Engine in "safe mode"

Discussion in '6th Generation 2002-2013' started by SweViffer, May 13, 2018.

  1. SweViffer

    SweViffer New Member

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    My VFR starts to sound like it misfires when getting (really) hot. It's a lot of blubbering and exhaust pops, and frankly it's not fun in the long run. I've done some research (a LOT of forum reading was involved), and done some things to try to rectify the behaviour.

    My bike as it stands now have Two Brother exhaust without decibel killer. The airbox flapper is used as standard, but no PAIR.

    What I've done is:
    * changed fuel pressure regulator.
    * changed spark plugs.
    * removed PAIR completly (the solenoid was broken (always open) and the reed valves were stuck open, so that was no good).
    * cleaned the fuel injectors.
    * checked valve clearance (thanks Honda for the expensive service cost).
    * checked the IAT, and it produces the correct value cold.
    * the ECT is ok, I have no VTEC kick below 65 degrees centigrade and I do above.
    * the MAP seems to produce at spec.
    * bought a Rapid Bike Evo, did not help.

    My guess at the time after doing all this was that it may be either the O2 sensors or an ignition coil gone bad. Then I remembered reading something or other about a "safe mode" that you could start the engine in. I tried that, and everything was excellent. What I do is turn the ignition on, let the fuel pump prime. Then I turn the ignition off and after that press the starter button and then ignition on again. It works like a charm, and I finally (FINALLY!!) have a VFR going like a VFR should (some may argue about VTEC, I don't).

    Long story, but my question is if anyone knows what I by-pass by using this "safe mode"? Basically I wonder what the hell is wrong with my bike that makes the "safe mode" work? My guess is that my ignition coils are ok, otherwise I should have misfires even now. I think I know that the O2 sensors isn't used now, but are there other sensors also not used in this "safe mode"? Is the IAT and MAP sensors used to correct the engine map for example?

    Next on my list of tests is to eliminate the O2 sensors with resistors, and try "ordinary mode" again to see if that solves it. Other than that I'm a bit confused about other things to test, anyone have any good suggestions?
     
  2. SweViffer

    SweViffer New Member

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    Right, forgot to add that I've also cleaned all connectors I found and was able to disconnect. I have not cleaned the ECU connector, since I couldn't figure out how to disconnect that without breaking something, I've also not cleaned the earth hub (or what you should call it), the block in the front harness that was orange on the 5th gen. Other than those two every connector have been disconnected, cleaned and reinstalled (including all earth points I could find on the frame (2)). Have also checked the charging voltage, and it produces at spec (with all the original equipment, on a 2002!!).
     
  3. OZ VFR

    OZ VFR Member

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    My bet would be a faulty O2 sensor.
    Very easy and cheap to test.
     
  4. SweViffer

    SweViffer New Member

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    Is there a better way to check them than using sensor eliminators?

    Hmm, when I think about it I seem to recall a way to test the sensors in the service manual. Yes, in section 5-39 there is a way, by snapping the throttle open and closed. I'll run out and test it immediately.

    *runs out with computer to check*
    Luckily the bike was warm, so that was a rapid measurement.

    Reading the O2 sensor voltages measured by my Rapid Bike Evo I saw that the quickly closed throttle voltages didn't drop below 0.4 volt. The voltages seems stuck above o.6 V almost the whole time, just a small drop below (but not below 0.5-0.55 V) when closing the throttle. Seems broken.

    I'll try with eliminators as well just to see if that also produces a fully working bike.

    And on second thought maybe I should also disable auto-tune in the Rapid Bike. :)

    A question, is it possible that the bikes previous running with unintentional exhaust gas recirculation has broken the sensors, or is it perhaps oil and dirt from the outside clogging the air hole? Can you clean the outside of a O2 sensor without breaking it with something, maybe brake cleaner?

    Clarification: what I mean with the outside of the O2 sensor is where the cables (and air hole) are located. I've no intention of removing the sensor and try to clean the part stuck in the exhaust.
     
  5. OZ VFR

    OZ VFR Member

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    O2 sensors don't work properly until hot.
    I'd say it is just no good, I don't think cleaning it will help.
    You can just get a 220ohm resistor from memory and install it in the plug to bypass O2 sensor.
    I would definetly disable the auto tune.
     
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