Loss of power - unusual coloring of catalytic converter?

[dduelin]

This is your problem. Happened to me about a year and a half ago. I replaced the coil on the side where the pipe turned blue only because I had two spares that I had lying around. I'm 99% sure though that the problem was really due to an intermittent low voltage connection at the coil, i.e., loose spade connection on one of the two wires. If you were to look at your fuel consumption during the time that the misfiring is occurring you would see that your mpg figure drops almost in half...

I didn't mention it earlier but I did note the instantaneous MPG read out dropped to 16-17 mpg during the longer event. Just before that event I was playing around with trying to hit 51 mpg by slowing to a steady 55-57 mph. As soon as the event cleared up and things returned to normal the mpg shot back up to around 50 mpg.

I would prefer to splice in a new spade connector and boot rather than repair the torn one but those wires come right out of the main harness with no disconnects visible although the wiring diagram shows 2 pin connectors for them...they must be buried down in the main loom. I'll need to cut one off a donor bike if I can find one. This coil is on the left side that did not discolor, I tend to believe that coil went down momentarily and with it cylinders 1 & 3 causing 2 & 4 to carry the entire load which shot up their exhaust gas temperature and discolored the catalytic converter on the right side.

FWIW the black/white low voltage coil wire also connects to all 4 fuel injectors, the fuel cut relay, bank angle sensor, the fuel system solenoids, the ECU and the O2 sensors. Not being an electrician I could be wrong but if this wire grounded completely it would shut off the bike down immediately but if the one lead at the coil went intermittent it would only affect cylinders 1 & 3 from receiving ignition spark. The engine would continue to run as a twin on 2 & 4 and fuel would continue to be supplied to the dead cylinders 1 & 3 causing a smell of raw fuel that I did smell.

Thanks for all the replies.

 

[vinny]

Dave, if the connector boot was cut, but the spade terminal itself is not damaged, why not just "re-tighten" the female end of the spade connector and leave the boot taped. Take it out for a similar ride and see if the problem reoccurs. Expansion and contraction of electrical terminals is common when there is an increase in resistance and the resultant heat build up. The coils probably don't draw enough current to cause the original problem. I think the original problem could be related to vibration gradually loosening the connections. To re-tighten the connector, just squeeze it gently with a pair of pliers and reinstall... or just nix the connector and install a new one... no need to waste the wire. Just my 2 cents worth.

 

[Igofar]

 

[dduelin]

Dave, if the connector boot was cut, but the spade terminal itself is not damaged, why not just "re-tighten" the female end of the spade connector and leave the boot taped. Take it out for a similar ride and see if the problem reoccurs. Expansion and contraction of electrical terminals is common when there is an increase in resistance and the resultant heat build up. The coils probably don't draw enough current to cause the original problem. I think the original problem could be related to vibration gradually loosening the connections. To re-tighten the connector, just squeeze it gently with a pair of pliers and reinstall... or just nix the connector and install a new one... no need to waste the wire. Just my 2 cents worth.

The connection onto the coil was not loose........The female terminal required gently prying off of the male spade on the coil.......it was very tight as were the other 3.

Because the actual crimp connection of the wire to the female terminal was suspect and unseen I was able to slip the boot up far enough to inspect it (good) and I repaired the boot with some heat shrink tubing. I checked the MIL memory for any stored codes and there were none so I just put it all back together.

 

[Al Gully]

So the question still out there is,
Do you still need a new coil.

Also, is there a proven way to test the coils.
Sounds like you got your money's worth out of them with the mileage on your bike.

 

[Reginald]

I had a car that ran this way once. It left no codes during the failures. The shop had to drive it around for a couple of hours with a computer hooked up to capture the failure. Turned out to be an intermittent timing sensor failure. Could a sensor like the exhaust or oxygen sensors on the discolored side be failing? These sensors could run that side very lean and heat up the exhaust so that it discolored. Just a thought.

 

[Art Franz]

Had the exact same problem a few years back. It started about 1500 km from home (of course). The dealer suggested to disconnect all the farkles. I pulled all the fuses, and it ran perfectly for the rest of the trip. In the meantime, I reconnected the farkles one at a time. Turned out the culprit was the Audiovox cruise system. Ruined the finish on both pipes.

