Ignition Problem?

[wjbertrand]

Just keeping this thread alive with an update. Last night I pulled the throttle body assembly far enough out to access the TPS screws. The advice on the Honda car forums to cut a slot in the headless screws to remove them didn't work because they're made of cheese or something, stripped out immediately. This left me no choice but to drill out the screws (shudder). That done, the new TPS comes with conventional screws and fits perfectly. Tonight I will attempt the calibration procedure to get the voltage set to 0.48-0.50 volts, throttle closed, and 4.5 V throttle fully open. The TPSs have slotted holes to allow for adjustment. I measured the old TPS before disturbing it and found the voltages to be pretty close to this range. I recorded the numbers but the information is at home and I don't recall the exact values. Since the bike was running fine when cold, I figure these measurements are probably good.

I'll either get this fixed or screw it up beyond all hope! My fall back plan is to source a used throttle body assembly, including the TPS if my $15 fix fails.

 

[SupraSabre]

Just keeping this thread alive with an update. Last night I pulled the throttle body assembly far enough out to access the TPS screws. The advice on the Honda car forums to cut a slot in the headless screws to remove them didn't work because they're made of cheese or something, stripped out immediately. This left me no choice but to drill out the screws (shudder). That done, the new TPS comes with conventional screws and fits perfectly. Tonight I will attempt the calibration procedure to get the voltage set to 0.48-0.50 volts, throttle closed, and 4.5 V throttle fully open. The TPSs have slotted holes to allow for adjustment. I measured the old TPS before disturbing it and found the voltages to be pretty close to this range. I recorded the numbers but the information is at home and I don't recall the exact values. Since the bike was running fine when cold, I figure these measurements are probably good.

I'll either get this fixed or screw it up beyond all hope! My fall back plan is to source a used throttle body assembly, including the TPS if my $15 fix fails.

Jeff, I've got a couple of throttlebodies I've picked up from ebay. If you need one, let me know.

 

[wjbertrand]

Jeff, I've got a couple of throttlebodies I've picked up from ebay. If you need one, let me know.

Wow! Thanks, I will definitely keep that in mind. I should know, in the next day or two, if my fix on the cheap is going to work or not. There are three possibilities:
1. It works and the problem is solved
2. I screw it up so bad that I've created a new problem
3. I end up with the same problem, not being fixed after all that work!

In possibility #2 a replacement TB assembly might be needed.

 

[wjbertrand]

Update: There's both good and bad news to report. First the good news: The aftermarket Honda car TPSs works fine on the ST1300, they are electrically and physically identical. make sure to record the voltage outputs for your old TPS before replacing it so you can use them to calibrate the new TPS. The other option is to use the standard Honda spec of 0.45V throttle closed and 4.5V throttle fully open. This might be a good Wiki note if anyone ever needs to replace the TPS, though I suspect this will be extremely rare. Here's the one I used:

http://www.ebay.com/itm/201358243368?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT

The bad news is that the result is the #3 possibility from my post above - no change in the miss-firing problem at all. I tried running the bike at the troublesome RPM with my garage darkened to see if there were any arcs or leaks from the high tension leads of the coils, but there were no fireworks. I'm moving on to the coils as my primary suspect(s).

 

[Mellow]

I'm moving on to the coils as my primary suspect(s).

I mailed you my spare and the tracking shows it should be there Friday if not sooner.

 

[wjbertrand]

I mailed you my spare and the tracking shows it should be there Friday if not sooner.

Thanks a lot Joe, it it solves the problem, can I buy it from you?

 

[Mellow]

Thanks a lot Joe, it it solves the problem, can I buy it from you?

If it solves the problem you can have it.

 

[wjbertrand]

If it solves the problem you can have it.

I owe you a beer then at WeSTOC! Thanks, very generous.

 

[wjbertrand]

I mailed you my spare and the tracking shows it should be there Friday if not sooner.

Thanks Joe, if you meant last Friday, it never arrived.

 

[Mellow]

Thanks Joe, if you meant last Friday, it never arrived.

Looks like it got hung up with USPS - I'll PM you the link.. ugh!

 

[wjbertrand]

OK, thanks again Joe.

 

[wjbertrand]

Latest Update:
Thanks to Joe for the loan of a known good coil. Tried it on both the left and right sides with no joy, misfire problem remains. In addition to the coil test, I unscrewed each spark plug cap from its lead, snipped about 1/4" off and screwed the wire back into the cap, renewing the connections. I swapped out the fuel cut relay, inspected the cam position sensor and harness, disconnected and cleaned all 4 injector connectors. Disconnected and cleaned every connector I could access. I've inspected every inch of harness that I can see. Nothing looks suspicious.

The last idea I have is the fuel pump, but I'm bothered to explain the bouncing behavior of the tachometer needle when the misfiring occurs if it's the fuel pump though...

 

[bdalameda]

Since the tachometer uses the signal from the ignition to read rpm I am inclined to believe that the ignition circuit is at fault. Could be a bad pickup sensor (ignitor?) or ignition unit. Also I believe the St1300 uses a Knock sensor. I know a bad knock sensor can cause all sorts of ignition problems if bad. Crankshaft or Cam position sensors also can cause such problems.

