" off idle stumble ", " surging ", " runs rough low rpm " issues..


Information and questions on GL1500 Goldwings (1988-2000)
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bbrackett
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Joined: Mon Oct 01, 2018 6:15 am
Location: Sedalia, MO
Motorcycle: 1988 GL1500

" off idle stumble ", " surging ", " runs rough low rpm " issues..

Post by bbrackett »



Hi Folks, I've read many posts about " off idle stumble ", " surging ", " runs rough low rpm " issues..
Here is a post that makes logical sense to me - viewtopic.php?f=6&t=9356

Folks have replaced fuel pumps ( local Honda Goldwing Guru 35+ yrs, said he has never replaced a fuel pump )
Folks have removed the fuel shutoff - this cured my fuel smell, wasn't leaking fuel but the diaphragm had a rip
SeaFoaming, Carb Rebuilding, Vac Hoses etc..

on the stand, in neutral, within 1-2 mins of starting, if you hold the throttle about 1500rpm, if you hear and see the RPMs bump up and smooth out then go rough again
it almost sounds like its running on 4-5cyls, what I found is that spark is dropping intermittently to all cyls

reading through an old post - viewtopic.php?f=6&t=9356
I'm sure the issue is the ECM.

my 1988 has ECU MT2DD 591B1 8523U and I'm going to replace with MT2DD 591B1 8613U
:-) I'll let you know and I can't wait to have the bike smooth again, it's sooo annoying.

Oh yea.. and the miss fire happens at all RPM, all gears.. it's just that 3-5th you can't feel it as much, but I can feel the bike surge a bit in 3-4th @ 2-3k rpms.

I'd love to send to someone to dig into the ECU maybe find better components ??


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Rambozo
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Re: " off idle stumble ", " surging ", " runs rough low rpm " issues..

Post by Rambozo »

Most people just want to throw parts at a problem. A lot of these bikes sit unused for long periods which is never a good thing. It can be hard for the home gamer to properly diagnose something like low rpm roughness or off idle stumble. A good oscilloscope and an exhaust analyzer make finding mixture and ignition issues pretty easy.
While some of the 1800s have ECU issues, you don't hear that about 1500s with the exception of burning out the fuel pump output transistor from a failing fuel pump.
bbrackett
Posts: 110
Joined: Mon Oct 01, 2018 6:15 am
Location: Sedalia, MO
Motorcycle: 1988 GL1500

Re: " off idle stumble ", " surging ", " runs rough low rpm " issues..

Post by bbrackett »

Here's some pics of the inside of the ECU






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ct1500
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Re: " off idle stumble ", " surging ", " runs rough low rpm " issues..

Post by ct1500 »

delete////////////??
Last edited by ct1500 on Wed Aug 31, 2022 4:53 pm, edited 1 time in total.
Local and need repair help with your 1500, Valkyrie or ST please click contact
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ct1500
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Re: " off idle stumble ", " surging ", " runs rough low rpm " issues..

Post by ct1500 »

bbrackett wrote: Mon Aug 29, 2022 8:00 am
Folks have replaced fuel pumps ( local Honda Goldwing Guru 35+ yrs, said he has never replaced a fuel pump )
I can believe that. There are dealer serviced and owner serviced machines. A Dealer will find and repair a fault. Owners will often take the cures in a can such as seafoam and dump a bottle into the tank. Nothing will kill a fuel pump faster than that kind of overdose which then the owner gets to replace and writes about on Forums without making the connection to a megadose.
bbrackett wrote: Mon Aug 29, 2022 8:00 am it almost sounds like its running on 4-5cyls, what I found is that spark is dropping intermittently to all cyls
Ignition systems on the 1500 are pretty much bullet proof, what procedure did you use to determine loss of ignition on all spark plugs?
Local and need repair help with your 1500, Valkyrie or ST please click contact
Nothing leaves my shop till its' perfect
This is what I do
bbrackett
Posts: 110
Joined: Mon Oct 01, 2018 6:15 am
Location: Sedalia, MO
Motorcycle: 1988 GL1500

Re: " off idle stumble ", " surging ", " runs rough low rpm " issues..

Post by bbrackett »

Plugs are good replaced gapped etc
plug wires good no signs of cross sparking
coils test good
connections good
pulse gens good
fuel good
fuel pump good pressure n flow
fuel shut off replaced was bad

fyi the pics of the CU were from the Carb Controller CCU not the Ignition CU was confused

disconnected and tested the pulse gens
within Honda spec for Ohm test

Reconnected road home and seems like the issue is resolved

40yr Honda guru said he has never changed a
fuel pump, has changed a “couple” times ICUs

Im going to disconnect the pulsers again at the RH fan, try cleaning the connections and ride it see what happens
bbrackett
Posts: 110
Joined: Mon Oct 01, 2018 6:15 am
Location: Sedalia, MO
Motorcycle: 1988 GL1500

Re: " off idle stumble ", " surging ", " runs rough low rpm " issues..

Post by bbrackett »

Disconnecting and reconnecting the pulsers at the RH fan helped but didn’t solve the issue

going to replace ICU in a couple weeks
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Happytrails
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Re: " off idle stumble ", " surging ", " runs rough low rpm " issues..

Post by Happytrails »

Would also mention there was recall for I believe 88-89 goldwing had to do with off idle stumble.

Sometimes the seafoam work good. Found that stabil 360 works better for this particular if bike sit for awhile. Good luck with the sorting :)


1991 GL1500 SE Anniversary Edition
Sun Flare Gold Metallic
Vallant Brown Inset
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