IAC help on 2004 DF140 or the saga of Hard to Start and rough Idle

[jrfounta]

2004 DF140 4 stroke

This engine has almost no hours and spent most of it's life in storage at a mechanics shop following destruction of the boat it was on in 2005. I'll save the gory details but one of the mechanics apparently used it as his personal salvage yard, removing commonly failed parts for side work. I've traced down everything replaced/repaired/beaten into submission anything that wasn't working. Except the original IAC which was completely missing, a bad unit had been installed in its place.

I've replaced the IAC on the engine with a used unit. The solenoid checks at 10.x ohms which seems reasonable in my experience (but I've never dealt with a zuke before this one). When attached to an external 12v power supply the solenoid makes a definite click sound; but, I can't see any movement of the valve and I mean any

The biggest problems that lead me to believe that the IAC isn't functioning properly are:

In order to crank the engine I have to apply extra throttle and then very slowly ease the throttle down. Once the engine is warm I can move increase/decrease throttle rapidly as long as the engine isn't in gear.

A rapid decrease in throttle while in gear in the water (with no load the problem doesn't present itself) will cause the engine to die but crank right back up with nothing more than a quick turn of the key.

The IAC circuit supplies 13.x volts(battery voltage) when the ignition is turned on; however, when I connect the solenoid to the plug I can't hear/feel any click.

I've adjusted the idle RPMs to 650 after forcing the engine into fixed mode (hold >1000rps for >10s by adjusting the idle speed at the TB). There is zero change in RPMs after removing the engine from fixed mode. I've tried increasing the RPMs to 850 to see if the IAC will try to compensate; it doesn't at all.

Does anyone have any advice on testing these IAC valves? I can't drop $300 in the hopes that it is actually the valve and without buying a used unit that has actually made an engine run recently and properly I'm not sure I would eliminate my problem.

Any advice from zuke experts would be more welcome than I can tell you. At this point I would be willing to rent a functioning IAC just to see if it's the problem. I'm tired of telling my boys we'll go fishing next weekend...

Thanks for any help.

 

[99yam40]

Re: IAC (Idle air controller) help on 2004 DF140

Re: IAC (Idle air controller) help on 2004 DF140

no idea on zukes but Yamaha's are stepping motors not solenoids and if they stick it will burn out ECU on the controls of it.

Sounds like you need to pick up a service manual for your motor and see what tests it has

 

[jrfounta]

Re: IAC (Idle air controller) help on 2004 DF140

Re: IAC (Idle air controller) help on 2004 DF140

This Zuke is definitely a solenoid stepping motors are much easier to check. I've found some excerpts from the service manual and all they really offer is the expected ohm range. I would expect to see some physical movement when power is applied but maybe I'm mistaken. Thanks for the input 99yam40.

 

[99yam40]

Re: IAC (Idle air controller) help on 2004 DF140

Re: IAC (Idle air controller) help on 2004 DF140

I do not see how a solenoid could adjust anything as it would be open or closed, nothing in between.
key on 12V+ and ECU probably controls the ground if it is anything like Yamaha

 

[multimech]

Re: IAC (Idle air controller) help on 2004 DF140

Re: IAC (Idle air controller) help on 2004 DF140

I think you need to setup the engine at the base specs. It is helpful to have the Suzuki software to be able to test the solenoid duty. If you don't have that you are kind of in the dark. Unlike a carbed 4 stroke, there is not a dashpot that will keep the engine from dying out after a hard acceleration and then back to idle. I don't believe the IAC controls that either, except for having the air mix being at the level it needs to be for that throttle position.

Of interest. I worked on a Johnsuki the other day. Had and IAC problem. The IAC tested good on ohms, but the duty cycle on the test was not correct. I pulled it off and found a piece of crap in the throat of it. 99yam40 is correct. It isn't a solenoid. It is a stepper that actuates a valve that adjusts air flow into the intake.

 

[jrfounta]

Re: IAC (Idle air controller) help on 2004 DF140

Re: IAC (Idle air controller) help on 2004 DF140

Unfortunately I don't have the software, may wind up having to take it to a local mechanic. I'm very familiar with automotive engine systems and this is definitely a solenoid not a stepper. Just like the old ford iac solenoids that were on virtually every ford v8 from the 90s to early 2000's. They work with pulse width modulation to control the amount of opening and closing. I can't speak for any other model but this one just isn't a stepper.

I have returned the engine to its base specs my mention of other adjustments was just to illustrate that the engine isn't attempting to change the idle speed at all.

I'm not trying to shoot everyone down I'm just making sure we are on the same page and hoping to find an answer.

Thanks again to everyone giving me any input, it's a fair sight more than I've been getting locally.

 

[jrfounta]

Re: IAC (Idle air controller) help on 2004 DF140

Re: IAC (Idle air controller) help on 2004 DF140

Monday morning bump.

 

[clanton]

Re: IAC (Idle air controller) help on 2004 DF140

Re: IAC (Idle air controller) help on 2004 DF140

You don`t need the soft ware to set the idle. Clean the valve install, adjust the idle IAC the factory service manual. If the valve is bad will set a code in the tach. Count tach flashes for code.

 

[jrfounta]

Re: IAC (Idle air controller) help on 2004 DF140

Re: IAC (Idle air controller) help on 2004 DF140

You don`t need the soft ware to set the idle. Clean the valve install, adjust the idle IAC the factory service manual. If the valve is bad will set a code in the tach. Count tach flashes for code.

Thanks. I have all ready adjusted the idle to specs; however, the IAC doesn't seem to make any change in the idle speed after taking the engine out of fixed 15% duty. I can physically disconnect the iac power plug with no change in idle.

This motor is using a generic tach, no light to see. Is it possible to attach a light to see if any codes are being thrown? How would I go about wiring it?

Thanks for helping.

 

[jrfounta]

Re: IAC (Idle air controller) help on 2004 DF140

Re: IAC (Idle air controller) help on 2004 DF140

Anybody? I picked up a used solenoid that was pulled from a running suzuki esteem (same part # etc) I've installed it with no change. If I pass voltage to either solenoid with a standard 9v battery they both pull back equal amounts and return with no drag. However, when I attach the solenoid to the engine harness (it still reads battery voltage with the ignition switch in the run position) there is no movement in the plunger on either solenoid. I'm a bit confused as to why the the plunger wouldn't move unless the pcm is controlling the pulse width to stop plunger movement.

Someone out there must have some insight into what could be preventing the engine from attempting to engage the IAC when returning to neutral and cranking...

Thanks again for any help

 

[99yam40]

Re: IAC help on 2004 DF140 or the saga of Hard to Start and rough Idle

Probably control is on the negative if you have voltage at key on, still sounds like you need a service manual.
Should give steps and what equipment is needed for testing

 

[jrfounta]

Re: IAC help on 2004 DF140 or the saga of Hard to Start and rough Idle

I had a bit of an epiphany last night and decided to check something. I made up a harness so I could check voltages with the iac attached. When the iac is off the plug reads ~battery voltage indicating that the ecm is applying power to the circuit. When I attach the iac the ecm turns off the ground side of the plug. If I bypass the ground directly to the block the iac opens wide with no hesitation.

So why doesn't the ecm think the IAC needs to be activated? My guess would be that the ECM doesn't think the engine is in idle speed but why? My first thought was the CTP sensor but it ohms properly (all though there is a very minimal amount of resitance when open) I even removed the ground lead from the CTP switch and directly grounded to the block with no change. If not that why else would the ECM disable power to the IAC circuit (self preservation seems reasonable but ohms and amps pulled seem well within what I would expect from an activated solenoid).

If anyone has a little more knowledge of the logic used by the IAC and can direct me where to look I would appreciate it. If not, Yeah it may be time for me to track down a service manual. Sadly without diagnostic equipment(read computer) I'm not sure I'll be able to glean much more, long gone are the mercuries and evinrudes I once knew so well. Thanks again 99yam40

Whether or not I get an answer I will continue to update this thread with my trials and tribulations; maybe it will help someone else one day.

