John-zuki High idle

[Starwindmango]

Hey everyone: I have a 1998 Johnson 70 HP four stroke which is virtually the same as a Suzuki DF70. This boat is new to me and I have two issues which may or may not be related:

The engine idles too high in the water: about 1000-1100 RPM, I believe it is supposed to be about 650. When I crank the engine, the check engine light comes on with a buzzer that sounds for about 10 seconds. The buzzer then goes off and the light stays on. I have read to clean battery terminals and will do that. The main issue is the high idle.

Also, when the ignition is turned to just the ON position, I get a 2-3 error code which I believe is the IAT sensor. Where is this located on the motor? This code could possibly be 3-2, but I’m 90% sure it’s 2-3.

Any help or Pictures from the owners manual would be appreciated!

Thanks,
Ryan

[Starwindmango]

Also:

Wanted to post one thing I noticed today when I went to do some other work on the boat: the motor idles at about 1100 RPM in OR out of the water on muffs. This seems odd that there is no idle change between the two. May indicate something. Any thoughts?

[Starwindmango]

No one?? This motor is essentially a rebadged DF70

[Murray]

My IAT (Intake Air Temperature) is located in the air intake silencer, port side, close to the starter. To test this sensor remove it and place in a pot of water, heat the water and measure the resistance between the terminals while heating the water. The resistance should drop as water temperature increases. Another thought, could you be having issues with IAC (Idle Air Control) valve?

To my understanding there is no idle adjustment per say. The sensors feed data in to the EMC and the EMC sets the idle as per incoming data. Poor/incomplete data in equals poor running engine.

Idle is idle, motor in neutral should rev. same whether in tub of water or muffs on. Idle should decrease as engine temperature increases.

Perhaps the real experts will chime in, there is a lot of communication between sensors/engine and ECM. A service manual will really help, especially with the specifications/test procedures.

Disclaimer: Above note is from 2009 DF90A service manual and I'm no expert.

[Starwindmango]

Thanks. I found the IAT sensor, will need to check it. On the IAC solenoid, I removed it and couldn’t tell if it would move or not. Any tips on testing that?

I’m surprised the idle in and out of the water would be the same. I would expect a few hundred RPM less at idle in the water.

I got a DF70 manual and am going through that now

[Murray]

The IAC valve should open and close by turning the key off and on.
With the valve out of the intake manifold you should be able to watch it open and close.

[redlowrey]

My IAT (Intake Air Temperature) is located in the air intake silencer, port side, close to the starter. To test this sensor remove it and place in a pot of water, heat the water and measure the resistance between the terminals while heating the water. The resistance should drop as water temperature increases. Another thought, could you be having issues with IAC (Idle Air Control) valve?

To my understanding there is no idle adjustment per say. The sensors feed data in to the EMC and the EMC sets the idle as per incoming data. Poor/incomplete data in equals poor running engine.

Idle is idle, motor in neutral should rev. same whether in tub of water or muffs on. Idle should decrease as engine temperature increases.

Perhaps the real experts will chime in, there is a lot of communication between sensors/engine and ECM. A service manual will really help, especially with the specifications/test procedures.

Disclaimer: Above note is from 2009 DF90A service manual and I'm no expert.

'''''''''''''''There is a base idle setting which is done at the factory and would be set around 500 rpm minimum throttle opening. You don't test the iat sensor by putting it in water, use a hair drier, test the temp sensor and exhaust temp sensor in a pot of water and heat it up to get a resistance change in the sensor.

The iac valve is just a two wire magnetic plunger type that is duty cycled by the ecu depending on operating conditions placed on the engine. When you turn the key to the start position the ecu will apply a full ground or 100% duty cycle to the valve and it will open to its maximum position. When the engine starts it will bypass enough air to keep the idle stable depending on operating conditions. If you test the valve your self off the engine with battery voltage, don't leave the ground connected very long other wise you will over load the solenoid.

[Starwindmango]

Thanks guys. I'll try to check the IAC valve this week. Hard to do since the boat is about 30 mins from my office and it's dark at 5:00 here. When I looked at the solenoid this weekend, I couldn't see that the plunger (I'm assuming this is the center hole) moved at all. This was of course without any power.

