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Discussion Starter · #1 ·
Okay, my problem has continued to progress to the point where my bike became unable to ride today. It's a 2002 VTX 1800, with a set of Bubs straight pipes, KN filter in stock housing and a Power Commander. Bike has 11k on the odometer and is ridden to my office (six miles round trip along residential streets) at least four days a week.

The problem has been apparent for some time, and is best described as a slight misfire just off idle to about 1/4 throttle. If, while in neutral, I hold it steady at the upper end of the stumble it pops and coughs, as it does while riding it. Rolling on the gas past 1/4 throttle usually cleans it out. I did pull and clean the plugs last weekend and found right rear plug to be fouled while other three were within acceptable range of color. Tips on the Buns are always black and sooty.

Until today, riding it was tolerable, although not fun, as I would just crank the throttle and ride through it and put up with the surging at contstant speed. Today was different, however, as it was as though someone was shooting at me.

I've investigated some of the possibilities and have not yet undertaken the ground fix or the removal of the factory air recirculation system. I DO NOT HAVE AN ISSUE WITH IT POPPING ON DECELERATION, SO PLEASE, with all due respect, DON'T OFFER THAT UP AS AN ANSWER HERE.

I've built bikes and cars to all levels since the early 1970s, so I can do whatever is necessary to fix this. Problem is that I'm bewildered as to the rapid switch from a slight stumble to an all-out non-functioning situation. My gut feeling says that it is most likely a timing/ignition issue, or a fuel injection problem. But being computer controlled, how is this traceable. I don't get any "check engine light flashes," as I might expect with an ignition problem. Likewise, my other guess is that there's a fuel injector or regulator issue, but again, no tell-tale signs.

If anyone has experienced anything close to this issue, I would greatly appreciate any input or suggestions. Just because I'm an old "grease under the fingernail" dog, doesn't mean that I can't or don't want to learn any new tricks. Thanks.
 

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I've investigated some of the possibilities and have not yet undertaken the ground fix or the removal of the factory air recirculation system. I DO NOT HAVE AN ISSUE WITH IT POPPING ON DECELERATION, SO PLEASE, with all due respect, DON'T OFFER THAT UP AS AN ANSWER HERE.
There is no need to shout, everyone wants to help.
 

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No 1800 guru here but heresy .02. Check your fuel pressure regulator. 02-03 have them on the fuel rail and they are notorious for going bad and fouling plugs, start the bike let it run for a minute and shut it down, pull the vacuum line off of the FPR, if you have gas in the line, there's your culprit . Second I would check my air filter and make sure it didn't need cleaning/replacing and finally I'd check the exhaust bolts to make sure they're tight. Loose will cause backfiring. Good luck. Hope this helped!
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It's a 2002 VTX 1800, with a set of Bubs straight pipes, KN filter in stock housing and a Power Commander.
I would say the issue is with the Power Commander, with only a pipe change and a K&N in the stock air box it doesn't need the Commander. I'd take it off and run the stock settings and see how it does from there.
 

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Discussion Starter · #6 ·
Backfiring...

Thanks for the input, Doug, but the Power Commander has worked flawlessly for five years. This backfiring problem has just steadily gotten worse over the last month. Fuel regulator is on my list to check. Is there a replaceable fuel filter in the system?

Another issue I remember is that when I took the air cleaner out and started it up I could see that the backfiring was tracking back through the intake manifold. In a carburetor situation, this might lead me to believe that there is too much fuel running into the intake. But with EFI, I wouldn't think that would be the case.
 

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I would take the Power Commander out of the loop, and check your fuel pressure regulator. The filter in inside your fuel tank, connected inline with your fuel pump. Even though your Power Commander has seemed to work good previously, It would be nice to get it out of the loop if not too much of a hassle, just to eliminate it from the list of possibilities. Has it had a valve adjustment? Perhaps a tight valve that is not closing all of the way, and popping exhaust gasses into intake manifold? Probably not. Just throwing some ideas out there. Good Luck.
 

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Not exactly sure how the PCIII's are installed on the 02 models but I do know it's different on my 06. That being said , the tap lines to the throttle position sensor have been known to go bad. But follow the install on the PCIII's wiring and just check to make sure nothing there is fouled up. Also, I know this sounds too easy to be true but check your battery terminals. The ECM will not perform properly if it's not getting a good connection from the battery. Use a socket not a screwdriver to tighten them down good. I can't recall how many times I've seen folks come on here with the same type problem as yours and most of the time the terminals just need tightening. Try the simplest things first.
And while you're there take a good look at the ECM and make sure that none of the wires are cracked or broken.
 

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Lots of good suggestions here. Make yourself a list and check things off 1 at a time. 1)check battery terminals. 2) on the first couple years 1800's had some grounding issues that were resolved on later models. One ground was eliminated. Check on bare-ass's vtx pages for instructions on early model ground fixes. 3) fuel pressure regulator. As said pull vacuum hose and see if there's fuel in hose- indicates ruptured vacuum diaphragm and replacement is needed. 4) check ignition to all 4 plugs. make sure you don't have a wire or coil issue. After that start looking at PC and ecm wiring, harness problems, or failed PC.
Good Luck.
 
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