98 Civic EX 5-speed - VERY CONFUSED - Idle Setting
06-22-2012, 07:08 AM
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98 Civic EX 5-speed - VERY CONFUSED - Idle Setting
There seems to be contradicting information from Honda regarding the proper way to set the Idle Screw on 1996-2000 Civics.
I own a 1998 Honda Civic EX with D16Y8. I am in Canada, so idle settings are different. It's a Manual trans as well. My engine should idle at 750 when hot and no loads.
The regular service manual way is to heat the engine up, disconnect the IAC connector, and get the idle as close to 450 RPM as possible with the Idle Set Screw.
BUT, there's a Honda Bulletin that came out on May 19th, 2006 (Bulletin number 03-016) that states, using a scan tool with Honda data, to set the Idle Screw while watching the "IAC Counts" on the scan tool until the reading is "1".
Well, this almost makes NO sense. Because setting the counts to "1", means the IAC Valve is almost completely closed off, which means the Idle Set Screw would be the only thing letting air into the engine and allowing it to idle!? But at the same time, it also completely makes the first step in diagnosing a faulty IAC useless, because the first step is to disconnect the IAC and see if the RPM's change, if there's no change, replace the IAC!? LOL Well setting the screw until the IAC counts is 1 would ultimately make it so that there IS NO change in RPM when disconnecting the IAC!!?? LOL
If you set it the first way, the IAC counts are usually around 15-25 at idle, which basically adds that extra 300 RPM (750 RPM base idle minus 450 RPM with IAC disconnected = 300 RPM).
I have set mine both ways. I find that setting it the regular way, ignoring the bulletin, makes it so that sometimes the engine almost stalls under load with the clutch pedal pushed in. Setting it the bulletin way, this never happens. I have actually had the engine stall when turning and coasting right after stepping on the clutch pedal (releasing the clutch). It seems like the ECM or IAC are slow to re-act which results in RPM dropping below 600 RPMs and further.
Another thing I don't understand: should an egine's RPM ever go below the base IDLE? I know they do obviously when you put a load on the engine or turn AC on etc., but if base idle is 750, why would the make it so that the engine can drop below this amount?
I own a 1998 Honda Civic EX with D16Y8. I am in Canada, so idle settings are different. It's a Manual trans as well. My engine should idle at 750 when hot and no loads.
The regular service manual way is to heat the engine up, disconnect the IAC connector, and get the idle as close to 450 RPM as possible with the Idle Set Screw.
BUT, there's a Honda Bulletin that came out on May 19th, 2006 (Bulletin number 03-016) that states, using a scan tool with Honda data, to set the Idle Screw while watching the "IAC Counts" on the scan tool until the reading is "1".
Well, this almost makes NO sense. Because setting the counts to "1", means the IAC Valve is almost completely closed off, which means the Idle Set Screw would be the only thing letting air into the engine and allowing it to idle!? But at the same time, it also completely makes the first step in diagnosing a faulty IAC useless, because the first step is to disconnect the IAC and see if the RPM's change, if there's no change, replace the IAC!? LOL Well setting the screw until the IAC counts is 1 would ultimately make it so that there IS NO change in RPM when disconnecting the IAC!!?? LOL
If you set it the first way, the IAC counts are usually around 15-25 at idle, which basically adds that extra 300 RPM (750 RPM base idle minus 450 RPM with IAC disconnected = 300 RPM).
I have set mine both ways. I find that setting it the regular way, ignoring the bulletin, makes it so that sometimes the engine almost stalls under load with the clutch pedal pushed in. Setting it the bulletin way, this never happens. I have actually had the engine stall when turning and coasting right after stepping on the clutch pedal (releasing the clutch). It seems like the ECM or IAC are slow to re-act which results in RPM dropping below 600 RPMs and further.
Another thing I don't understand: should an egine's RPM ever go below the base IDLE? I know they do obviously when you put a load on the engine or turn AC on etc., but if base idle is 750, why would the make it so that the engine can drop below this amount?
06-22-2012, 01:33 PM
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Re: VERY CONFUSED - Idle Setting
O would have to double check but I believe you are also suppose to put a pin in the service connector similar to when you are going to check the engine codes or adjust the timing.
