Hyosung GT650R EFI (Daewoo ECU) – Won’t hold idle / Stalling issue
- This topic has 11 replies, 2 voices, and was last updated 6 days ago by .
-
Posts
-
-
Bike Model = : GT650R
Hi everyone,
My name is Daniel and I’m writing from Poland. I recently got my hands on a fuel-injected Hyosung GT650R with the Daewoo ECU, and I’m dealing with a really frustrating idle issue.
Basically, the bike won’t hold its idle. About 90% of the time, I have to give it some throttle just to get it started, and the moment I let off the throttle, the engine dies. The weirdest part is that once in a blue moon, it will start up and idle perfectly fine as if nothing is wrong.
Here is what I have already checked and ruled out:
• TPS: Adjusted and set correctly to 1.12V.
• Vacuum leaks: Checked thoroughly, it’s not sucking in any unmetered air.
• ISC Valve: The idle speed control stepper motor is working.
Has anyone experienced something similar with these Daewoo ECU models? I feel like I’ve checked the obvious things, but I’m completely stuck. Any advice on what I should look at next would be greatly appreciated!
-
Would it be possible that your coils (on their own) or the HT Caps (problematic things) could be dropping out , wanning so that they fail & the bike cuts off ?
If the ISCV is truly working, have you tried a 2nd ISCV that is new so you can fully rule it out?
Can it ride in general (besides the idling issue?)
I am suspicious of either the stator pickup coil (wanning/haywire) or engine HT Leads+Coils or the ISCV unit.
I am not sure about injectors yet not unless your plugs are sparking dry / lean ? or fouled up bad ?
Grab yourself another set of new HT caps and coils to be sure (Stator , not sure yet but keep that in mind, usually if the stator-pickup coil goes at any point, so does everything on the bike and bike shuts off as it depends on it, the ECU checks that 1st)
I cant remember what the code is on Daewoo as its been a while , but on my Delphi if the ECU thinks my stator is suspicious , it sends a FI light with flashing sequence to translate to “pickup coil / no signal or pickup coil / noisy” etc and bike didn’t start till i replaced it but if it did start, i would see crazy jumps on the RPM meter then it dies.
-
To answer your questions and give you a bit more context:
• Coils and HT Caps: I haven’t checked the coils or the caps yet
• Pickup Coil (Stator): Is there any way to test or measure the pickup coil with a standard multimeter? If so, do you happen to know what resistance or values I should be getting?
• ISCV: I actually have a second, spare ISCV. I tested both of them and they behave exactly the same way. That’s why I concluded that they are working properly. If it helps diagnose the issue, I can take the stepper motor out, turn on the ignition, and record a quick video showing exactly how it moves.
• Spark Plugs : I completely forgot to mention in my original post that I just replaced the spark plugs with brand new NGK CR8E. When I pulled the old ones out, they had a heavy, black carbon buildup on them (they were fouled up black).
Other than the idle issue, the bike rides perfectly fine. As long as I hold the throttle open just a little bit, it won’t stall.
-
Hmmm “as long as you hold the throttle a little bit, it wont stall” , right here, i would quickly double check your butterflies in the throttle bodies did not get modified ? and try this , disconnect the ISCV and manually connect 2 fresh hoses from intake pipes to the airbox , see if idle improves ?
Then we can confirm if it was the throttle body , but also if you managed to remove the throttlebodies, replace the O-rings under them to stop any small air leaks or spray carb cleaner there to see if revs rise or change?
Stator, Coil, Caps = Check this link below and look for my reply that tells you how to test them with a multi meter (Ignore that it says GT125, the testing method is the same for its 650 sister)
Rectifier – How to Test Stator , Battery , Regulator – GT125R Carby
-
When I disconnected the ISCV and bypassed it manually with fresh hoses from the intake pipes directly to the airbox, the bike started up perfectly and held the idle RPM smoothly without me touching the throttle. However, as soon as I hooked the ISCV back up and assembled everything back to normal, the stalling problem returned immediately.
I also checked the physical movement of the stepper motor. When I flip the red kill switch on the handlebar to the “ON” position, the motor extends. When I turn it off, it seems to reset its position – it retracts and then extends again. So mechanically, it appears to be moving and working correctly.
I also checked everything else you mentioned, and it all looks good.
-
-
I just checked the continuity of all the wires going from the ISCV connector directly to the ECU with a multimeter. Every single wire beeped, so the wiring harness is perfectly intact and there are no broken wires.
This is my ECU. Do you think it’s broken? Is there any way to check it?
-
You have the mega, mega, mega rare Japanese made ECU by Mitsubishi Motors , I hope it is not fault , but because it is rare , If i were you i would check ebay US and eBay EU for this exact ECU as a backup. (I would trust this ECU or Delphi over any Daewoo ECU as Daewoo Era of Hyosungs had a lot of ECU failures)
If you have a Mitsubishi system on the bike, i would look after it.
If every single thing has been checked on the bike, then I will assume it is the ECU as your last thing to check. No proper way to diagnose it unless it gives error codes itself on the dashboard (service manual = mitsubishi era , will let you know how to get error codes) , if no error codes come, hunt a spare ECU.
If the ECU is not found at all, then have a think and see if there is a very cheap 650cc that was in an accident but electrics intact, get DELPHI as they are more present than the Japan ECU models.
Sorry I don’t have a very good answer to your problem as this is making me assume it is the ECU next. It’s weird how it works without ISCV attached but engine runs normally when riding, so strange, i don’t hear too much issues with Mitsubishi ECU models.
-
Man, thank you so much for all your help! Your advice has been incredibly valuable, and I’ve really learned a lot from this thread.
Just out of curiosity – if I eventually decide to swap the entire wiring harness to the Delphi system, is it a simple plug-and-play swap (just replacing the harness and the Delphi ECU), or will it require some extra tweaking, splicing, or custom modifications to make everything work with the rest of the bike?
-
Delphi System = stator and flywheel changed,
Delphi Coils (uses special plugs on harness that accept delphi only)
Harness + ECU
Iscv + injectors (newer black ones) + lambda sensors (delphi) + the sensors around your intake / airbox
Dash stays on bike its already EFi supported for various ECUs
Those are the main hurdles for conversion
-
I’m considering whether to change it to a Delphi or just buy a new Mitsubishi computer. Now I’ve noticed that the time also resets on the clock. If I turn the ignition off and on immediately, it remembers the time, but if I turn it off and wait 5 minutes, after turning it on again, it resets to 12:00. It also takes a very long time to load the fuel quantity, as if the bar was loading, it doesn’t show immediately, it takes about 30 seconds to show the correct quantity.
does this symptom also indicate a damaged ecu?
-
Fuel Level Reading = Normally, sometimes my 2005 GT took 10mins to get levels ready , then the bars started climbing up. The RC EFi model will flash empty for a little bit then get readings once it settles.
If the sensor is dead = it wont say anything all day. It doesn’t need ECU as fuel sender goes straight to dashboard via yellow wire (if i remember correctly?)
Hyosung either used capacitors or soldered battery on the dash to remember clock time, but after many years it stops , so counter always resets. It never bothered me to fix it as i just look at the phone or my wrist for true time haha.
Delphi vs Mitsubishi ECU is up to you , whichever is a cheaper or quicker route for you!
-
- You must be logged in to reply to this topic.