Thanks again to everyone that has offered any help.

 

[jrfounta]

Re: IAC help on 2004 DF140 or the saga of Hard to Start and rough Idle

The problem seems to be directly related to the PWM duty cycle that the ECM is calling for. I've adjusted the idle as called for by the manual (this procedure should set a 15% duty cycle), during the idle adjustment a multimeter indicates a duty cycle of 2.7%. Even when placing the engine back into normal operating mode the duty cycle remains ~2.x%.

With no IAC attached the duty cycle stays at a fixed 100% in all powered conditions (key on not running, key on running).

If I bypass the ECM ground the IAC opens wide enough to kill the engine with a rapid increase of fresh air. Rapid taps to ground can be used to increase idle speed. I'm confident the IAC is working as called for.

If anyone has any input on the reason for the extremely low duty cycle please drop it on me. If not just consider this another note in the learning process. Thanks.

 

[jrfounta]

Re: IAC help on 2004 DF140 or the saga of Hard to Start and rough Idle

One last bump to the top for advice before I break down and head to a shop. Surely someone has seen something similar to this before???

 

[dstumpe]

Re: IAC help on 2004 DF140 or the saga of Hard to Start and rough Idle

I too had an issue with a 2004 DF140 with the IAC valve. I did all the same tests and then replaced the valve with no resolution. I took it to the marina where they diagnosed the problem by swapping parts from another customer's engine. It turned out that the ECU was bad. It didn't show bad on the computer software but when the ECU was swapped out it purred. A new ECU at $1,500.00 fixed the problem. One other issue has cropped up after the ECU that has condemmed the engine. The motor was starting to misfire on the #4 cyclinder at idle and would take off when RPM's increased over 1500. A full disassembly showed salt water from the intake cooling water jacket was leaking into the intake and passing through the combustion process. The combined chlorides and exhaust gasses destroyed the exhaust passages and was allowing exhaust to enter the crankcase at the engine holder gasket, at full throttle it would pressurize the crankcase and blow oil out the top crankshaft seal. The salt in the gas also corroded the valves and the crankshaft as well. You would do well to at the very least, disconnect the intake manifold cooling jacket water hoses and thoroughly flush the jacket out to prevent this type of failure. I have a new DF140A now to repower after this failure and the engineers have removed this feature, along with the troublesome oil cooler (leaks caused by salt crystals displacing the o-ring seal) and also the fuel rail cooler. This tells me they knew of the potential or actual failures and have fixed it with a re-design.

 

[jrfounta]

Re: IAC help on 2004 DF140 or the saga of Hard to Start and rough Idle

dstumpe, you are spot on. I was actually logging to keep my promise and update the thread for others who might see it when I read your post.

I purchased software and cables to connect to the computer and was able to force 100% duty cycle at that point the resistance was still extremely high. Once I measured resistance of the ground with the 100% DC enabled and saw the extremely high resistance it all clicked. The manual says key on engine off should be 0% duty; however, I was registering a battery voltage. Once a load was applied (ie IAC) the voltage dropped to zero. I assumed this was the computer killing the relay once a load was applied, I was wrong. In fact the bad IAC the crooked mechanic (see post one about storage of this engine)installed was a dead short, when I attempted to crank the engine first time out I blew the ECM IAC relay, when the relay blew it stuck in a partially open high restiance position. So I had voltage that dropped under load with no change despite the ECMs attempt to reposition the IAC plunger.

After talking to a zuke/yamaha mechanic apparently the mitsubishi manufactured ECMs used in both engines are prone to this failure. His words were "not common enough the have to recall it, but common enough that I expect it, they really need to install a fusible link to prevent this from happening."

So does anyone have a used ECM for DF140 they want to sell? Hey I can even trade some Honda parts if someone were interested........