 

[wjbertrand]

Since the tachometer uses the signal from the ignition to read rpm I am inclined to believe that the ignition circuit is at fault. Could be a bad pickup sensor (ignitor?) or ignition unit. Also I believe the St1300 uses a Knock sensor. I know a bad knock sensor can cause all sorts of ignition problems if bad. Crankshaft or Cam position sensors also can cause such problems.

Thanks, I tend to agree about the ignition circuit as a problem. I'm not sure what the "ignitor" is, there's nothing by that name in the wiring diagram or service manual. There are error codes for all of the sensors you mention and more, but I have no codes. I inspected the connectors and harnesses at all the sensors you mention and they appear pristine and normal. I hate to just start blindly replacing sensors.

 

[Blrfl]

I'm not sure what the "ignitor" is, there's nothing by that name in the wiring diagram or service manual.

All of the parts that run the ignition system are part of the ECM. He could mean the ignition pulse generator, which is the sensor plugged into the front of the engine just above the clutch housing. That is a part that could be affected by something mechanical and doesn't have an ECM fault code.

I'm really stumped here, Jeff. The next step for me would involve a lot of test equipment.

--Mark

 

[v8-7]

Maybe hot wire the 12v ignition direct to the battery to eliminate that as the problem.

It could be in parallel to the existing wiring , and connect as close as possible to the ecu to eliminate
as much circuity as possible.

 

[wjbertrand]

All of the parts that run the ignition system are part of the ECM. He could mean the ignition pulse generator, which is the sensor plugged into the front of the engine just above the clutch housing. That is a part that could be affected by something mechanical and doesn't have an ECM fault code.

I'm really stumped here, Jeff. The next step for me would involve a lot of test equipment.

--Mark

Yeah, I'm pretty stumped too, never had one this tough before. That sensor on the front of the engine is the crank position sensor. I've cleaned / inspected the connector and wiring that leads to it and there is a error code listed for it in the service manual.

Maybe hot wire the 12v ignition direct to the battery to eliminate that as the problem.

It could be in parallel to the existing wiring , and connect as close as possible to the ecu to eliminate
as much circuity as possible.

Not sure where to connect the extra wire when you say to the ignition. Are you referring to the ignition switch? Thanks.

 

[v8-7]

I will have to look at the schematic, but as far aft electrically as possible .ie, after the ignition switch, after the kill switch and after as much of the wiring harness as possible.

 

[Anna'sDad]

Yeah, I'm pretty stumped too, never had one this tough before.

Perhaps this is a good time to recap the problem, and the measures that have been taken.

I've attempted to distill the factual observations from the many pages of this thread as reported by Mr. wjbertrand:

• Motorcycle has 147,000+ miles, and was crashed & rebuilt.
• Engine stumbles/falters with steady throttle at 4,250rpm.
• Stumble/falter is not noticeable during the first 5 minutes of operation.
• Stumble/falter is not noticed when operating through the specific rpm range.
• Stumble/falter is independent of transmission gear selected.
• Stumble/falter is independent of vehicle speed.
• Tachometer needle drops to zero rpm, when engine stumbles/falters at specified rpm.
• Other than the tachometer, all other dash instruments remain operational.
• Exhaust output of both pipes sputter at the specified rpm range.

Additionally, I've distilled the various components that have been investigated, and found to not be at fault:

• Engine Stop Switch ? Clean & Inspect
• ABS Module ? Clean & Inspect
• Tachometer Circuit ? Inspect
• Ignition Coils ? Swap Out
• Battery & Ground Connections ? Clean & Inspect
• Throttle Position Sensor- Replace
• Engine Control Module ? Swap Out
• Side Stand Switch - Inspect
• Spark Plugs - Replace

The observation that the tachometer drops to zero, rather than coasting down with engine speed, leads me to believe this is an electrical issue. The bothersome piece of this puzzle is the unique rpm range where the problem presents.

Looking at the wiring schematic, I notice that both the Crankshaft Sensor, and the Camshaft Sensor share a common conductor (White/Yellow) from the ECM, presumably the voltage supply to each sensor. If this conductor were to have an intermittent connection, could that produce the symptoms that we're seeing here? But what would cause this intermittent condition at 4,250 rpm?

How about vibration? It's a possibility, though probably a remote possibility as far as the sensor conductor is concerned. What about a relay, a relay could become sensitive to vibration over time; back to the wiring schematic. The Bank Angle Sensor Relay, that relay provides +12vdc to a whole slew of engine components, including the fuel cut-off relay, all four fuel injectors, as well as both ignition coils. Now that could cause a problem if the relay contacts were sensitive to vibration.

I didn't see any reference to the Bank Angle Sensor Relay having been inspected, or replaced, I think it's worth a shot to swap the relay with one of the other relays. Yes it's a long shot, but too easy to ignore.

 

[Blrfl]

(Thanks, AD, for the summary. I went back and read the entire thread before dinner and had tried to stuff all of that into my head.)

That sensor on the front of the engine is the crank position sensor.

The manual refers to it as the IPG, but it's the same thing and you're right, there is a code for it (19) that I missed it when skimming the table.

The thing I'm down to with this is what's causing the ECM to intermittently not want to run the engine. If it isn't flaky power, it has to be in the one of the things that causes a no-start, which would be injectors, cam pulse generator, ignition pulse generator or any of the things on the no-blink list.

Everything but the injectors would be a cinch to run down with an oscilloscope.

--Mark