Suzuki 140hp 2012 stalling

[Bee888]

Hi All,

I recently installed a suzuki 140hp 2012 motor. The motor runs great, however I have been trying to diagnose a stalling issue.

At first run, it would stall when docking or shifting between forward, reverse, or after coming back to neutral from being under power. It would just stall, sometimes when turning the key after nothing happens. I would either have to wiggle the throttle or shift into forward/reverse and back into Neutral. I was then able to get it to crank again.

I have gone through most of the threads on here, and went down the path of adjusting the cable ends at the rear switch on the motor. Before adjusting, I could see there was some free play with the cable. I was able to play around with this and replicate my issue while at home on the driveway. I adjusted the cable end by screwing outwards, pushing the lever further back. All tests at home were good after this adjustment. Turn on, shift forward/back to neutral, turn off, fire up again no worries.


On second test run, it stalled while docking at the wharf, but didnt do it again the entire day. Coming back to Neutral after being under power was fine etc.

So it seemed my adjustments were good, but needed a little more. I then adjusted it a little more to push the switch lever on the motor further back until there was no more freeplay at all. Again all tests at home were good.

On the next run, as I was dropping in and started the motor it began to idle rough. It hadnt done this at all at home prior.

I know idling rough is usually IAC. However no alarms, no beeps nothing. While reversing off the trailer and away from the dock - motor stalled when coming back to Neutral. Then wouldnt start at all. The adjustments had made it worse! This makes no sense as there was no no freeplay at all.

I had to start shifting forward and back a few times to get it to finally start again. After this again ran all day fine.

Today I decided to adjust it back to where it was before this last change. This time i also manouevered the throttle cables running so there were no tight bends in the splash well. Shifting back and forth is ok, not much friction to indicate cables are bad. (They are 20 years old though as we kept my originals).

I am yet to test it again after this last change, but keen to get some info from the brains trust on this one. I dont think its IAC valve but cant say for sure. The fact it idled rough a little and then didnt for the rest of the day makes no sense.

What should i do if this doesnt work? Remove an clean IAC?

Thanks

[Moonlighter]

Sounds IAC related to me. There is a known issue on the 2012/13 115/140 A models with IAC’s failing and causing the engine ecu to be damaged

So if it was mine, I would immediately stop running the engine at all, replace the IAC, and pray that the ecu has not been damaged.

[Bee888]

Thanks Moonlighter. Guess its worth ruling out to be safe. I pulled mine off and it was a bit dirty but nothing crazy. I did notice the gasket underneath wasnt in very good shape, and one of the nuts holding it was loose. Possible airleak?

Anyway ill replace it to be safe.

I hear this part is the same as used on many car models and is usually around half the price from an auto parts store. Anyone have a link to a supplier in Syd?

Thanks in advance.

[Bee888]

Update for anyone following. Correction to my previous post - I realised the cable I had been adjusting was the clutch cable.

Replaced IAC and tested again. Motor still stalls when coming back to neutral from forward (deceleration). I was able to pin point the exact spot - It is in gear idle, with throttle full closed.

Took it home and followed the manual.
Tested for continuity at the ctp switch and found there was no continuity at the switch at that point. Adjusted the throttle cable now per manual and was able to get continuity all the way through in gear idle position at the ctp switch. Tested continuity the whole way through - now when throttle fully open, = none. When in gear idle = yes.

Took it out again and tested, this time left it on the trailer.
Put it into forward and open the throttle and tested coming back to neutral.

It stalled around the same point in gear idle but I really had to try fair few times of advancing throttle and backing off very quickly. When it stalled, throttle again was full closed, in gear idle.
Tested ctp switch again at this point to be sure - still had continuity.

Took it home again and tested continuity at both neutral switch inside rem control box and on block - both good in neutral. No continuity in gear as expected.

So my switch functions are good.

The confusing part now is, the next step is to check voltage at the switches - where do i check voltage for ctp? Is it the wire which plugs into it, or on the switch itself?

If the voltage is always 0 at both switches, apparently this is now an ECM failure.

I cant comprehend it being an ECM failure since the only time it stalls is the in gear idle position when decelerating and everything else is fine.

Any help is appreciated.

Will be sending it to the dealer soon to properly diagnose, but Syd lockdowns atm means I have all the time in the world to tinker.

[Bee888]

Unless, everything is now ok but i am causing the stall by advancing throttle hard and abruptly pulling back to neutral causing it to stall? Or should the motor never do that regardless?

[Moonlighter]

Unless you just want to throw parts and money at it, its time to get an experienced Suzuki mechanic who has, and knows how to use, the Suzuki SDS software, to hook it up and see what is going on. That is going to immediately show whether the ecu is damaged and if the IAC is the culprit, as might be suspected.

Throttling back quickly to idle presents no issues when the IAC is doing its job properly, its one of the tasks its there to do.

The longer you keep running it with a faulty IAC, the more likely it is becoming that the ecu is getting damaged.

[redlowrey]

No, that is why the closed throttle switch is there, to tell the ecu that the throttle is closed. When you pull the throttle back quick and the closed throttle switch is activated, the iac valve will bypass more air around the throttle plate and advance the timing a few more degree's to prevent a stalling condition.
The ecu will send 5 volts down that single wire and when the throttle is closed it will drop to zero, when the throttle is opened it will go back to 5 volts indicating to the ecu that the throttle has been opened.

The first thing you have to do is make sure that throttle can close all the way without any interference from the cable, get some carbi cleaner and clean the under side of the throttle plate, make sure that you have not adjusted the throttle plate at the stopper screw. run the engine till it gets hot and perform an idle adjustment procedure, this will fix the iac valve at 30% air bypass and allow you to adjust the idle speed via the idle speed air bypass screw, very important thing to do when you have idle speed and stalling problems.

