To low idle speed

[peos42]

Hi

This is my first post. I am new to this forum

I have, just like that, starting to get problems with my Suzuki DF140A 2014. To low idle rpm. The fault came instant. The engine runs fine, but just has to low idle. Pull throttle off to quickly and it dies.

Problem:
I during a ride a couple of days ago pulled off the gas from 15-20 knots (to neutral and idle) and the engine died and refused to start again. If I lift up the “warm up handle” and add some gas the engine starts and run fine on idle. The problem is that you can’t put in forward or reverse gear with that handle lifted. So the engine simply have to be able to run on idle with the “warm up handle” in down position to put in a gear.

I have now noted that if I run the engine warm with the “warm up” lifted and some gas, then I can sloooooowwly (if to quickly it dies) lower the handle and the engine stay on a very low idle (550-600 rpm) so I can put in a gear. According to the Suzuki service manual the idle rpm should be 700-750. So the idle rpm is way to low now (was higher before the problem came). Because of that the engine refuse to start without the “warm up” handle.

On my motor there is no idle rpm adjustment screw or any way to adjust idle. At least nor without a computer an Suzuki specific software.


What have I done:
I have removed the IAC valve (Idle Air Control) and cleaned it with throttle body cleaner. I forgot though to easy the impedance (should according to service manual be 8-12 ohm). The cleaning made no difference though…


Question:
Pone that the IAC valve is completely dead.. I put my thumb in the hose that takes in atmospheric air. Did not notice anything at all though on the motor idle rpm. Like that the valve is fully closed and there for need no air in. Anybody that knows if this valve should actively regulate the idle and this low idle rpm I have is because of a dead valve?


Or any other idea? Anyone?

(No water in water separator. And as it runs fine at full speed, I have therefor concluded that the fuel line to the engine is ok. As it is an injection engine and has no carburator with nozzles to clean, my brain has locked into the IAC valve)


Many thanks in advance

//Peo

 

[peos42]

Hi

This is my first post. I am new to this forum

I have, just like that, starting to get problems with my Suzuki DF140A 2014. To low idle rpm. The fault came instant. The engine runs fine, but just has to low idle. Pull throttle off to quickly and it dies.

Problem:
I during a ride a couple of days ago pulled off the gas from 15-20 knots (to neutral and idle) and the engine died and refused to start again. If I lift up the “warm up handle” and add some gas the engine starts and run fine on idle. The problem is that you can’t put in forward or reverse gear with that handle lifted. So the engine simply have to be able to run on idle with the “warm up handle” in down position to put in a gear.

I have now noted that if I run the engine warm with the “warm up” lifted and some gas, then I can sloooooowwly (if to quickly it dies) lower the handle and the engine stay on a very low idle (550-600 rpm) so I can put in a gear. According to the Suzuki service manual the idle rpm should be 700-750. So the idle rpm is way to low now (was higher before the problem came). Because of that the engine refuse to start without the “warm up” handle.

On my motor there is no idle rpm adjustment screw or any way to adjust idle. At least nor without a computer an Suzuki specific software.


What have I done:
I have removed the IAC valve (Idle Air Control) and cleaned it with throttle body cleaner. I forgot though to easy the impedance (should according to service manual be 8-12 ohm). The cleaning made no difference though…


Question:
Pone that the IAC valve is completely dead.. I put my thumb in the hose that takes in atmospheric air. Did not notice anything at all though on the motor idle rpm. Like that the valve is fully closed and there for need no air in. Anybody that knows if this valve should actively regulate the idle and this low idle rpm I have is because of a dead valve?


Or any other idea? Anyone?

(No water in water separator. And as it runs fine at full speed, I have therefor concluded that the fuel line to the engine is ok. As it is an injection engine and has no carburator with nozzles to clean, my brain has locked into the IAC valve)


Many thanks in advance

//Peo

Yesterday I checked the IAC. It was faulty. 0.2 ohm (i.e short). I came over a fresh used one for half the price of a new one. That used part had correct impedance (8-12 ohm) and 12v connected to it activated it. Check ok...

I mounted it, but the idle rpm was still way to low. I tried to put my thumb in the air hose and did not notice any reaction from the engine. Now the IAC is ok. But I think maybe the signal out from the ECU to the IAC is bad. So the IAC act like it is still dead.. I.e I think I need a new ECU.

So I think when the IAC broke, it created a short instead of an open circuit that made the ECU fail. I guess the ECU will still be ok on an engine if an IAC fail to an open circuit, but will toast the IAC signal out in the ECU if it short circuit when fail. REALLY BAD ECU DESIGN if an ECU can go bad when an external valve fails. Suzuki should have put a fuse in this circuit or have current limiting built in to the ECU.

My engine is 2014 and this happened 2023. Only 300 engine hours. Anyone that thinks Suzuki can take this on goodwill or warranty after 9 years years? The ECU version is 33920-92JB0

//Peo

 

[99yam40]

ECUs can be damaged by a stuck IAC also,
the ecu keeps trying to adjust the idle and overheats the internal ecu circuit.

you can try to get them to help, but I would not expect them to

 

[brodmann]

All you can do is look for a possible donor motor and look up the part numbers and see if they are the same. Should be pretty easy to do with lots of different parts websites to look up all the part numbers.

 

[flyingscott]

Take it in and pay for the scan. The parts cannon will get expensive fast.

 

[brodmann]

In reading up a little on your motor, I see it's a very common problem, with no real solution. The ECU reads input from sensors and sets the idle speed accordingly. The technicians can't bypass or modify the programming of the idle speed. I read where if you scream and holler enough, and the technician is savvy enough, he may be able to contact the manufacturer and be given a work-around for increasing the idle speed. That's just what I've read online from others with the same problem.

 

[KJM]

You need to take it to a dealer,IMO. You are assuming the ECU is damaged, but it could be something unrelated. You need to verify the problem before trying to replace things that may not need replacing. As said above that can get expensive real quick and leave you still with the original problem.

 

[lakensea]

STOP TRYING TO FIX IT YOURSELF. Take it to a reputable, experienced dealer.