Vtec_India

hi Ohmega,
The information provided is nothing less than a holy grail of honda much talked IACV valve which I understand is mostly the cause behind idling issues.

Issue
I am facing a strange issue..(more so during winters temp 30-50* F) the car starts to die when I depress the clutch at a stop light. The occurrence seems to be more or less random. So far only pattern I could understand is that it happens more during cold weather and it happens more when I bring the running car to a halt by letting go the accelerator pedal. If I am at a stop light and the car manages to idle fine then mostly it will idle just fine till it occurs next time at another stop light. Sometimes, pumping the gas pedal brings up the dieing idle.

And also the issue is somewhat less for a few days after I have just cleaned the IACV valve with a throttle cleaner.And then there are days when I don't face any idling issues at all.. It purrs perfect, feels smooth and pounces well..

What I have done so far:-
I periodically clean the IACv as well as the air bypass hole to ensure that the dirt has been thoroughly cleaned from those air bypass holes.A few months back I unplugged the IACV wire harness from the IACV and unscrewed the magnetic Solenoid (green cover) and if i remember correctly, instead of dropping to a base idle, the rpm started oscillating.

I have got the error codes checked by Honda and no error codes have been detected by the scanner.
Car shows the normal behavior of idling high (around 1100-1200 rpm ) during cold start that drops down to 750 rpm once the car is warmed up.
Switching on AC does bump the RPM up by 80-100 rpm -which i think is the correct behavior.
I have tried increasing the warm idle (to 1000 rpm) by turning the idle air bypass screw once and the idling issue vanished for sometime, the idle shuddering vanished as well. However my happiness was short lived as within few weeks the RPM was back to the normal idling rpm of 750 rpm.
I clean my filter regularly and get them replaced as soon as possible to let the car breath freely.
On a hunch that IACV might be working well but may be somewhat sticky or sluggish , I tried souring a new IACV but its cost as well availability within India is an issue as this model has now became a sort of legacy and parts are not available.


Mine is a VTEC ( B15C - Indian version which is more or less similar to del sol/US civic between 1996-1998) and has a three pin IACV.


Has anyone faced this car stalling issue as weird as this?

Please advice.

I wonder...
If I block the IACV air bypass hole with a tape, what ideal behavior shall I expect?
If I disconnect the IACV harness what should be the expected behavior?
Can I block the IACV permanently by putting a tape over the hole and bumping up the idle RPM using the idle bypass screw to say 900-1000. Will this manage the use of AC in summer as well? Or any other load event for that matter.
Any other workaround that can solve this issue?


Thanks much in advance guy!

Vtec_India

Hi Ardee,
My issue is almost similar - the idle is bad at times, the car dies sometimes while coming to a stop. There is no error code. Pumping brake paddle makes the Idle rpm rise a bit at times.

And then there are times when the car performs flawlessly.. as if it has a mind of its own.. for now I have been revving the car when i come to a stop and use hand brake to stop. Mechanics have given a clean chit to IACv, vaccum leak or any other issue that impacts idling... some are advising me to carry on which this little trouble...So far.. I am more or less clueless..

Ohmega

iTrader: (1)

Make a new thread with everything you just typed here (add vehicle information and engine info too!), and more people can help you with your problem.

Two things stood out in that paragraph to me. You said you adjusted the base idle screw. In order for the idle to be properly set, the IACV has to be unplugged.

And for the love of god, don't stick any tape in, on, or around your intake. We recently had a user on this forum document the destruction of his car. The fiasco more or less ended with him sticking paper towels in his IACV port- killing his car.

Miguel Munoz

This could be a cause of dirty fuel injectors. Buy some fuel injector cleaner and run the car on a full gas tank. If you could also try finding a MAP sensor and replacing your old one. Always start out with the less costly options. I guarantee fuel injector cleaner should solve this issue.

Ardee99

Thanks India good to know I am not the only one.

What have you done or replaced on the Honda? So far I have only replaced the IACV. I am going to perform a smoke test this weekend to see if I can locate a leak.

Again ANYONE who has some thought on our issues please help

Vtec_India

Thanks a lot for your replies.

Ohmega,
I did disconnect the IACV harness before attempting the idle adjustment using the idle adjustment screw. Sorry I forgot to mention that in the post above.

I wouldn't wanna hurt my car.. so in the first phase of troubleshooting, just trying all the adjustments that are reversible without much impact on the car/engine.
Secondly, I am trying to simplify the equation by striking off the variables one by one and hence my thoughts around moving the IACV out of the equation temporarily and figuring out a good way to do that.

Miguel,
My car has run 92K KMs and in the last major service i.e. at 80K the injectors were cleaned and the fuel filter was replaced as well.

One quick question.. If i bump up the RPM to say 900-1000 range.. then after a while, does it come back to the factory set RPM (750 - The current RPM I have)? Have you seen this happening?

Vtec_India

Well, I have tried everything i guess except replacing throttle body that is not available or even if I get it it will cost more than the cost of the car. Following are some of the things I got done from honda/myself
1. coolant/antifreeze replaced and air bled from cooling system
2. Tappet adjustment
3. ECU scan for retrieving any error codes - No error codes detected
4. Bumped up Idle rpm using idle adjustment screw twice - Only to find that it reverts back to factory idle rpm (750) in a few weeks
5. Change air filter frequently
6. Keep cleaning throttle body using a throttle body cleaner almost every two weeks - Getting sick of it
7. Did a vaccum leak diagnosis using throttle body cleaner - No vaccum leak
8. Use hand brake to come to a stop and keep revving engine to not let it die.. (Mine is a stick shift) - unfortunately forcing the drivers of the nearby cars to start prepping up for an unintentional drag race


and above all tried convincing my co-passengers that mine is a track racer who doesn't like to stop frequently and talk to my car to convince her to behave properly..