Reading your first post I think there could be something else wrong, the iac valve uses duty cycle to control the speed at which the engine idles, if you understand what duty cycle means you will under stand what I am talking about.

[redlowrey]

Unless you just want to throw parts and money at it, its time to get an experienced Suzuki mechanic who has, and knows how to use, the Suzuki SDS software, to hook it up and see what is going on. That is going to immediately show whether the ecu is damaged and if the IAC is the culprit, as might be suspected.

Throttling back quickly to idle presents no issues when the IAC is doing its job properly, its one of the tasks its there to do.

The longer you keep running it with a faulty IAC, the more likely it is becoming that the ecu is getting damaged.

I didn't think you were going to reply to his post, If he has damaged the driver circuit on the iac vavle, we will find out when he trys to do an idle speed adjustment the ecu won't be able to fix the iac at 30% air bypass. What was happening in those early iac valves the windings were shorting sending too much current down the ground wire of the iac valve frying the driver transistors on that circuit, but you would think nine years later the problems would have been sorted, eg new iac valves or ecu's.

[Bee888]

Thanks Guys for the quick responses.

Moonlighter - IAC has been replaced now. I took your advice from my first post and Purchased it from the dealer and popped it in. So thats been ruled out. However issues still present.

redlowrey - I also think there is something else wrong. No idea how to do the idle adjustment and definitely think this is out of my league now. Id rather let the expersts handle it. Ill be taking this into Suzuki dealer as soon as lockdown is over and get them to take a look.

Will post an update once I have one.

Thanks for your help so far!

[Bee888]

I didn't think you were going to reply to his post, If he has damaged the driver circuit on the iac vavle, we will find out when he trys to do an idle speed adjustment the ecu won't be able to fix the iac at 30% air bypass. What was happening in those early iac valves the windings were shorting sending too much current down the ground wire of the iac valve frying the driver transistors on that circuit, but you would think nine years later the problems would have been sorted, eg new iac valves or ecu's.

IAC has been replaced.

[redlowrey]

Mate the driver is in the ecu, not the iac valve, when you turn the key on battery voltage will flow too and through the iac vlalve to ground inside the ecu when you turn the key to the start position the ecu will apply a full ground to the valve making the plunger retract allowing more air to bypass the throttle plate making the the engine run at a higher than normal idle, as the the engine warms up the ecu will start reducing the ground on the circuit by duty cycling it.

Do you know how to use a multi meter, if yes I can help you. If the circuit has been damaged I will tell you how to test it, as far as idle speed adjustment run the engine till it gets hot make sure the closed throttle switch is on I think for your engine turn the key to the start position five times when the engine is running and there should be a buzz from the buzzer and the iac valve will be fixed at 30%duty, engine rpm should be around 700rpm if not remove the rubber plug on the throttle body and adjust the rpm if it is not around 700 rpm turning clockwise will drop the rpm and anti clockwise increase rpm.
By the sounds of it you have a manual it will tell you how to do it.

You won't be going any where for a while gladis berijeclion wont let you out for weeks, We have dictator dan down in vic, But I am in regional vic so have some freedom, but I don't think it will be for long something will happen.

[Bee888]

Ah got ya, sorry thought you were talking about the IAC itself.
Yeah I have and know how to use a multi-meter, what do I need to do to test the circuit?

The idling is currently fine, on cold idles around 900 rpm and seems to drop to around 750rpm once fully warm. If the speed adjustment needs to be done, should I be doing this under load or on the muffs at home?

[redlowrey]

Ah got ya, sorry thought you were talking about the IAC itself.
Yeah I have and know how to use a multi-meter, what do I need to do to test the circuit?

The idling is currently fine, on cold idles around 900 rpm and seems to drop to around 750rpm once fully warm. If the speed adjustment needs to be done, should I be doing this under load or on the muffs at home?

If you had of posted that information in your first post, You would not have had to put an iac valve on the engine, we would have been able to see that the circuitry is still intact because you would not have been able to reach 900rpm, it would have been sitting at base idle, and not be able to drop to 750rpm. This is why you need to do a base idle test to see if the correct amount of air bypass is coming from the iac valve.
Run the engine on the muffs let it get hot in neutral, connect your volt meter up, black to ground and red to the single wire connector at the closed throttle switch, use a thin needle to push into the connector, there should be zero volts with the throttle closed and five volts with the throttle open key on or engine running.

To be able to set the idle the ecu needs to see zero volts on the closed throttle switch engine running, if it is turn the key to the start position 5 times engine running and if successful you will hear a beep, that means that the iac valve is fixed at around 25% if it is idling at spec leave it if not remove the rubber plug from the throttle body and adjust the rpm to spec then lift the warm up leaver to open the throttle it will beep and that is it.

[Bee888]

Yeah I was happy to replace the IAC regardless since it could cause ECM issues and I did have jumpy idling occur previously when I first posted.

My tests with the multi meter at CTP switch don't seem to match expected: This is what i got:

Disconnected CTP switch wire and popped pos needle inside spade connector, black to throttle body ground.

With ignition on and in neutral - 0v at the ctp switch, 6.30v at connector (g, r wire)
With ignition on and in either forward or reverse, throttle open - same results - 6.2 to 6.3 v at g,r wire..

So regardless of in gear or neutral, the CTP switch wire always has around 6v?

Did i test this correctly?, and if so i assume something else isnt right.

[redlowrey]

All you have done is checked the open circuit voltage, leave it connected and test it when the throttle is closed, it should pull the voltage to zero and when you open the throttle go back 5 volts.