Throttle stumbles like out of gas

Tried to go for a ride today but the bike was having issues. Basically when I turn the throttle the bike chokes and stumbles like its out of gas. Nearly bucked me off the bike a few times so I came back home to look it over. I have a PC3 so that was my first thought. I reset the map and tried again. Same thing happened. I disconnected my PC3 just to rule that out and the problem continued. No change at all. When searching the internet I have seen everything from new spark plugs to a TPS unit being replaced, which by the way is really expensive. Has anyone experienced a similar issue? I am riding a 2007 VFR.

 

I can't really help as I have never encountered anything like that.

In your shoes I would be trying to narrow down the possible causes. You have checked you are not out of fuel? It may indeed be something electrical like a throttle position sensor going south, but similar symptoms can be caused by other things like a batch of bad fuel, a clogged fuel filter, pinched fuel line, fuel pump issues etc.

So to avoid wasting effort on the wrong thing, it is time to put your thinking cap on and in particular analyse the events prior to and when this happened first. Has the bike had any work done? Did you refuel? How long since it was given a full service? Has the bike been in an accident, or dropped? Has it recently been out in heavy rain or driven through a flood? Are there any fuses blown? Is the charging system OK - Are the standing, idle and 5k rpm battery volts OK? Are there any other symptoms?

If the bike was running perfectly fine until this first happened, then you need to identify what changed? If the bike has a history of rough running then maybe it's just telling you it needs a service. Does the bike show any MIL codes? It is unlikely to be the PC3 but things like aftermarket alarms and immobilisers can cause all manner of weird behaviour.

Hopefully the above questions will at least allow you to home in on what is wrong with the bike. Let us know how you get on.



SkiMad

 

Those are all very good observations and comments. In retrospect I should have provided more information in my initial post.

My bike is garage kept and prior to this happening, noting had been going on with my bike. It had been about 1 week since I last rode and I have it connected to a trickle charger when I am not riding. I had about 1/4 tank of gas left and it was 1 week ago since last fill-up. The bike has never been dropped or in any accident. My bike always runs smooth and I have not ever encountered throttle issues, idling issues or the like. Maintenance history on the bike since I have owned it has included regular oil changes and 1 set of new tires. The only mod to-date is the PC3. I will have to check about the MIL codes and how to get those to show up on the dash. I will post the result if any are found. Fuses appear to be good. I guess it could be bad fuel, clogged fuel line or filter...etc. Still investigating. Thanks again for the troubleshooting ideas.

 

No MIL codes are showing up on the display. I know there is a service connector somewhere that I can use a jumper on to show any codes in history, but not sure were that is on bike. I have been searching internet....

 

Check air box. Maybe some THING moved in. Mil light connector thing is on right side by fuse panel. I think it's a green connector. It'l be the connector that's not pluged into anything. Search you tube for 'vfr800 mil check.' Good luck!

 

So here is the latest. Replaced all 4 spark plugs this morning and the throttle is some better but not fixed. It is much more subtle. I feel like I have masked the problem with the new spark plugs and not truly fixed the issue. Any other troubleshooting ideas? My last resort is to take it in to the local Honda dealer but........

 

Have you tested the fuel pump? Also is it possible you got some bad fuel? How did the old plugs look btw??




Rollin

 

The plugs were worn, black and looked terrible. Definitely needed to be replaced. Not sure how to test fuel pump but I will read up on that and see where it leads. I also syphoned gas out and replaced with enough new gas to show one bar on the display. Didn't want to refill entire tank just yet. Thanks for all the help. I am definitely learning a lot about my bike through this.

 

Your plugs should not appear black, not even old plugs. When FI fails it's often a bad electrical connection, a vaccum line detached or a sensor outta whack, so replace the lot !! Since signs point to your bike running rich, one suspect would be a faulty thermostat causing the engine to run too cool.

Stick yer finger up it !! Tail end of the exhaust of course..... is your dirty finger black or tan or clear ??

 

Its black and very dirty in the tail pipe.

 

Wash your hands, kid !

Running too rich so read up on all possible causes in your service manual. Read any codes. You might need to dig out your multimeter and run some tests.

Besides thermostat, a bad coolant temp sensor might be your problem.

 

Last time i looked there were 97 pages in the troubleshooting section for the EFI, and a multimeter will be your best new friend in the toolbox--sad but true, the cresent wrench sits lonely at the bottom next to the 3lb sledgie torque wrench...

 

The entire fuel system section ( carbs & fuel pump) on the older carbed bikes stretches to the modest length of about 12 pages, covering it all. 97 pages represents real progress, right ??

 

Haha Reg you just ride and leave the cleaning and maintenance to us ound: