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Discussion Starter · #1 ·
Hi, my car has been stalling during my daily driving and I found a vacuum leak. There was a hose that leads to the back of the intake manifold that connects to the vacuum tank and then to the cruise control. when connecting the hose, the engine dies at idle but when off it starts and idles fine. Does anyone have any ideas for this?
 

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You need to give the ECU time to relearn idle air control motor position now that the vacuum leak has been fixed.

It learned to control idle RPM with the vacuum leak, and it realized it didn't need to open the IAC so far to maintain idle. Now that you fixed the vac leak, the ECU got used to relying on that air as a source during idle. Now you've shut that air source off, and ECU needs to relearn how to maintain idle with only IAC supplied air.

Disconnect the battery for a minute, then reconnect, and make sure your vacuum hose is fixed and hooked to the intake, then start the car. Disconnecting the battery should reset IAC adaptives, and force the ECU to command more IAC duty during next start up and idle scenario, and it will trim IAC duty as necessary to control idle RPM. It shouldn't take long after that before the car starts idling normally again.
 

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Discussion Starter · #3 ·
You need to give the ECU time to relearn idle air control motor position now that the vacuum leak has been fixed.

It learned to control idle RPM with the vacuum leak, and it realized it didn't need to open the IAC so far to maintain idle. Now that you fixed the vac leak, the ECU got used to relying on that air as a source during idle. Now you've shut that air source off, and ECU needs to relearn how to maintain idle with only IAC supplied air.

Disconnect the battery for a minute, then reconnect, and make sure your vacuum hose is fixed and hooked to the intake, then start the car. Disconnecting the battery should reset IAC adaptives, and force the ECU to command more IAC duty during next start up and idle scenario, and it will trim IAC duty as necessary to control idle RPM. It shouldn't take long after that before the car starts idling normally again.
That is very good info to know ill go try it and let you know what happens thanks, man.
 

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Discussion Starter · #4 ·
You need to give the ECU time to relearn idle air control motor position now that the vacuum leak has been fixed.

It learned to control idle RPM with the vacuum leak, and it realized it didn't need to open the IAC so far to maintain idle. Now that you fixed the vac leak, the ECU got used to relying on that air as a source during idle. Now you've shut that air source off, and ECU needs to relearn how to maintain idle with only IAC supplied air.

Disconnect the battery for a minute, then reconnect, and make sure your vacuum hose is fixed and hooked to the intake, then start the car. Disconnecting the battery should reset IAC adaptives, and force the ECU to command more IAC duty during next start up and idle scenario, and it will trim IAC duty as necessary to control idle RPM. It shouldn't take long after that before the car starts idling normally again.
After following what you said, I disconnected the battery for 2 minutes roughly and the car started fine but after driving the car died on me 3 times and idles at about 100rpms and we are here now
 

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Discussion Starter · #5 ·
Yesterday I started a discussion post based on a vacuum leak. After following the instructions provided my car now has a hard time starting, it takes a minute to start getting some combustion unlike when I had the vacuum leak. also after the car warms up from idle, the RPMs drop to about 200 and when I give it gas the car dies after the RPMs come down. Could there be another leak somewhere or is it something else?
 

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So the car is still starving for air. Need to continue diagnostics. Didn't need to create another post either lol.

How long do you think the vac leak occurred? Was there any other symptoms of a vac leak before other than you just happened to notice it one day? Does it start ok when you crack the throttle a bit manually with your foot?

What kind of mods does the car have? Engine type? Intake/TB?

Pictures?
 

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Discussion Starter · #7 ·
So the car is still starving for air. Need to continue diagnostics. Didn't need to create another post either lol.

How long do you think the vac leak occurred? Was there any other symptoms of a vac leak before other than you just happened to notice it one day? Does it start ok when you crack the throttle a bit manually with your foot?

What kind of mods does the car have? Engine type? Intake/TB?

Pictures?
The vac leak was probably there for months. I just recently started having issues where the car would not accelerate after giving gas and the car would come back to life after catching whatever it is. Doesn't happen when I accelerate, only when I let off the gas does the issue occur. my thought is its fuel-related, I had a bad fuel leak when one of my injector seals was torn and I went through it all. The engine is D16Y8 in 97ex Sedan with an eBay cold air intake, Y8 intake manifold, and stock TB. Long ago I had an idle problem where my IACV would act up and cause my car to shutter while driving that hasn't happened in a long time and I also replaced the part but it never fixed the issue so I am wondering if it finally caught up. I also replaced a heater core so not sure if that's relevant.
 

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Try adjusting the IAC bleed air screw, this one:

136716



Your TB may or may not have a cap over this screw, hiding it. Turning the screw in closes the bleed air passage, loosening it opens it. Try turning it out a bit and see if it starts to idle properly. Go slowly, no more than 1/4 turn at a time. Then retry another start without touching the throttle. Keep trying and repeating to see if you can regain control of the idle without having to press the throttle. If you end up pulling the screw all the way out, and it still dies when trying to start at idle, you either have severe IAC or passage blockage issues, or another underlying issue that is not related to airflow through TB or IAC.
 

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Discussion Starter · #9 ·
Try adjusting the IAC bleed air screw, this one:

View attachment 136716


Your TB may or may not have a cap over this screw, hiding it. Turning the screw in closes the bleed air passage, loosening it opens it. Try turning it out a bit and see if it starts to idle properly. Go slowly, no more than 1/4 turn at a time. Then retry another start without touching the throttle. Keep trying and repeating to see if you can regain control of the idle without having to press the throttle. If you end up pulling the screw all the way out, and it still dies when trying to start at idle, you either have severe IAC or passage blockage issues, or another underlying issue that is not related to airflow through TB or IAC.
[/QUOT
Try adjusting the IAC bleed air screw, this one:

View attachment 136716


Your TB may or may not have a cap over this screw, hiding it. Turning the screw in closes the bleed air passage, loosening it opens it. Try turning it out a bit and see if it starts to idle properly. Go slowly, no more than 1/4 turn at a time. Then retry another start without touching the throttle. Keep trying and repeating to see if you can regain control of the idle without having to press the throttle. If you end up pulling the screw all the way out, and it still dies when trying to start at idle, you either have severe IAC or passage blockage issues, or another underlying issue that is not related to airflow through TB or IAC.
Sorry for the late response, I had a mechanic look at it but they couldn't fix the idle and stalling issue. when the car idles it's at about 200rpms and is fine when its first started. they said the car needed gas and it was fine. When getting into gear the car doesn't cut out anymore but the car dies if it isn't constantly getting gas. Throwing it into neutral kills the car and I have to start it again. this goes for being in gear but obviously the process is slower. No vacuum leaks, the only thing that's could be causing the issue is the Walbro 255 I have in the tank its the only option at this point but I don't know why. they tested it and the line and said it failed but still working properly and the mechanic put it back in after inspection. so I'm running options and my parents are losing patients.
 

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any progress on diagnosing?

What are the CURRENT symptoms.

Describe in detail, nothing is too dumb sounding.
 

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high flow/pressure fuel pump doesnt seem to mingle with the idea of fast starting, but stalling at idle.


OP, Id try unplugging the IACV, and using the idle adjust screw to bring it to a normal idle. Probably best to run the dile screw all the way down (DONT DO IT HARD) then back it out 3 full turns.

In a perfectly normal car, unplugging the IACV should make the car idle around 400-500 rpms, so that is why you must loosen it further to get a higher idle.


If all your problems go away, your IACV is simply dirty and sticking, or its junk and needs repalcement.


Simple check
 
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