Intermittent problem - VTXOA
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post #1 of 20 (permalink) Old 10-25-2019, 09:48 PM Thread Starter
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Intermittent problem

I have on '03 VTX1800S, all stock (now). Last year my bike started cutting out on me. It started out feeling like an occasional miss. They became more frequent and longer duration over time as I tried to (unsuccessfully) find the problem.

- I tried switching the coils but the problem didn't seem to move.

- I replaced plugs, but it remained.

- The ground fix had been done prior to me owning the bike, but I cleaned and regreased the connections at each coil and the battery.

- The start switch has seen some heat in the past, but has a relay wired in now so the main power is going around it.
- It had a fuel injection controller on it, so I disconnected it. When I wired things back up, the bike ran fine, so I thought the problem was solved.

Earlier this week, it missed twice on the way in to work but otherwise seemed fine. It was substantially worse when I left for home. About halfway home it was running on only one cylinder. When I got home I pulled all the grounds and checked them. After reconnecting them it ran great. I rode to work and back the next ran fine until about a 1/2 mile from my house on the way home when it missed once. I started it this morning and it was missing like before and within 100yds of leaving my garage it was back to one cylinder.

+ The key difference between this year and last is that I have no FI light this year, whereas before it would light up when it missed.

Any ideas what I should check?
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post #2 of 20 (permalink) Old 10-26-2019, 05:37 PM
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Check your oil level and smell. The Fuel Pressure Regulator or FPR, is a known fail item that fails due to age, not mileage. When these fail, too much fuel gets into the combustion chambers and the excess fuel washes down teh cylinder walls into the engine case. Change the FPR, change the oil and ride around the block, then change the oil again.

Here's a link on How To change the FPR;
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post #3 of 20 (permalink) Old 10-27-2019, 03:33 AM
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Open and clean the connectors under the seat and left side cover and check your wiring if you used vampire clips to connect your fuel controller.

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Last edited by fastspek; 10-27-2019 at 08:33 AM.
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post #4 of 20 (permalink) Old 10-28-2019, 10:22 AM
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Does the FI light come on the the fuel prime takes place???

Starter switch >> the heavy load is the headlight.

Did you check the Ground wire at the Brake Pressure control valve?

Check this>>

While there, do the part to pull error codes.

Previously when the FI came on, were there any speedometer issues??

Vampire clips score the wire strands which will break at some time. Check carefully.
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post #5 of 20 (permalink) Old 10-28-2019, 10:25 AM
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Not that this is your issue but my 05 1800F started acting poorly like it was missing about every 1/3 stroke. The end result was very poor power. I took it in to get it fixed and the battery tested bad even though it showed the correct voltage. I ended up replacing it and the problem was gone. Something to consider...

2005 - VTX 1800F - Silver
2008 - Shadow Aero 750
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post #6 of 20 (permalink) Old 10-29-2019, 07:09 PM Thread Starter
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Wouldn't a bad FPR be accompanied by a declining fuel mileage? The exhaust certainly smells like fuel...I'll check the oil.

The FI2000 that was installed by the PO did use the vampire clips. I already checked the ground connections, but I'll look for broken wires as well.

The battery is new last year and has been maintained on a tender when the bike is parked.

No speedometer issues with the previous instance. FI light comes on during the prime (when all the other lights come on as well) but shuts off immediately after priming is complete and does not flash any error code when idling. No FI light when it misses or when I'm limping along on one cylinder.

I mentioned the start switch only because it is a known point on my bike where a bad connection may exist.
The two pin plug under the left side cover is in good condition.

I am unaware of a "ground wire at the brake pressure control vale." Can you point me to where that is?
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post #7 of 20 (permalink) Old 10-29-2019, 07:56 PM
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Check the TPS connector next to the throttle body. Mine was cutting out on exceleration. I cleaned & put a little di-electric grease on it and it's been fine for the last two years.

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post #8 of 20 (permalink) Old 10-29-2019, 08:18 PM
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I had this problem in the past. Turns out the problem was the way my "power commander" was connected to the main wires using "vampire clips". Over time the vampire clips frays the ignition wires and causes the problem. I removed the vampire clips and connected the wires using connectors. I had to first splice in and short piece of wire to replace the frayed wire.
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post #9 of 20 (permalink) Old 10-29-2019, 08:35 PM Thread Starter
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Oil smells clean.

Throttle response seems fine to me...except for one cylinder not firing...and the problem occurs throughout throttle positions (idle, midrange, and high speeds). When the problem occurs, increasing or decreasing RPM has produced no change in behavior.

I'll try to check wiring tomorrow and see if I can pull any codes.
- Last year it didn't give me any, not really expecting any now, but I'll be in the area when inspecting the wires.
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post #10 of 20 (permalink) Old 10-29-2019, 08:50 PM
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Verify the injectors are functional.
12-13 ohms.
Better yet +12v and ground. I would pull ECM connector for test and listen for the injector click.

Black/White wire from the ESR (Engine Stop Relay) provides +12v to all FI devices when energized.

Wire colors on the ECM drawing.
Attached Images
File Type: jpg 02-03 ECM main wires.jpg (380.3 KB, 3 views)
File Type: png 1800 fuse-relay-mydiagram1.png (43.4 KB, 3 views)

2005 1300c Red, Mustang seat, HK 2.5 straights. Leds for safety-front & back. 194,184 VTX miles
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