Stuttering and power drop at low speeds

I've had my 2000 VFR800 for over a year now and its developed a stuttering problem at low speeds, and it seems to happen more when the engine is already hot.
Also it will sometimes drop RPMs from 4-5k almost immediately down to 0 but it always surges back before it gets that far.

I don't have any problems at any kind of speeds above 20mph. Spark plugs maybe, something cheap? Figure the plugs are due anyway, but I'd like to get every fixed in one go if at all possible since it's my only vehicle.

Voltages seem fine, 12.7ish off, 13 idle, and 14.5 at 5k


ALSO, Ever since I got the bike my tachometer at idle fluctuates a little like 100-200rpms or so, my old Ninja 500 used to do that so I figured it was normal but it messes with my OCD :\

 

First off - Hi and welcome to the MadHouse:welcome:

When you get a chance, please update your profile to include the specs of your VFR and a rough location - nearest city & state is fine. That way if there are other members nearby, you may find they are will be ready to swing by and offer help in exchange for some beer tokens.

Secondly, the folks on here would really like to see photos of your VFR (click the icon two to the right of the envelope and follow the prompts), and it won't be long before some start ragging on you until you do!

As for the problems - your voltage numbers sound OK, but you should be aware that RR failures were not the only issue with the early 800's - under-gauge wiring, poor connectors and poor grounds have all caused problems, and such defects can easily give rise to fluctuating and intermittent sensor inputs. These can confuse/upset the ECU and obviously result in very uneven running, as the ECU struggles to respond to weird sensor inputs. Another pertinent fault to be aware of is that stator can be working fine when cold, but the winding insulation can break down when hot and start to drain power - eventually leaving you stranded. So you need to do those voltage checks twice - once when the bike is cold and again after its good and hot from a 30 minute plus run.

Have a look at this thread

http://vfrworld.com/forums/5th-gene...how-fix-common-regulator-stator-failures.html

Note in particular the loom and connectors which need to be checked, as I suspect that this may be where the problem lies.

If the loom/connector checks draw a blank, proceed to the stator and RR checks. NB the stator check is done with the RR disconnected and you need to do them twice once with the bike cold and again when hot. You need similar volts AC on all three pairings of the yellow wires, - just take care with the test probes - do not allow them to short the yellow wires.

Let us know how you get on.



SkiMad

 

This sort of surging at idle makes me think it is related to the throttle position sensor TPS. If it also happens at partially open throttle at higher speeds then i would think it is related to an engine or air temperature sensor signal.

If you can download the manual there is a 96 page troubleshooting section just for the ECU and sensors, etc.

 

Disconnected the PCII and the troubles are gone.
I doubt its a problem with the PCII since its been on the bike ever since I got it with no problems. What underlying cause would do it?

 

Duo any luck getting this sorted out yet?

 

:welcome: to the madness
Have you try to reload the map? I have same issue in the past I reloaded the map and the problem go away.

 

Yes, and in fact the problem is even with the PVC disconnected.

Honda called today. They did not see the problem. I picked up my bike, it immediately did it, just like it always does, I brought it back, and showed them. They held the throttle steady many many times, and it would drop 1-2k RPM's at about 100 rpm's per second. They said its probably fuel pump or FPR and they took the bike back and will be doing a fuel pressure test and diagnosing. I really hope its the FPR and not the fuel pump. Doesn't look like you can buy the fuel pump separate, it comes with the filter, gasket, etc and its not cheap. I just hope they positively diagnose and fix, and I am done with this craziness, been driving me nuts. The bike sucks to ride when its doing this, no fun at all.

 

Signal, good luck getting the issue fix, keep us posted. Hated when the bike is :wacko:

 

At this point I'm just gonna keep the PCII disconnected, the ride is a hell of a lot smoother at take off. Its an old PCII with no USB so I'd have to get an adapter to even plug in.

I do still have fluctuation issues, they're just not nearly as noticeable.