Low rpm stumble

It's a bit hard to predict, but it seems to happen at no-to-slight throttle openings, and low rpm, maybe 2500 rpm or a bit less.

Probably I shouldn't let it go that low. Anyway, the bike will give a harsh stumble, and once it even stalled. I automatically hit the throttle to avoid the stall/stumble, and then you've got a wild bucking bronco ride. And feel like a dork.

I've had my 1998 for about 2 months, and put maybe 1500 miles on it. It currently has 29,000 miles on it, and looks to be well cared for. It has an Erion slip-on pipe, and a PCII. I don't know anything about mapping.

Does it need some sort of tune-up? Whadda ya think?
Thanks,
Eric

 

Does it hesitate to start on first try? It sounds like it needs a new fuel filter or even a fuel pump.

 

Now that you mention it, yes - I have to give the throttle a little blip when I hit the starter button.
Thanks. How'd you know?

I guess I'd better go find that fuel filter.

 

These bikes dont like anything below 4k. I dont really go below 4500 rpm if I can help it. You're lugging the engine.

 

Do a throttle body sync too, it might help a little with low rpm problems.

 

Others here have experienced the same problem and it got fixed with a fuel filter replacement. What you can do is download the service manual at http://vfrworld.com/forums/specifications/3161-downloadable-parts-catalogs-service-manuals.html

If you go to the Fuel Injection section there's a troubleshooting guide that'll walk you through.

 

I just joined the thread and got my answer about replacing the fuel filter by the second thread! And I just downloaded the service manual...thanks everyone.

 

change fuel filter, adjust idle to 1300 rpms and give it a test. throttle body sync after that if it isn't fixed. all are super easy to do. the only thing hard about doing the throttle body sync is getting the manometer.

 

It's not the easiest job in the world, but doing it yourself will save you 4 -- 5 hours of labor depending on how crooked you dealer's service department is.

http://vfrworld.com/forums/mechanics-garage/23649-5th-gen-spark-plugs-fuel-filter.html

KC-10 FE out...
lane: :usa2:

 

I just used vacuum guages, you will need 4 unless you want to do meter swapping, on VFR discussions a guy by the name of wizzard did a "whats missing from the book" essay for the 6th gen as the starter valves ( the parts you adjust to sync the TB's) is missing the procedures and exact settings. basicaly its this: the book says +/-20mmHg from the base TB(#4) is fine. in reality(this i know first hand) this is off. the conclusion is thus, set them to the 5th gen settings just flip the order to meet the vtec engine. so the 5th gen base is #1, and its as on mine goes thus #4 is base, #3 is -10mmHg #2 is +10mmHg and #1 is 5mmHg away from base. this is only a suggestion and should not be taken as gossple. I found it evened out my bottom end and made my 0-20% throttle opening smoother. there is other things that you could do to do essentialy the same thing. But then again i dont have a PC2/3 on my bike, so stock adjustments was where i fixed the issue, BTW you will need to get your stealership to reset your ECU as it will want to run in limp mode after the adjustments are done(the map will read no vacuum and AIT gets unplugged)

 

The only problem with swapping it around and using a single gauge is that it is a royal pain in the ass. One change to one cylinder can make a change to another after you've got it set and it gets quite hot between the cylinders really quick.

I will say that I did have the occasional stumble here and there with the idle set at 1200 RPM like the manual specifies. It would even randomly die from time to time while shifting gears. I bumped the idle up to around 1300-1350 RPM and that cured most of it.

Now that I have removed the PAIR system, O2 sensors, and synced the starter valves, the bike runs super duper smooth. A little bit of normal maintenance should take care of all your problems and you should be ready to start doing what you want to it instead of taking care of problems.

KC-10 has a good point on the spark plugs. Unless you've got records of when they were last changed it sure wouldn't hurt one little bit to put some fresh ones in.