The problem disappeared again for six weeks and returned with a vengeance. It worsened in the past two weeks, so bad that it started to affect idle. I was fairly certain it was a leak inside the tank causing reduced fuel pressure and that indeed was the problem. However, it was not the component I suspected, which I thought for sure would be the high-pressure corrugated plastic hose downstream of the fuel pump, which has been a problem for others. It in fact was a poor seal on the fuel-pressure regulator, and it was leaking from that point. I replaced most everything in the tank except the fuel pump, so now I hope I'll be trouble-free for a while, as related to this area anyway.

 

As an update, the repairs inside the tank didn't fix the problem, although there was indeed a leak at the regulator that needed attention. In the two weeks since that effort the problem had become steadily worse, and I was seeing weird TP values displayed on my PV gauge--e.g. 3-10% at idle and sometimes +10 what it should read elsewhere. It would intermittently buck, spit, and idle poorly--and I've had it parked in the garage for the last few days.

Today I installed a new TPS and for the first time in recent memory it ran flawlessly in three runs. No idle weirdness and no misfiring or popping, a real departure from the recent norm. Because of the strange TP values I was seeing I was certain, or at least as much as I could be under the circumstances, that the TPS was bad. Let's hope it stays this way, but I'm cautiously encouraged.

 

Could be the Fuel Pressure Regulator (FPR) ($29)

The FPR is a mechanical device located in the tank...when the fuel pressure starts to go too high...the FPR opens and re-routes fuel back into the tank...no codes...no warning...mine was sticking open occasionally...slow to close. The low fuel pressure could cause a misfire. You stated you fixed a leak by the FPR...did you replace the FPR?

Funny thing...this is a STOCK item at the dealerships...does this mean the FPR failure is common?

 

Yes, the FPR was replaced, as well as all the interior and exterior fuel hoses. My assessment is that the leak was causing the intermittent misfiring on the highway at low throttle inputs, the one that plagued me for a full year. That problem would come and then disappear for sometimes months at a time, making diagnosis impossible. The TPS was causing the more-serious problems encountered in the past couple of months, namely quirky idle and intermittent misfiring at mostly slow speeds.

I rode it again yesterday and noticed something else. Over the past year or more my TP value has been higher than expected, and I attributed it to the 255-cam upgrade two years ago. At highway speeds it would run around 10% @ 50-60mph in 5th or 6th gears when stock, but later after the cam upgrade I noticed it was higher, usually around 15% under the same conditions. Now it's back down to where it was originally, suggesting the TPS has been bad for a long time, and only recently started showing any overt misbehavior. In the latter stages, only last week, it was so bad I decided to park the bike, and TP values were very abnormal, often 10% at idle.

 

This is good news... that you may have found the real problem.

Post again if this pops up again, OK?

 

That makes sense, as the tp wouldn't throw a code as the ECM is just seeing it operate. Good luck looks like the problem is solved.

 

It did throw a TPS code repeatedly the last few weeks. It was P0122 (TPS open/low EFI), which I think meant that it was creating an open-circuit intermittently, and the ECM wasn't reacting well to it.

 

FYI, I had a real problem with autolite plugs in my engine. Rear cylinder misfire & no fire codes galore. Switched back to HD stock plugs. No problems. Probably not your issue but wanted to throw that out there.

 

I have an 09 electra and I get a mis fire through the cruising range. 2750 to 3500 rpms it happens as if you were throwing a light switch on. Never thought about the Fuel Pressure Regulator or changing plug wires. The HD shop has had the bike for 4 weeks now and they can't figure it out.