I purchased a new battery and will put that in to see if it eliminates the long beep and check engine light. From everything I've read, this symptom is caused by a weak battery, and I know mine is a few years old.

[Starwindmango]

Wanted to update this thread in case anyone comes across the issue in the future:

Took the boat to my local Suzuki dealer and they plugged it into the computer and were getting low oil pressure messages. They checked the oil filter and an incorrect filter had been put on by a previous owner. The passages were too small for the motor, causing the ECU to idle the motor at higher RPM to get the oil pressure it wanted. The dealer changed the oil filter to a correct one and cleared the codes and error messages went away and the motor has idled correctly since.

Cost me a couple hundred bucks to have them change an oil filter that I could have done myself, but an odd problem that they had seen before that I probably would have never found!

[redlowrey]

Years ago there was a show on tv called the sale of the century, well I think I have just read the con of the century, they said the ecu increased the idle because the ecu needed to get the oil pressure it wanted, how the f''''''' would the ecu know how much the oil pressure was, the switch is either open or closed.

After reading your first post your engine was idling at 1100rpm, if the throttle was closed and the closed throttle position switch was closed, your ecu will automatically apply 15% duty cycle to the iac and sound the buzzer, and then you would screw the iac bypass screw in the throttle body in to slow the idle down to around 700 rpm. Once you get the idle right, lift the warm up leaver or open the throttle and the ecu will cancel the iac fixed duty cycle.

I think who ever owned the boat before had some stalling problems and increased the idle to stop it stalling, we will see.

[Murray]

Ryan:

Glad you got your issue sorted out. Your first post was an error code due to high idle. Your last post was the solution, low oil pressure due to wrong filter. I would have thought the ECM would have given you a 5-3 code (Oil pressure switch). One of the conditions for a 5-3 code is a clogged oil filter which is what your issue was. Don't get me wrong, I don't doubt the dealer I'm just having a hard time wrapping my head around the initial code vs. the solution.

[Starwindmango]

Obviously the ECU knew something about the oil pressure as the error messages the dealer was getting when plugged into the motor was that there was low oil pressure. It wasn't like the idle RPM was wavering from 1100, it was fixed there every single time.

The last time they had seen this issue was with a John-zuki motor as well, using the same type of Sierra oil filter mine had.

I tried the Suzuki idle set procedure you described below. Did not clear the beep or fix the problem.

[Starwindmango]

Ryan:

Glad you got your issue sorted out. Your first post was an error code due to high idle. Your last post was the solution, low oil pressure due to wrong filter. I would have thought the ECM would have given you a 5-3 code (Oil pressure switch). One of the conditions for a 5-3 code is a clogged oil filter which is what your issue was. Don't get me wrong, I don't doubt the dealer I'm just having a hard time wrapping my head around the initial code vs. the solution.

I agree, I would have expected the 5-3 code as well, which is what puzzled me so much. That said, this motor is using older controls, but the tach does have the normal four Johnson/Evinrude warning lights. My understanding is that these John-zuki motors used the same type of error code system as their Suzuki counterparts.

[redlowrey]

Obviously the ECU knew something about the oil pressure as the error messages the dealer was getting when plugged into the motor was that there was low oil pressure. It wasn't like the idle RPM was wavering from 1100, it was fixed there every single time.

The last time they had seen this issue was with a John-zuki motor as well, using the same type of Sierra oil filter mine had.

I tried the Suzuki idle set procedure you described below. Did not clear the beep or fix the problem.

''''''''''''''Mate the only thing that your engines computer would see is zero volts or five volts, it cannot tell what's going on in between. If the oil pressure drops below 14 psi the switch contacts will close, the ecu will see zero volts and the oil pressure light will come on.

The only thing that can make our engine idle fast is incorrect adjustment of the throttle plate, an air leak, air bypassing the iac valve, incorrect adjustment of the iac bypass screw. So these people are telling you that the ecu could not sense oil pressure so it commanded the iac valve to bypass more air to get oil pressure, what would have happened if the oil pump failed, or low on oil, keep bypassing air till the rpm was at 2000 I don't think so.