL. I was stopped in the middle of the road. I tried to restart the car, it was difficult to start. It cranked, but did not start.
I tried to restart twice, and it didn't work. After 30 seconds, i tried again, and it started right up. i couldn't seem to find anything wrong with the car, i didn't feel the engine is bogging or bad idles, etc.

This happened again when i am approaching my driveway, downshift to 2nd, and speed is quite slow as i am getting ready to get on my driveway ramp. It stalled. And again, i had difficulty to start the car immediately. I have to give it a decent 30 sec to a min, it started right back up.... Still no CEL....

what's the problem here? i don't wanna get strand in the middle of the road again. It was quite dangerous.

I got into this situation here also where it stalled out and took a bit longer to crank over in traffic on a highway.

I have replaced the MAP sensor and the IAC motor with OEM units and its still acting the same. I've cleaned out the TB but I have a feeling it may be a sticky butterfly that could be causing this.

I would check the engine ground cable on the back of the head, this seems to cause different issues and replacing it has helped many owners.

There is a recent thread describing this. Good luck.

https://www.s2ki.com/forums/s2000-un...ts-up-1108318/

thanks Hfreak, i just took the car out and i noticed the car had stalled even when it was dropping back to idle at 5-600 rpms.