Can anyone contribute any info or suggestions... On Irene, my 1999 VFR (128,000km)... At cruising speed (approx 4000-4500rpm) the engine hesitates when I crack the throttle, then clears up after a few moments or if I open the throttle further. There doesn't seem to be any obvious environmental condition. It has occurred whether it was cold or warm. What I find confusing is that it doesn't happen all the time. It'll do it a few times, then it won't do it. But it has been doing it more often than before. Also, if I give it full throttle, I get a visible plume of black smoke, as if it was running rich. The spark plugs have good colour. Gas mileage is pretty well the same as before. And the engine does not burn any oil. If I crack the throttle starting from a different RPM, i.e. 5000rpm or at 3500rpm, it doesn't happen. Based on the factory manual trouble shooting guide, it does seem to point to the TPS. The TPS is a electromechanical. It sends a voltage to the CPU that increases as the throttle is opened. So if the contact is worn or dirty at that point, it could send the wrong voltage and cause the wrong mixture. But why doesn't it do it every time??? So I'll first check the connector (and every other connector - MAP, pick up coils, etc.) for corrosion or looseness. Then I'll perform the voltage/resistance test on the connector and TPS terminals as per the manual. Lastly, I'll swap the TPS from my 2000 Red bike. I now see that the mounting slots permit some adjustment, so I'll carefully mark the position. If it solves the problem, I'll have to try to hunt down a replacement TPS. I've started googling for TPS, turns out that there are hundreds of different models. I did find a model that starts with JT3R, but not the same 81022 suffix. Also, the picture provided doesn't help determining if it has the same dimensions or mounting holes. tps sensor motorcycle parts FD0104 motorcycle parts China products ACURA INTEGRA HONDA CIVIC PRELUDE ACCORD CRX TPS SENSOR : eBay Motors (item 280487548613 end time Apr-12-10 09:56:35 PDT) This second site has a unit for Accuras and Honda CRX #JT3R 606559. It looks a lot like the VFR unit. I don't know if the connector would be the same. It seems all these units specify the same voltage (5.0v input, 0-4.5 volts for closed to full throttle). It would make some sense that Honda would use similar pieces. What do you think? Frederic
VFR TPS Glitch update I had posted a couple of months ago that Irene had developed a transient stumble around 4000rpm. I checked all sensor readings, all in spec. I proceeded to change the gas filter and purged the injectors, with only partial results. Aggravating! In the interim, my battery failed and so did my R/R. Because I usually leave the Tender on, I hadn't noticed any symptoms till one day, she just quit completely, miles from nowhere, of course. So new battery and new Electrex R/R. I now have a charging system. Oddly, the transient stumble has since vanished!!! Could it have been due to marginal system voltage?
The the "stumble" is a known problem on the 5th gens. Pretty much everyone experiences it. Mostly its around 5k rpms. I hardly ever go below 5k since anyhing lower is low rpms for this engine. From what Ive read is the stumble is the ecm leaning out.
Voltage critical? Actually, the bike had never had a stumble, and since I replaced the battery & R/R, the stumble has disappeared. I can cruise all day or transition through that RPM zone smooth as butter. In retrospect, it seems I've had a weak R/R for some time, hidden by the fact that the bike was constantly on the Tender. Turns out the battery died (it was a stock Yuasa only 2 years old) partly due to the failed R/R. Also, I'm told by my resident expert that leaving batteries on the Tender for long periods of time without periodically cycling the battery (i.e. running the bike) will shorten its life. So the FI appears very sensitive to voltage levels. Unless the battery is in really good shape, things start acting up. Thanks! frederic
