2001 Mercury 115 FOURSTROKE EFI Idle Adjustment

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Author Topic:   2001 Mercury 115 FOURSTROKE EFI Idle Adjustment

rired posted 06-02-2008 11:26 AM ET (US)
Is there a way to adjust the idle speed on [a 2001 Mercury 115-HP EFI FOURSTROKE] motor? [I] was told that [engine speed] should be about 750-RPM in gear. With the throttle fully retarded [my engine idles] at 500-RPM.
Tohsgib posted 06-02-2008 11:28 AM ET (US)
The only way is to adjust the throttle is the cable itself at the engine. If there is no adjustment there then it might have to be done with a computer at the shop.
Tohsgib posted 06-02-2008 12:16 PM ET (US)
Adjust the cable at the engine a turn or [two].
Tohsgib posted 06-02-2008 12:18 PM ET (US)
My Suzuki really has no adjustment. You adjust the cable so it runs all the way to WOT and then the computer sets the idle. Not sure if yours is the same but can't hurt trying the cable, just make sure you are getting WOT when adjusted.
jimh posted 06-02-2008 10:58 PM ET (US)
These motors are actually Yamaha power heads bought by Mercury. (They bought 70,000 of them.) The fuel injection is probably from Yamaha, and I don't think it is particularly sophisticated, that is, you don't make adjustments to it with a computer--it does not have stored code or erasable memory.
itl posted 06-03-2008 05:54 AM ET (US)
You can't adjust idle speed of that engine or basically in any EFI engine without doing some magic to engine software.
Idle speed is computer controlled. If it is not in correct range, then there is some problem in your engine.
Typically the computer (ECU, EMM or whatever you call the engine control unit) adjust the idle stabilation valve based on information what it gets from various sensors (engine rpm, engine temp, maf/map etc). Idle stabilation valve then set how much engine gets air in idle speed, amount of air actually sets the idle speed in the range where it should be. That is the basic principle how idle is set in (any) EFI engine. Computer is continuosly checkin idle speed and if idle goes lower than it should then ECU opens the idle stabilation valve and if idle is too high then ECU closes the valve. Pretty simple actually.
Typical problems with the idle speed are air leaks in manifold or somewhere else in air intake after amount of incoming air is measured or incorrect fuel adjustment.
jimh posted 06-03-2008 08:19 AM ET (US)
Are you saying that to make adjustments to all electronic fuel injected engines you have to connect a terminal to a serial data port and make changes to the stored algorithm which controls the functioning of the engine? This is at variance with my experience, as I have never heard anyone mention that a serial data connection exists on these Yamaha EFI motors to which one could connect a terminal.
My impression of these Yamaha motor fuel systems is that the programming which controls them is fixed and the circuitry contains analogue techniques as opposed to being strictly in the digital realm and using stored code which can be field modified or re-programmed.
I love to peak under the hood of modern engines, so if you are really familiar with the fuel-injection electronics on these motors, I would love to hear more details.
sosmerc posted 06-03-2008 10:20 PM ET (US)
There is no substitute for the proper factory service manual as there are usually subtle differences from one model or brand to the next.
However, The idle speed can be adjusted on that engine without a computer. It involves careful synchronization of the throttle valves and a balancing tool is helpful. When you mess with the throttle valves you are also changing the voltage output to the engine computer from the throttle position sensor. Naturally there are specs for all the settings and again, you really need a manual to do the procedure correctly.
Marlin posted 06-04-2008 07:22 AM ET (US)
According to my SELOC manual (which is okay, but perhaps not everything one could wish for), the idle on this engine is adjustable by a set-screw on the throttle linkage arm.
You need to remove the intake runners (aka. "air silencer unit").
"Mercury also advises that while checking alignment of the [throttle linkage lever] mark you visually verify that the idle speed arm on the other end of the throttle linkage is against the speed screw. If you are unsure of the screw location, follow the link from the ball connector at the top of the throttle cam to the right (while looking at the powerhead) to the point where the link connects to the idle speed arm. The idle speed screw is the spring loaded screw threaded horizontally inward toward the powerhead and the arm. The screw is normally just beneath a small plastic cover."
The manual marks the complexity of this operation as "moderate - suitable for a DIYer with experience and a working knowledge of mechanical procedures"
-Bob
jimh posted 06-04-2008 08:03 AM ET (US)
It sounds to me like you adjust the idle speed with a screwdriver, not with a serial data connection using a computer terminal which modifies stored code in the algorithm of an engine control module processor.
itl posted 06-04-2008 04:13 PM ET (US)
Sorry, I was a bit unclear in my previous post.
I did not mention any serial data manipulation. As far as I know, it is not even possible in that engine, but if you know what you are doing, you can change the ECU software, but that is totally different story and require deep understanding about engine control unit and how everything works in that engine. Also you need proper equipments change the sw in ECU chips.
