Stalling at idle and slight backfire


Information and questions on GL1200 Goldwings (1984-1987)
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mryan60
Posts: 30
Joined: Thu Jun 18, 2015 8:22 pm
Location: Caro, Micgigan
Motorcycle: 1985 GL1200L Limited

Stalling at idle and slight backfire

Post by mryan60 »



I need HELP! I had to replace the heads on my 1985 1200 Limited. I took care to make sure that the timing was set. When I put it all back together, it started and idled fine. I took it out for a test ride and noticed that my fuel consumption was down and but it seemed to be running fine. The next day, it wouldn't stay running unless I gave it a little throttle and I an occasionally getting a quiet backfire when I downshift. All plugs are firing has a new air filter and the fuel filter is good. A local shop suggested that it may be the ECU. Any suggestions will be greatly appreciated



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virgilmobile
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Location: Denham Springs,La.
Motorcycle: 1988 GL1500 I
Previously owned
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84 GL 1200 I

Re: Stalling at idle and slight backfire

Post by virgilmobile »

I tend to shy away from guessing and throwing expensive parts at a problem hoping something will magically fix it.
Diagnose the trouble and isolate the problem by test and eliminate.
Ok.Heads replaced and timing belts confirmed accurate.
Next test.Compression at wide open throttle.
You did change the heads...

Is the air cleaner OEM original or aftermarket.
Correct airflow is necessary.

Have you tried to run it with the gas cap loose.?

The control module is very robust but it does rely on very small voltage signals to keep it running well.
Disconnect the module..inspect for corrosion and plug it back in..A simple poor connection can upset the computer and fuel metering.

There's also other sensors that send signals to the module.Dual vacuum sensors,temp sensors,Throttle position sensor.etc.All sensors can be live measured for accuracy.

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virgilmobile
Posts: 9080
Joined: Sun Sep 19, 2010 5:39 pm
Location: Denham Springs,La.
Motorcycle: 1988 GL1500 I
Previously owned
78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: Stalling at idle and slight backfire

Post by virgilmobile »

One of her thought.Doesnt the module have "fault lights" on it?
Run the bike and before you turn off the key,look to see if any fault codes show.

mryan60
Posts: 30
Joined: Thu Jun 18, 2015 8:22 pm
Location: Caro, Micgigan
Motorcycle: 1985 GL1200L Limited

Re: Stalling at idle and slight backfire

Post by mryan60 »

There are no fault codes/lights. I will follow up on your other suggestions. Thanks!

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virgilmobile
Posts: 9080
Joined: Sun Sep 19, 2010 5:39 pm
Location: Denham Springs,La.
Motorcycle: 1988 GL1500 I
Previously owned
78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: Stalling at idle and slight backfire

Post by virgilmobile »

Do you have a digital or analog volt meter to test with?

mryan60
Posts: 30
Joined: Thu Jun 18, 2015 8:22 pm
Location: Caro, Micgigan
Motorcycle: 1985 GL1200L Limited

Re: Stalling at idle and slight backfire

Post by mryan60 »

Yes, I have an analog.

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virgilmobile
Posts: 9080
Joined: Sun Sep 19, 2010 5:39 pm
Location: Denham Springs,La.
Motorcycle: 1988 GL1500 I
Previously owned
78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: Stalling at idle and slight backfire

Post by virgilmobile »

Good.If your other attempts don't yeild the cause here's a couple of test points.
Do check the vacuum lines that feed the PB sensors.(2 each).
Locate the plug feeding the throttle position sensor.It has 3 wires.
With the bike running,measure between the green/blue (ground) and the red/white.You should see 4.75 to 5.25 volts.
This is a must for the computer to accurately determine fuel mixture.

mryan60
Posts: 30
Joined: Thu Jun 18, 2015 8:22 pm
Location: Caro, Micgigan
Motorcycle: 1985 GL1200L Limited

Re: Stalling at idle and slight backfire

Post by mryan60 »

On the throttle positioning sensor, I'm getting a 2.6 on green (ground) and light blue wire, 5.3 on the red w/white stripe

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virgilmobile
Posts: 9080
Joined: Sun Sep 19, 2010 5:39 pm
Location: Denham Springs,La.
Motorcycle: 1988 GL1500 I
Previously owned
78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: Stalling at idle and slight backfire

Post by virgilmobile »

I've never measured from the green to the frame,always across the two wires.I expect to see near 5 volt between them.
So if I could guess,if you measured between them (green and blue)you would have only 2.7 volts across the sensor.Not enough to supply a accurate signal to the module.
It sounds like a ground issue.
Inspect,clean and secure the ground points.
Battery lug.
Negative cable to the frame.
The module connections for corrosion on the green wire.
Any green wires that attach to the frame, especially near the module.

mryan60
Posts: 30
Joined: Thu Jun 18, 2015 8:22 pm
Location: Caro, Micgigan
Motorcycle: 1985 GL1200L Limited

Re: Stalling at idle and slight backfire

Post by mryan60 »

Thanks for all your help. I had no idea where to even start looking. I finally have it figured out. It was the connection was broken at the injector on #1 cylinder. Fix it and now it is running as it should.



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