6th Gen Surging - Possible bad fuel pressure regulator?

Over the past week or so, I've noticed some surging with my 6th gen. This kinda has me puzzled and I'm not sure where to start tracing this down at. About a week or so ago, my speed kept dropping on the way home. I didn't think much of it as I was tired and it had been fantastic all day. I went out again the next day and all was fine so I just blew it off. On the ride home, the same thing happened. I paid much more attention to it this time. My speed would slowly drop off, and I would have to roll back on the throttle to bring it back up. I would only have to twist the throttle a few degrees (3-5... nothing major)to bring the speed back up, but there was a very abrupt acceleration as if I had cracked the throttle a quarter turn or so and I would accelerate beyond my original speed. I haven't had a chance to get my dyno tune yet and have been running Cozey's map and the default DynoJet map till now. Just for sake of trying something, I loaded the zero map to see if it was tuning related.

A few days went by without anything happening and it came back again last night. Same thing as before, however, the throttle response was even more abrupt. I went out again today and all was fine till my ride home. Things were much worse as my speed was dropping even more and it was occurring more frequently. Tonight I also noticed that it seemed as if the engine was being starved of fuel as it felt like that was a miss as I was losing speed. As soon as I would twist the throttle open a small amount, it would speed back up and accelerate as normal.

The few things that I've noticed are that it only happens at night, and it seems to be from a lack of fuel. Other than this things are running fine. I had it up to 135mph today without missing a beat, temps are running 167F-178F depending on temperature, and all is well other than this surging.

Tonight when I got home I busted out the phone to see what I could come up with for you guys. I slightly cracked the throttle and locked it there with the Throttlemeister . This is what I came up with:

[video=youtube;3Rx95RH65wY]http://www.youtube.com/watch?v=3Rx95RH65wY[/video]

Not sure why, but everything I use to convert the video to something viewable other than on a mobile phone inverts the video... so it is upside down.

The video shows the surging that I experience on the road as I'm cruising along. It doesn't appear to be specific to a certain RPM range. It drops 500-700 RPM, sputters in the process, and then returns to normal. Rinse and repeat.

At this point, I'm thinking it is a lack of fuel for various reasons. I haven't had a chance to dig into this yet as I've been busy as hell lately. A few things come to mind such as a vacuum lock in the tank, bad fuel pressure regulator, bad TPS sensor, pinched fuel line, faulty power commander.

Any other suggestions on where to start? I'll probably start tracking this down tomorrow evening after I get out of class. Obviously the video being posted would be nice and I will make sure that it gets there tomorrow.

Thanks guys!

 

This is probably stupid and obvious but check your battery terminals. Had the recall done yet? Check that blue ground jct connector that sits behind the fairing about by your left knee for heat related damage. Check to make sure the intake manifold clamps are tight. I stuck several hours checking out a VTX 1800 with a not totally different symptom only to find out the problem was an air leak caused by a loose intake manifold clamp. I've come across the same thing on VTX's twice since then...now it's an easy fix. Those are the first things that 'pop' into my head.

 

I would start with unplugging the Power Commander and checking the fuel pressure.

 

Video has been added. Everything I use to convert it flips it upside down so just ignore that.

Toe, will give that a shot. Rode her to class this morning and everything was fine. No surging, nice and peppy. These intermittent issues are always a PITA to troubleshoot...

Dizzy, will be checking that as well. Thx.

 

try unpluging the TPS and make sure you have a good connection.

 

Dizzy - Yes, all recall campaigns have been completed on my VFR.

 

dumb question?

you installed the o2 eliminators with the power commander right?

 

yes. and de-paired, de-snorkeled, de-flappered, and de- evap canned with 1998 headers.

 

Hold the phone upside down next time. :crazy:

 

Thats what I would say because I was taught that you cannot diagnose any fuel injection system until you know the fuel pressure is correct.
Also I would like to ADD that I would just check for air leaks first by spraying around the intake boots and air intake plenum chamber.

90 % of the time it is an air leak.

BTW...you did not give us the milage on the bike.

 

Thanks for the smartass comment Cunda... the original file is right side up ... but it is actually a good idea LOL.

around 24k miles. haven't checked lately but i know I havent broken 25k and have broken 23k.

