Help: I remain fixed position on throttle but RPM"s go down!

I have a 2003 VFR800. If I goto say 5k RPM's and hold throttle, my RPM's start to go down slowly, until the bike is surging like crazy (once the RPM's get real low). I have tested this over an over again. What could be causing this?

I noticed it a few days after installing a PCV. Not sure if its related. I installed the O2 eliminators, and I am running the Two Brothers map (I have a Two Brothers exhaust and K&N filter). I have tried other maps too, but same effect.

Could this be a problem with the O2 eliminators? Could I have maybe pinched a hose or something when putting in the PCV? I just need some direction to help troubleshoot. Any ideas?

 

Remove the PC and see if it still happens.....sounds like it could be the 02 eliminators though. I think someone here said they had some bad ones....

 

If they were "bad O2 eliminators", its just a connector and a resistor right? So what would I do in that situation, just buy a resistor and replace the resistor? I can pull those and check the resistance across it, also I just snapped those things in. I didn't electrical tape them or anything like that (it didn't say I had to in the instructions). Maybe one of them didn't click in all the way, but I would have thought I would see some sort of fault code or something if an O2 wasn't present.

 

You can get them at radio shack for couple dollars.

Make Your Own O2 Sensor Eliminators - Modifications - VFR Discussion

Try to un do the PC V and bring the bike back to original condition to see if the problem go away. If it is than the map might be the issue.

 

I get the same problem from time to time. Just twist the throttle a tiny bit and it wll go away for a few minutes. I've never been able to figure it out since I put on my PC3.

 

I had one of the resistors burn out on me. CEL came on and it seemed to run the same. I replaced it and the light went out. Didn't really seem to make much difference.

 

Thats a total PITA, I am not willing to live with this. In closed loop mode it needs to be able to do its thing, something has to be wrong.

 

Small wonder it's fubar--It can't run closed loop without the O2 sensor.

Who's the brainiac that came up with that idea--that resistors could replace a device that generates voltage proportional to the amount of oxygen in the exhaust gases...? Sounds like voodoo electronics

 

well in theory, if the O2 sensors report back "all is cool, don't do anything" back to the ECU........then that's what it should do.

SUCKS! i have spent today googling this, and its thread after thread after thread, of people who put PC3 or PCV in that have issues when it goes into closed loop. The ONLY thing I can think of is, buy autotune. That gives you a wideband O2, which will report back actual correction that should be made and allow the PCV to make those.

Thoughts? Should everything work fine with PCV and O2 eliminators?

Its possible that this has nothing to do with O2 eliminators and PCV and is just an issue being made more apparent right now, such as an air leak, or something. The thing is, I would think that with an air leak, pinched fuel line, etc you would see an issue on accel/deaccel as well as closed loop.

Looks like Dynojet will be getting an additional $250 from me for the O2 sensor (autotune). I hope that shit is rock solid and awesomeness.........i can't take this RPM dropoff BS.

 

When you say "I can't run closed loop without the O2 sensor" you mean the stock O2 sensor or the autotune?

 

Simple squidbilly closed loop mixture control: the O2 sensor generates a voltage proportional to the differential partial pressure of oxygen in the exhaust gas versus the outside air. The ECU reads this voltage and uses it to adjust the injector timing with the goal of stoich mixture. If the voltage is missing or out of the expected range then the ECU substitutes a "limp-home" value (usually rich) just to keep the motor running. It won't run good but it will get you home.

It seems like the last time i read the 96 pages of troubleshooting in the manual that the ECU would throw a trouble code if the O2 was not working properly?

That surging you have is the motor running rich--it is being flooded with fuel. To verify this just pull your spark plugs and tell us how they look...i'll bet they won't be dry and gray or white.

i'm fairly certain a stock sensor would work properly with the stock ECU since Honda usually makes good stuff that works, but all bets are off for modified systems.

There was a company that showed a basic lack of understanding of carburetors. They sell carb kits that make the bikes run really rich and advise you to drill out the orifice in the vacuum slides (that's for the old bikes). i don't know the autotune device, but it may be the same sort of transfer device as the carb kits--transfer money out of your pocket to theirs.

 

If you're using closed loop mode, plug the O2sensors back in, and block off the PAIR valves. If you don't want to use closed loop mode, find the setting in the Power Commander that turns it off, and turn it off. Using closed loop mode without an O2 sensor is like trying to walk with no legs!

On the other hand, perhaps the PC is sending the wrong signal to the ECU. Make sure it has a good power and earth with no voltage drop: if it's reading 0.1V too high or too low, the ECU will try to adjust the fuel to bring what it thinks is the O2 sensor back to the correct voltage, but it will never get there, so you'll either get lean-out, or it will become too rich, and quench the combustion until it stalls.

 

What setting are you referring to? My understanding is that for the power commander to influence closed loop mode you need an autotune module. Are you saying there is some checkbox or something like that I can just uncheck?