I would ignore the honda bulletin for the purpose that most people are not going to have the scan tool needed to do it that way. Especially considering that is sounds more complicated and less accurate.
The engine load detector/ PSP sensor/ and circuit that increase idle with higher engine load are not the fastest it does take them a second to realize that they are needed when you first turn one of these systems on or turn the steering wheel at idle. The IACV being dirty could cause the problem of stalling out on you when you push the clutch in and idle dropping too low.
I would ignore the honda bulletin for the purpose that most people are not going to have the scan tool needed to do it that way. Especially considering that is sounds more complicated and less accurate.
The engine load detector/ PSP sensor/ and circuit that increase idle with higher engine load are not the fastest it does take them a second to realize that they are needed when you first turn one of these systems on or turn the steering wheel at idle. The IACV being dirty could cause the problem of stalling out on you when you push the clutch in and idle dropping too low.
06-23-2012, 04:27 AM
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Re: VERY CONFUSED - Idle Setting
That image says "Adjust the idle speed using a Honda PGM Tester if possible..." at the very beginning...
I have MotorAllData as well and for my car specifically it shows a different method where you disconnect the IAC and then set it to 450 RPM rather than 750 RPM with it plugged in...I guess it's really the same either way...
I have MotorAllData as well and for my car specifically it shows a different method where you disconnect the IAC and then set it to 450 RPM rather than 750 RPM with it plugged in...I guess it's really the same either way...
06-23-2012, 05:27 AM
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Re: VERY CONFUSED - Idle Setting
First, what exactly are the idle problems you are having? Are any CEL codes thrown? Have you cleaned your IACV?
Not true. The throttle plate never completely closes, so the engine also gets air that passes through this opening.
Would you please post Bulletin 03-016 so that we can read the procedure.
Sorry, I don't understand your points. You would try to adjust the idle speed only after you had done the diagnostic procedures.
And when the IACV is working, it is bypassing air to the IM, thereby elevating the idle speed. Unplugging the IACV would largely prevent the air bypass, causing the idle speed to drop, as expected.
Are you saying that you solved the problem adjusting the idle speed using the bulletin method?
No, your engine idle speed should never drop below 750 rpm, even when the A/C is turned on. In fact, under conditions of extra load, the idle speed should rise (see diagram).
BUT, there's a Honda Bulletin that came out on May 19th, 2006 (Bulletin number 03-016) that states, using a scan tool with Honda data, to set the Idle Screw while watching the "IAC Counts" on the scan tool until the reading is "1".
Well, this almost makes NO sense. Because setting the counts to "1", means the IAC Valve is almost completely closed off, which means the Idle Set Screw would be the only thing letting air into the engine and allowing it to idle!?
Well, this almost makes NO sense. Because setting the counts to "1", means the IAC Valve is almost completely closed off, which means the Idle Set Screw would be the only thing letting air into the engine and allowing it to idle!?
Would you please post Bulletin 03-016 so that we can read the procedure.
But at the same time, it also completely makes the first step in diagnosing a faulty IAC useless, because the first step is to disconnect the IAC and see if the RPM's change, if there's no change, replace the IAC!?
LOL Well setting the screw until the IAC counts is 1 would ultimately make it so that there IS NO change in RPM when disconnecting the IAC!!?? LOL
If you set it the first way, the IAC counts are usually around 15-25 at idle, which basically adds that extra 300 RPM (750 RPM base idle minus 450 RPM with IAC disconnected = 300 RPM).
And when the IACV is working, it is bypassing air to the IM, thereby elevating the idle speed. Unplugging the IACV would largely prevent the air bypass, causing the idle speed to drop, as expected.
I have set mine both ways. I find that setting it the regular way, ignoring the bulletin, makes it so that sometimes the engine almost stalls under load with the clutch pedal pushed in. Setting it the bulletin way, this never happens. I have actually had the engine stall when turning and coasting right after stepping on the clutch pedal (releasing the clutch). It seems like the ECM or IAC are slow to re-act which results in RPM dropping below 600 RPMs and further.
Another thing I don't understand: should an egine's RPM ever go below the base IDLE? I know they do obviously when you put a load on the engine or turn AC on etc., but if base idle is 750, why would the make it so that the engine can drop below this amount?
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