I'd had more trouble with the Audiovox system than it was worth so I took the whole thing out when I got home and put on a Breakaway throttle lock. Never a moment's trouble with that. Really love a cruise system when it works, but I think I'll wait till I get a bike with it factory installed.

 

[gsforster]

I would say that based on the symptoms you describe (misfire common to one bank only, one cat overheated) that you have an ignition misfire issue in that bank, and if it were an input problem it would be a random misfire not common to either bank. The cat got hot from burning raw unburned fuel from the 2 dead holes, simple as that. There was no combustion in that bank but normal fuel/air volumes. The efi system on the ST is fairly primitive in that it does not have the ability to monitor for misfire, so likely would not code. Your ignition coil on the affected bank most likely has an internal carbon track and the high kv is arcing to ground before the plugs, or is arcing to the primary circuit killing both cylinders at same time (waste spark setup). You coul duse a coil tester to check the kV output and compare to other coil, I'll bet you the bad one can't produce anywhere near what the good one can. But I think you have enough evidence to replace the coil for what it's worth.

 

[dduelin]

I would say that based on the symptoms you describe (misfire common to one bank only, one cat overheated) that you have an ignition misfire issue in that bank, and if it were an input problem it would be a random misfire not common to either bank. The cat got hot from burning raw unburned fuel from the 2 dead holes, simple as that. There was no combustion in that bank but normal fuel/air volumes. The efi system on the ST is fairly primitive in that it does not have the ability to monitor for misfire, so likely would not code. Your ignition coil on the affected bank most likely has an internal carbon track and the high kv is arcing to ground before the plugs, or is arcing to the primary circuit killing both cylinders at same time (waste spark setup). You coul duse a coil tester to check the kV output and compare to other coil, I'll bet you the bad one can't produce anywhere near what the good one can. But I think you have enough evidence to replace the coil for what it's worth.

Thanks, I do have two coils and HT leads in transit.

 

[gsforster]

Hope it helps, keep us posted......

 

[dduelin]

I would say that based on the symptoms you describe (misfire common to one bank only, one cat overheated) that you have an ignition misfire issue in that bank, and if it were an input problem it would be a random misfire not common to either bank. The cat got hot from burning raw unburned fuel from the 2 dead holes, simple as that. There was no combustion in that bank but normal fuel/air volumes. The efi system on the ST is fairly primitive in that it does not have the ability to monitor for misfire, so likely would not code. Your ignition coil on the affected bank most likely has an internal carbon track and the high kv is arcing to ground before the plugs, or is arcing to the primary circuit killing both cylinders at same time (waste spark setup). You coul duse a coil tester to check the kV output and compare to other coil, I'll bet you the bad one can't produce anywhere near what the good one can. But I think you have enough evidence to replace the coil for what it's worth.

So I got it backwards? The overheated cat was on the side of the engine with the dead cylinder(s) and not on the side that remained running? Can I use my multimeter to run the service manual test on the coils to check for 100V minimum to verify the bad one? I was going to replace both but if I can ID the bad one I'll save the other as a spare. Thanks!

 

[v8-7]

Auto Zone and other parts stores will check the coils for you .

I'm not sure what they use to check them, but it's worth checking out .

Sometimes the failure is heat related and won't show up on a static test .

 

[dduelin]

Auto Zone and other parts stores will check the coils for you .

I'm not sure what they use to check them, but it's worth checking out .

Sometimes the failure is heat related and won't show up on a static test .

Thanks Stan.

 

[gsforster]

So I got it backwards? The overheated cat was on the side of the engine with the dead cylinder(s) and not on the side that remained running? Can I use my multimeter to run the service manual test on the coils to check for 100V minimum to verify the bad one? I was going to replace both but if I can ID the bad one I'll save the other as a spare. Thanks!

