6th Gen VTEC cutting in and out at VTEC transition...HELP please!

Discussion in 'Mechanics Garage' started by lonnieleyden, Aug 3, 2018.

  1. lonnieleyden

    lonnieleyden New Member

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    2008 VFR800 engine cuts out at VTEC transition. Worse at colder temperature. Hight temp engine cuts are less violent. Less throttle less violent ....WOT can cause major engine cuts on off on off on off. Tach bounceing aroung up amd down. shift and go past the transition and vtec is engaged and moter is holding steady at standing trottle but will cut out at agressive throttle. Been a 2 year ordeal for me. 3 shops. No Joy. Valve clearance done, vtec spool 12v test checks out. Fuel filter new plugs, new oil several times, replaced cam position sensor, ignition pulse generator, all 4 coils, ECU, throttle bodies, valve timing re-checked, ignition timing checked, cleaned and checked connectors and battery tems and frame ground. Stator and RR, IAT sensor, checked per manual. Bike is stock, 90k miles Mods, pair, O2 elim Any ideas? Link to a quick video. Here-----> [​IMG]

    Sent from my SM-G950U using Tapatalk
     
  2. 34468 Randy

    34468 Randy Secret Insider

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    That is an odd one. I haven't a clue. When you had it into the shop, did the techs check with Honda for suggestions?
    I assume at least one of the three shops was an authorized Honda dealership.
     
  3. lonnieleyden

    lonnieleyden New Member

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    Hi Randy Thanks for responding.
    All 3 shops were honda certified Honda dealers and the first shop only did an oil change and then told me to come pick it up and that it was probably the valves and would cost $1k usd. I said I'll do it and after that, they weren't interested in having it back. I get it but im not paying anyone a thousand dollars to do something i can do myself. So i ordered some feelers and pucks to engage the vtec valves and did the valve clearance.(60k miles) Most of the VTEC valves were out of spec on the tight side so ordered new buckets for the VTEC valves and a couple shims for the non vtec valves and made the adjustmet, set the valve timing and fired it up only to find that the issue was even worse. Meaning more violent VTEC transition as well as the main issue of the engine cutting in and out. So now off to shop 2 ...these guys had my Bike FOR 5 MONTHS!. The first 2 months they were nice and aggressivly troubleshooting and working with Honda techs and a very long story made short, they replaced the wire harness amd tried 2 differt ECUs only to have me come pick up the bike after 5 months. BTW when i came to pick up my beautiful baby, she looked as if she had been left outside the entite time. I was so pissed. (Thanks Escondido Cycle Center) okay so i did some reaserch and found Shop 3. Honda of Redlands. Thease guys were great. Assured me that they had the Techs that could figure it out. So i drop the bike off once again. They worked with tue previous shop to kind of collaborate their efforts and the first thing they wanted to do was check my valve clearance work and i understands why so i agree. Valve clearace checked out okay! I said told you so hahaha jk no but really. So turns out my tech actually rides a VFR as well so he's not letting this bike go until he figures it out. He tries everything and says it has to be the ECU. I remind him that the other shop tried to with no success. The tech says i dont care im ordering one. A week later i get a call that THE BIKE IS FIXED! ECU curred it. Yay! I rode the bike for about a month and it was great but then noticed a very slight hickup during vtec transition...Do slight that only i would be able to tell. Fast Forward 2 months and the issue as progressed back to were it was and thats where I am today. My god sorry for writing a book! Theres just so much relevant history. Ive just been dealing with the issue and staying out of VTEC (no fun) anyways, i commute 140 miles round trip per day to work and its a great bike. Just need to figure it out.
     
    Last edited: Aug 3, 2018
  4. skimad4x4

    skimad4x4 "Official" VFRWorld Greeter

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    Wow - that is a new one - and Welcome to the Madhouse.