It is true that you can change a bit the idle speed by screwing the throttle link arm set screw in some engines, but that was not what I was referring. If set that screw you just change the throttle valve setting in throttle body, same thing if you change the position of your throttle control lever. However, there is predefined range for idle speed in ECU software and if you cant set idle correct by screwing that screw, then you have something wrong in your engine. You cant set EFI engine idle speed the way you do with carbs. But yes, I guess I was wrong when I said that you cant set idle by screwing a screw. Sorry for that.
Marlin posted 06-05-2008 11:10 AM ET (US)
I took a follow-up look through the SELOC manual for the 2001-2004 Mercury 115 4-strokes. The 2005-2006 should be similar, but are not covered by my manual. If anything, the answer about idle adjustment is a little less clear now than it was before.
I stand by my previous quote about the idle adjustment screw. However, it looks like itl is basically correct - normally the ECM controls idle speed by manipulation of the idle air control valve. The ECM appears to be a modestly sophisticated digital device, a judgement I'm making based on it's input and output devices, which include a manifold absolute pressure (MAP) sensor, a throttle position sensor (TPS), a crankshaft position sensor, fully electronic ignition, individual port fuel injection, and a diagnostics connector.
The 3-pin diagnostic connector appears to be identical in both the Mercury and Yamaha versions. One pin (white/black) connects directly to the ECM, and one pin (black) connects to ground. The third pin varies based on year and manufacturer.
In the 2001 Mercury, this pin (yellow/red) runs to the malfunction indicator lamp connector (the other feed to the MIL runs to the ECM) and then to the main relay; I'm guessing that line is +12VDC. I think the white/black pin is probably a serial connection to the ECM.
In the 2002-2004 Mercury, this pin (red/orange) runs to the main relay but also feeds one side of the dual ignition coils. Again, I'm guessing it's +12VDC. Also note that on the 2002-2004 Mercury, there is no separate malfunction indicator lamp connector, but the diagnostic connector itself is labeled "malfunction indicator lamp" even though it's identical to the 2001 diagnostic connector. For these years, I think the serial connection is deleted, and the malfunction indicator lamp ECM connection now runs directly to the diagnostics plug.
Finally, on the Yamaha version things seem to be identical to the 2001 Mercury, with an separate malfunction indicator lamp.
-Bob
jimh posted 06-05-2008 10:06 PM ET (US)
Thanks for the description of the sensors and the arrangement of the diagnostic port wiring. From your description the engine sounds like its control system is more sophisticated than I thought. And if there are only two or three wires in the diagnostic connector, then it certainly appears to be a serial data link connection.
I do not recall any accounts of the ECM firmware on these engines being field modified.

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Author	Topic: 2001 Mercury 115 FOURSTROKE EFI Idle Adjustment
rired	posted 06-02-2008 11:26 AM ET (US) Is there a way to adjust the idle speed on [a 2001 Mercury 115-HP EFI FOURSTROKE] motor? [I] was told that [engine speed] should be about 750-RPM in gear. With the throttle fully retarded [my engine idles] at 500-RPM.
Tohsgib	posted 06-02-2008 11:28 AM ET (US) The only way is to adjust the throttle is the cable itself at the engine. If there is no adjustment there then it might have to be done with a computer at the shop.
Tohsgib	posted 06-02-2008 12:16 PM ET (US) Adjust the cable at the engine a turn or [two].
Tohsgib	posted 06-02-2008 12:18 PM ET (US) My Suzuki really has no adjustment. You adjust the cable so it runs all the way to WOT and then the computer sets the idle. Not sure if yours is the same but can't hurt trying the cable, just make sure you are getting WOT when adjusted.
jimh	posted 06-02-2008 10:58 PM ET (US) These motors are actually Yamaha power heads bought by Mercury. (They bought 70,000 of them.) The fuel injection is probably from Yamaha, and I don't think it is particularly sophisticated, that is, you don't make adjustments to it with a computer--it does not have stored code or erasable memory.
itl	posted 06-03-2008 05:54 AM ET (US) You can't adjust idle speed of that engine or basically in any EFI engine without doing some magic to engine software. Idle speed is computer controlled. If it is not in correct range, then there is some problem in your engine. Typically the computer (ECU, EMM or whatever you call the engine control unit) adjust the idle stabilation valve based on information what it gets from various sensors (engine rpm, engine temp, maf/map etc). Idle stabilation valve then set how much engine gets air in idle speed, amount of air actually sets the idle speed in the range where it should be. That is the basic principle how idle is set in (any) EFI engine. Computer is continuosly checkin idle speed and if idle goes lower than it should then ECU opens the idle stabilation valve and if idle is too high then ECU closes the valve. Pretty simple actually. Typical problems with the idle speed are air leaks in manifold or somewhere else in air intake after amount of incoming air is measured or incorrect fuel adjustment.