 

Believe me, I don't want to live with it either. Perhaps I need to pull my resistors out and check to see if one of them is burned out. It happens so rarely to me that I simply gave up tracking it down.

 

Dyno is your answer or Auto tune to adjust with your riding behavior, just saying....

 

It just seems like if corrections are being made, while the bike is in closed loop, then there must be an issue. I checked the resistance of my O2 eliminators today, and they are fine, one was at 327.2 the other at 328.1 so well within typical resistor tolerances.

Dynojet tech support recommended I re-calibrate the TPS (I never did that before as its supposed to not be necessary as it comes pre-calibrated). So I did this.

Also, in thinking that the way the corrections are made (leaning or richening) is basically via electrical, I checked my battery terminals. The ground terminal was not what I would call loose, however I could certainly tighten it a bit, so I did. After this I took it for a test drive, and it seemed fine. I did warm the bike up. It started to rain, so I couldn't test it for long, but I am pretty sure the O2 eliminators are fine now. I could have a bad PCV, or I am thinking the electrical system is at fault. If I continue to have the issue I am going to start troubleshooting for common electrical system issues that are well known to our bikes. Because if the current is off, then thats the same as the resistance being off, its going to result in a differential of power being signaled to the ECU is my thinking, resulting in changing the mix. Everything I read leads me to believe that if your in closed loop, and you have eliminated O2 sensors properly, then there should be no corrections being sent back to the ECU, so RPM's should be able to be held constant.

If the problem does indeed go away now, I am not sure if its the tightening of the terminal or that I re-calibrated the Throttle Position in the PCV. I really don't want to just throw an autotune at it, because that could mask any real problem that may exist.

 

Looking for some direction from you all on my problem, here is an update:

My O2 eliminators are good. Tested 330ohms, solid clean connections.
I found my main fuse holder slightly melted, replaced harness AND added the VFRness, did "The Drill", Stator, RR, Battery (load tested by autozone), and loom all look good.
I have ran a few helpings of sea foam, and also have not been babying the bike, I get on the throttle

Symptoms:
Bike looses RPM's even though the throttle is kept constant. This causes a surging motion, and the RPM's just keep slowly dropping.
Only seems noticeable while throttle is constant
I do get a bit of popping and spitting especially on deceleration

What are my likely culprits?

I have checked all electrical connections and grounds
I plan to take off the airbox tomorrow and start looking for disconnected vacuum lines (could this cause it?)
I also plan to check the insulators to make sure they are nice and tight (could this cause it?)

Its going to the dealer in about a week once I get all my parts in for a valve inspection, starter valve synchronization, oil change, plugs, fuel filter, and I am having them change the thermostat while they are in there.

In the meantime, I am hoping to improve my troubleshooting skills and learn more, so I have been reading the service manual, doing all this electrical troubleshooting to insure electrics are good, but want to move to the next most logical area, and I am not sure what to focus on. Vacuum lines and insulators seem to be straight forward, but maybe thats not the best place to focus on next?

I appreciate any direction. I don't have that much mechanic experience. I learned alot while just doing the electrical/charging system troubleshooting, fixed some things, but my main problem persists and I would love to figure it out before it goes to service next week.

 

I know this is back tracking but have you disconected the PC and see what she does. It sounds like you are chasing down anything you can to avoid the PC being the culpret.

 

friedleyjr,

Just got done removing the PCV. I unplugged it but left the O2 eliminators in (My old O2 sensors are no longer usable, I cut the wires on them).

Issue is still there, actually I didn't notice too much difference at steady thready with PCV vs non-PCV. I'll goto say 5000 RPM's and almost every 5 seconds or so I start to lose 100-200pm. Any ideas here? I am next going to take the airbox off and start looking for pinched hoses, removed hoses, loose hoses. and try to tighten the insulators

 

Here is some more update:

I took off the airbox and cleaned all electrical connections with electronics cleaner, and I use MAF cleaner on the MAP sensor.
I checked all vacuum hoses, no issues there
I tightened the insulators, a few were pretty damn loose
Bike still drops RPM's! I had it running at 9000 RPM's within 10 seconds I was at close to 7000!

It seems to idle ok, pulls hard, gives some spitting on decelleration.

I was going to sync the starter valves, but I don't have the gauges. Autozone and other parts stores here don't seem to have them either for sale or rent. Any ideas? i can get a set off amazon for like $75 if I want, and then buy a meter that can do tachometer..........I don't want to do the starter valves unless that is a likely culprit, and so I appeal to you all that know what would cause RPM drop like that to guide me.

Also while the bike was hot, I did another "The Drill" test, and checked the stator at both idle and 5000RPM's, rock solid. I have no electrical gremlins, doesn't shut off, no dashboard issues, lights work great without dimmin, ODO works great........

What can this be?

Brian