I wanted to post this while it is still fresh in my head.

I went to pick up my son this morning on my bike and when I started it up I knew that something was wrong. The idle was about 200-300 RPMs high, it stumbled off of idle, it would even miss while accelerating. Everything was really running fine before...what in the world could be wrong. Well, I dumped the bike back at home took the Blazer to get my boy and started working on it when I got home.

Many of you have this figured out already, no doubt. However, for the rest of you that, like me, are clueless...

I went through all kinds of scenerios, do the PC III's have a virus? Is that why so many people are having stumble problems? I tried to upgrade the firmware...I was doing this while the bike was idling...it immediately stalled. Then the PC III and Laptop wouldn't communicate...AHHHHHH! I disconnected and powered everything down. Re-connected the laptop and attempted to start the bike...nada. Turned the bike off and hooked up the 9 volt battery...re-loaded the map that was in the bike, disconnected the 9 volt and whammo...the bike started. But I noticed that again it was idling about 200-300 RPMs high and the throttle position was searching. I reset the throttle position and took a ride. All was well for about 5 miles then it started missing and coughing and stumbling...back home. Connect the laptop, and immediately saw that the throttle position was off again...what the heck? While checking the USB connection I saw the throttole position jumping wildly. HMMM...

A little background. I originally had a Terminal Velocity II on this bike and had to re-connect the TPS wires when I removed it. I used a protected quick-type connector but for what ever reason it was not making good contact. I took it all apart and soldered the dang thing. Re-loaded the map and reset the throttle position. Took her for a ride and my old bike was back.

Sorry this is so long, but I wanted to get this out there since so many are having problems with stumble. I know that you all did not have the TVII on your bikes so you won't have the problems I did, but could this be related? Could the problems DynoJet is having with stumble be due to bad readings from the TPS to the PC III? Or could the PC III be loosing the throttle position settings?

Everything is fine now for me, but after this experience I sure feel for you guys having this as an ongoing problem.

 

Good point, on any TPS based system, such as the PCIII, correct throttle position is everything. I am running an S&S ECM that is largely a TPS system also and find that I have toperiodically adjust my mechanicalthrottle plate adjustment, it seems todrift over time, I can tell by how the bike runs. If this is happening to a PCIII you could be messing up your entiretune by re-zeroing the TPS adjustment instead of adjusting the throttle plate if the plate drifted out of adjustment. This is because, when the engine was originally tuned and the TPS zeroed, the mechanical throttle plate position and the TPS sensor's voltagesignalwere directlyin sync with one another. But, if you just re-zero your TPS if insteadyour throttleplate is out of ajustment, the two could nowbe out of sync and your entire tune will be off. On my bike I simply adjust the throttle plate while monitoring the ECM's TPS signal to get it zeroed once and awhile to solvevarious tuning problems, however for you"by the book" guys, there are more sophisticated, but timely adjustment routines.