Ohmega

iTrader: (1)

I have a feeling this may or may not be related to air.

Take off your intake tubing and locate the IACV hole in the throttle body. There should be suction when you cover it with your finger, and the engine will want to die.

If there is no suction present I would venture to say your IACV has failed, but do that preliminary test, then we can test the IACV more thoroughly. We just have to narrow down the issue.

Vtec_India

Hi Ohmega,

Sure.. Will do that test tomorrow.

I am curious.. wouldn't engine should settle to its base RPM if I block the IACV hole as it will still suck in air from the air bypass valve located at the back of the throttle body?. Something similar to the procedure for setting up base idle rpm with IACV harness disconnected?

Ohmega

iTrader: (1)

I'm not familiar with your engine. Provide your vehicle information please.
year, model, engine code, ecu

Vtec_India

Following are the specifications for the type of engine I have in the Bay.. This model was specific to Asia/India and was code named SX8 but I think the engine is more or less similar to the one shared by Delsol/Civic in the later half of 1990s-2000 timeframe

Here .. trying to list as much information I have about this engine

Engine type : B15C2 Honda 1.5L 16V SOHC VTEC PGM-FI
Displacement : 1493cc,
Year (In Asia) - 1999-2003
Model Name in India - Honda City Type I/II
Model Name in Asia/Thailand - "City type Z"
Wiki Page - https://en.wikipedia.org/wiki/Honda_City (Go to "Third generation (1996–2002)"
Output - 106 BHP
IACV Type - 3 Pin
ECU type - OBD2b PJT (It has a three pin OBD connector and a 2 pin service connector )
It has a Distributor and has a single ignition coil
The Throttle Body has heated IACV, No FITV, and an idle control bypass valve at the back besides the TPS and MAP sensor
IACV has two holes - front rectabgular hole for IACV and the rear round hole for idle bypass for base idle
It has a PCV hooked somewhere below the intake manifold at the back of the engine block
It doesn't have any EGR Valve




Some threads on Honda-tech on this engine type :

https://honda-tech.com/tech-misc-15/...2812263/page2/

https://honda-tech.com/all-motor-nat...-mods-2976472/

Some other external links
Getting to Grips with a B15C2. - D-series.org
http://www.d-series.org/forums/attac...inoy-vtec1.jpg
http://www.d-series.org/forums/attac...y-engblock.jpg
http://www.d-series.org/forums/attac...chinoy-vin.jpg

This is how the engine bay looks for this model
http://www.team-bhp.com/forum/attach...-more-vtec.jpg


If I have not already confused everyone with the above details , While going through some service manuals for Honda civic 1996-1998 I found most of the parts in this engine resemble D16Y7 engine.. However the capacity has been reduced to 1493 cc to address some engine size government constraints that are local to Indian subcontinent

but again.. I am a noob and I can be totally wrong..

tony_2018

You need to put the ecu into service mode before attempting the adjust idle. i didn't see it anywhere so I'm suggesting it now.

that_boy_sammy

Take your throttle body off and clean it with brake cleaner or whatever solvent bhai. Spray brake cleaner on a shop towel and clean inside your intake manifold bhai. Adjust your throttle cable to where there is 1/2 inch of slack, if too loose the throttle plate will slap to a rapid close when releasing your gas pedal. The iacv does not need to be cleaned frequently. This will work bhaia.

Vtec_India

Great idea!!!! Thats what I didn't do both the times when I bumped up the RPM. Will definitely try that.
Thanks a lot!

Vtec_India

yeah I have done that Multiple times.. earlier I used to go to the local garages to get the throttle body out of the bay and clean it out thoroughly using some good cleaner. But then i hate to see some non technical folks trying to ruin the part as delicate as throttle body so I have been cleaning it myself without taking it off. I follow a three step process
1. Clean the butterfly - Using Throttle cleaner + Soft towel
2. Clean the iacv air flow passage - Just the spray in the cavity
3. Clean the base air flow passage - Same as Above

Sometimes the idling issue goes away temporarily after such a clean only to return back after a week or two.

One observation ( I suppose its not a placebo), is that everytime, I clean the throttle body like that I immediately notice a deeper growl and a crispier, more rev happy and a more eager engine.. I understand after a clean, it breaths easy however what surprises me is that does it get dirty so often?? why?


One more thing.. not sure if its related to my idling issue.. whenever I am in lower gears like 1 or 2 and rpm < 1500. In a bumper to bumper traffic if I let go the accelerator or press it softly the car jerks like too and fro.. before finally smoothing out.. not sure if there is a common reason behind this issue and the idling issue.. but thought i would bring it up..

Vtec_India

Hi guys,
Thanks a lot!
Apologies for delayed response. I had to travel out of country for 2-3 days and later was not well.
I bumped up the idle RPM by putting ECU in service mode (and disconnected IACV connector)and raising the RPMs by around 100 RPM. Now My car is idling at 850 rpm (with IACV connected and ECU in normal mode) instead of earlier 750. Drove for a few blocks and didn't encounter the idling issue.
Monday, when I rejoin my office, will be a good day to test it to see if the problem is rectified for now and if ECU can hold the newer values of idling RPM.
Thanks much!

Vtec_India

A week gone by.. and the engine has stalled just 3-4 times.. I think its a great improvement over the earlier situation..


However, I see that the idle has slowly started inching towards the base RPM of 750 instead of holding steady at the bumped up RPM (800)...