 

With that low amount of mileage i would rule out the fuel pressure regulator.
But you can check the pressure. Get a gage and get a workshop manual. MUST HAVE!!

 

Got vacuum gauge and the shop manual but just haven't checked it yet. Need to get my hands on a gauge to test fuel pressure from the pump. Hooked up the power commander tonight to check the TPS sensor. Throttle position stays constant while RPMs fluctuate so I think the TPS can be ruled out. I shorted the system check connector and it threw a MAP sensor code (2 blinks). I've unplugged the MAP sensor and plugged it back in. Power Commander is disconnected. Ground block is clean, no melted wires, and tight. Battery connections tight. Will check the fuel pressure regulator and insulator clamps tomorrow evening to confirm they are within specs. I think I know someone with a spare MAP sensor around here and I will see if they will pay it forward back to me lol.

If it is sucking air around one of the insulator clamps, I should be able to test it by spraying carb cleaner around the boots correct? If I remember correctly, this will stall the engine if it is sucking air...

 

I meant to ask but forgot... Will the de-paired, de-snorkeled, de-flappered, and de- evap canned mods trip the map sensor or no? Could also be an old code.... I plan on clearning it before taking it back out.

 

Not quite. The carb cleaner will get sucked into the air leak and cause the engine to speed up.
If you have a can of dye penetrant then it will leave red die all around the air leak.
Check and tighten all the clamps.

 

I had what sounds like the same problem with my 04 last year. I would be cruising along and the engine/bike would start slowing down, give it some throttle and it would lurch and take off again. It would happen over and over again, even if I went up or down a gear. I could flog it all day and not have a problem, it would just happen during steady cruise. I had a PC III and O2 elims, but otherwise stock. I never did figure out what was causing it. Over winter I swapped in an '06 ECU and harness, removed the PC III, and I haven't had the problem since. I'm still using all the same sensors, so it must have been a connection problem, or the PC III. I've seen a few other posts describing the same problem, but I've never seen a definitive solution.

I wouldn't rule anything out unless it's been tested or replaced. My CBR fuel pressure regulator failed at less than 5000 miles.

 

Sounds like a warranty problem. 5,000 miles!

 

im de-paired, de-snorkeled, de-flappered, and de- evap canned , with a motad and mine's running good, so no, it wont trip the map sensor.

 

Well, I've ridden the last 4 days without issues and nothing has been changed on the bike. I did clear the codes that were stored as well as unplug and plug in the MAP sensor. Still running the same map and such as well. Everything has been fine. As a matter of fact I went out for a ride with dad today and pulled a monster wheelie (and was trying not to). It scared the shit out of me because I've never pulled one that high. The hump in the ride had a lot to do with it.

I did some research on the issue and found a posting on a Kawi forum describing the exact same issue with throttle response and it was related to a bad power commander. The only difference was that his would intermittently lose communication with the computer when hooked up and mine does not. I've heard of many many reports of a faulty PCIII and would highly suspect it. The only other things I can think of is that there was a pinched fuel line under the tank and this remedied itself when I lifted the tank to mess with the MAP sensor or that the very very funky weather/humidity we were having wasn't going over well with the bike. I've seen that many times with carbureted systems but never fuel injection.

As of now, all I can do is rideon and enjoy until the problem comes back then start checking more. Hopefully it doesn't and I've got nothing to worry about.

 

I noticed my 02 doing this when I rode it home from Dallas (2000 miles in just three days). When I got home , I removed the PCIII and hooked up the O2 sensors and the bike seemed much better but the problem came back. I reinstalled the PCIII and elims last night and hooked up the laptop to see if I could sort the issue out with fuel. It had the usual map for a bike with a TBR exhaust but the numbers were really strange to me. Not knowing how the stock map looks it is difficult to say what the PC map is compensating for. I decided to tweak the duty cycle at 20 and 30% throttle openings between 2000 and 5000 rpm to richen the mixture, making the assumption that I was experiencing lean surging at cruise and or very small throttle openings.

I had the bike out for a few hours today and it didn't surge at all but it seemed to have more vibration in the bars. I guess you can't have everything eh! I will put a few more hours on it before I declare victory here and then I'm going to keep tweaking to see if I can get the best of both worlds.