jimh	posted 06-03-2008 08:19 AM ET (US) Are you saying that to make adjustments to all electronic fuel injected engines you have to connect a terminal to a serial data port and make changes to the stored algorithm which controls the functioning of the engine? This is at variance with my experience, as I have never heard anyone mention that a serial data connection exists on these Yamaha EFI motors to which one could connect a terminal. My impression of these Yamaha motor fuel systems is that the programming which controls them is fixed and the circuitry contains analogue techniques as opposed to being strictly in the digital realm and using stored code which can be field modified or re-programmed. I love to peak under the hood of modern engines, so if you are really familiar with the fuel-injection electronics on these motors, I would love to hear more details.
sosmerc	posted 06-03-2008 10:20 PM ET (US) There is no substitute for the proper factory service manual as there are usually subtle differences from one model or brand to the next. However, The idle speed can be adjusted on that engine without a computer. It involves careful synchronization of the throttle valves and a balancing tool is helpful. When you mess with the throttle valves you are also changing the voltage output to the engine computer from the throttle position sensor. Naturally there are specs for all the settings and again, you really need a manual to do the procedure correctly.
Marlin	posted 06-04-2008 07:22 AM ET (US) According to my SELOC manual (which is okay, but perhaps not everything one could wish for), the idle on this engine is adjustable by a set-screw on the throttle linkage arm. You need to remove the intake runners (aka. "air silencer unit"). "Mercury also advises that while checking alignment of the [throttle linkage lever] mark you visually verify that the idle speed arm on the other end of the throttle linkage is against the speed screw. If you are unsure of the screw location, follow the link from the ball connector at the top of the throttle cam to the right (while looking at the powerhead) to the point where the link connects to the idle speed arm. The idle speed screw is the spring loaded screw threaded horizontally inward toward the powerhead and the arm. The screw is normally just beneath a small plastic cover." The manual marks the complexity of this operation as "moderate - suitable for a DIYer with experience and a working knowledge of mechanical procedures" -Bob
jimh	posted 06-04-2008 08:03 AM ET (US) It sounds to me like you adjust the idle speed with a screwdriver, not with a serial data connection using a computer terminal which modifies stored code in the algorithm of an engine control module processor.
itl	posted 06-04-2008 04:13 PM ET (US) Sorry, I was a bit unclear in my previous post. I did not mention any serial data manipulation. As far as I know, it is not even possible in that engine, but if you know what you are doing, you can change the ECU software, but that is totally different story and require deep understanding about engine control unit and how everything works in that engine. Also you need proper equipments change the sw in ECU chips. It is true that you can change a bit the idle speed by screwing the throttle link arm set screw in some engines, but that was not what I was referring. If set that screw you just change the throttle valve setting in throttle body, same thing if you change the position of your throttle control lever. However, there is predefined range for idle speed in ECU software and if you cant set idle correct by screwing that screw, then you have something wrong in your engine. You cant set EFI engine idle speed the way you do with carbs. But yes, I guess I was wrong when I said that you cant set idle by screwing a screw. Sorry for that.
Marlin	posted 06-05-2008 11:10 AM ET (US) I took a follow-up look through the SELOC manual for the 2001-2004 Mercury 115 4-strokes. The 2005-2006 should be similar, but are not covered by my manual. If anything, the answer about idle adjustment is a little less clear now than it was before. I stand by my previous quote about the idle adjustment screw. However, it looks like itl is basically correct - normally the ECM controls idle speed by manipulation of the idle air control valve. The ECM appears to be a modestly sophisticated digital device, a judgement I'm making based on it's input and output devices, which include a manifold absolute pressure (MAP) sensor, a throttle position sensor (TPS), a crankshaft position sensor, fully electronic ignition, individual port fuel injection, and a diagnostics connector. The 3-pin diagnostic connector appears to be identical in both the Mercury and Yamaha versions. One pin (white/black) connects directly to the ECM, and one pin (black) connects to ground. The third pin varies based on year and manufacturer. In the 2001 Mercury, this pin (yellow/red) runs to the malfunction indicator lamp connector (the other feed to the MIL runs to the ECM) and then to the main relay; I'm guessing that line is +12VDC. I think the white/black pin is probably a serial connection to the ECM. In the 2002-2004 Mercury, this pin (red/orange) runs to the main relay but also feeds one side of the dual ignition coils. Again, I'm guessing it's +12VDC. Also note that on the 2002-2004 Mercury, there is no separate malfunction indicator lamp connector, but the diagnostic connector itself is labeled "malfunction indicator lamp" even though it's identical to the 2001 diagnostic connector. For these years, I think the serial connection is deleted, and the malfunction indicator lamp ECM connection now runs directly to the diagnostics plug. Finally, on the Yamaha version things seem to be identical to the 2001 Mercury, with an separate malfunction indicator lamp. -Bob
jimh	posted 06-05-2008 10:06 PM ET (US) Thanks for the description of the sensors and the arrangement of the diagnostic port wiring. From your description the engine sounds like its control system is more sophisticated than I thought. And if there are only two or three wires in the diagnostic connector, then it certainly appears to be a serial data link connection. I do not recall any accounts of the ECM firmware on these engines being field modified.