Yup, the side with the overheated cat is most likely the misfiring side. You might be able to check that coil with a regular inline spark tester - the kind with the adjustable airgap knob. I think a coil that can jump something like a 3/8" gap equals 25kV or so, and would likely be bare minimum. I don't know specs off hand would have to look it up. You can measure coil primary and secondary resistances as per manual, compare the good side measurements and you might see some difference, but if coil has a carbon track burned inside this wont show up on a resistance test. A scope is the only way to find this. It is also possible that the ecm driver transistor that grounds that coil is going flaky, and you would need to verify that you have coil control when the misfiring is occuring. (dwell) . The reason the cat gets overheated is that during misfire, there is no combustion in the cylinder, so all that air along with the unburned fuel goes out the exhaust. The Oxygen sensor "sees" all this oxygen in the exhaust and responds by sending a low voltage (lean) signal to the ecm. The ecm responds by (you guessed it) increasing injector "on" time in the misfiring bank to add even more fuel to the dead cylinders. This makes the cat work ever harder to burn that fuel up and eventually destroys itself. In a car when the Check Engine Lamp flashes, this is what is happening.

The fact that the cat went blue seems pretty good evidence that you are still getting fuel so really narrows it down to ignition issue.

 

[dduelin]

OK, I know the coil sends a high voltage field to ground through the spark plug but are the coils otherwise grounded to the frame by the mounting bolts that pass through the bosses on either end of the ST1300 coil?

Update....I've put about 1300 miles on the bike since swapping the original coils out with a pair I bought and it has run perfectly since. In fact, with the new spark plugs and new used coils it seems to be getting about 10% better fuel economy than it was before the loss of power event. I can't explain that but I documented it with the last three tanks. Maybe it's summer blend fuel but whatever Red Bird is running as good or better than ever.

Like to know about the coils though.

 

[Doodaa]

Hope you have identified the coil you suspect is defective. Have you located an Auto Zone in your area for testing them ?

 

[Scooter]

OK, I know the coil sends a high voltage field to ground through the spark plug but are the coils otherwise grounded to the frame by the mounting bolts that pass through the bosses on either end of the ST1300 coil?

[-]Yes it is. Look at the schematic shown on page 20-2 of the service manual (2003 edition) that shows the ground connection to the coil. It can only be going through via the coil mounting bolts. Did you have any corrosion on your mounting bolts???[/-]

EDIT: After further reflection, I think I'm mistaken. See post below...

 

[dduelin]

Thanks for that Scooter. I had been looking at the schematic in the back of the manual and it does not show the direct ground just the ground through the spark plugs.

Now that I know the low voltage primary circuit goes to ground through the mounting bosses I think corrosion on the mounting bosses was the problem. When I got the new used coils I examined them and noted the right hand coil had slight rust staining on the rear most boss and I noted "I wonder if the OEM right hand coil for cylinders 2 & 4 has rust stains like that?". This is what I found.....the original RH coil had a lot of rust and the rust pitting had pretty much destroyed the smooth metal finish the bosses have when in good condition. The LH side does not have the SS U-shaped clip washers and the LH mounts were in original good condition. The washer must be a different alloy of stainless and the combination of heat and electro galvanic corrosion from dissimilar metals causes the RH mounts/grounds to rust.

I cleaned and buffed up the new used one before I installed it.

If you have a high mileage 1300 you might want to check the coil mounting bolts for corrosion that may cause the coil to quit working under the "wrong" conditions.

 

[dduelin]

This is what a good one should look like. This is the OEM LH coil - it does not use the U-shaped double washer.

 

[Scooter]

Thanks for that Scooter. I had been looking at the schematic in the back of the manual and it does not show the direct ground just the ground through the spark plugs.

Dave, after further thought I decided to go and measure one of my spare coils. Both the primary and secondary coils are isolated from the laminated core so in retrospect, it shouldn't matter if the core is grounded to the frame or not. I will test this out later next week since I have to take off my mid-cowling anyway for some other issues and it would easy enough to see if the bike runs when the coils are removed from their mounting points. That schematic from the service manual that I referenced earlier (pg 20-7) is in error. There is no ground connection going to the coil in the main wiring diagram shown in the manual.

I have also seen that same corrosion on the old coil that I removed off of my bike last year...