    My gut feeling is that the ECU is not faulty but is behaving perfectly predictably in response to faulty sensor inputs which may in turn be due to damaged wiring providing intermittent contact. The chances of two faulty ECUs is pretty remote - so hopefully it is something more basic and cheap to fix!

    I am sure you or your mechanics have already examined the following schematic closely...

    http://www.lifford-cooke.com/motorbiking/documents/VFR VTEC PGM-FI Diagram 2002.pdf


    The sensor I would start with is the IAT (Inlet Air Temperature) sensor. If I recall correctly the VTEC mechanism is disabled until the IAT reports the bike has warmed up enough. If that sensor or the cabling is messing up, the ECU could think the bike is cold and prevent the VTEC from working - which sounds like the symptons you are experiencing.

    That schematic shows the basic VTEC system - and as you can see there is a whole heap of critical connections feeding inputs into the ECU - so if that connector was slightly loose it could very easily give rise to intermittent inputs which the ECU will still do its best to interpret and respond to.

    Indeed it may be that during the dismantling work undertaken during the most recent (partially successful) attempt to rectify the problem, when it came to putting things back they simply pushed a connector more firmly home, hence it worked OK for a while, only to work loose from vibration after a few weeks riding.

    If you look close that diagram shows all the expected input range values from the various sensors - so it should be possible for someone with suitable test kit to check the values being sent from the various sensors are within spec. If they all come up clear - then start looking for loose connectors or corrosion in connectors especially the IAT.

    Good luck - let us know how you get on.




    SkiMad
     
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  5. skimad4x4

    skimad4x4 "Official" VFRWorld Greeter

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    Aggh - getting trigger finger happy .. time for more beer.

    Obviously inputs from other sensors can cause the ECU to shutdown the motor entirely. So its not just the IAT which may need checking.

    For instance if the side stand switch input comes on with the bike in gear then the ECU will kill the engine. I am not sure from your description if the bike was just refusing to go into vtec or if the bike dies entirely. If so that can be caused by a defective wire from the side stand/kill switch circuit. Sadly just checking for circuit connectivity is not enough, especially for any cables located outside the frame as they are open to external forces and can be snagged. So you may need to flex "gently" any suspect wires and connections to see if there is a hidden break inside a wire causing an intermittent connection.

    I also forgot to ask were there or indeed are there still any MIL warnings on the ABS dashboard light?

    This video shows how to check for MIL codes and how to interpret them.





    SkiMad
     
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  6. lonnieleyden

    lonnieleyden New Member

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    Thanks for your reply Skimad! I actually had not seen the diagram that you linked above and its quite helpful and seemed to get me thinking about all the oppertunities to check items that i had not considered. So the wife released me back to the garage yestarday mostly because I must have had a blank look on my face while she was talking to me all Friday and Saturday..lol
    Yestarday i removed the throttlebodies and checked the spool valve and cleaned up the wireing for it, the ECT, Neutral switch, I eliminated the kickstand switch, replaced the camshaft position sensor, ignition pulse generator, 4 coils all with no luck
    So then pulled the top faring and checked the ECR FCR, fuse boxes, bank angle sensor, IAT in the airbox, cleared all the FI codes that i had induced from troubleshooting and no luck. Then istalled an ECU that i picked up from a salvaged 2009 VFR800 same part# but the bike ran horribly right away. Not sure what thats all about. I then put my ECU back and installed a new powercommander V that i had been itching to try and the engine is runnig smooth as butter until VTEC.

    Let me answer some of the questions you had asked above

    Fi warnings: unfortunatly the issue does not throw any warnings,

    Does the bike simply refuse to go into VTEC or does the engine die entirely.:
    It just struggles to go into VTEC. The engine seems to cut out and then comes back as soon as the RPMs return to the lower zone (when vtec is disengaged). As I mentioned above,the motor runs very smooth outside of vtec. Also, before the bike warms up and im below 150°F (when VTEC gods are not satisfied with the environment,) im able to rev all the way and wow it is quite smooth after all the work I've done but when the guage reaches 150° right on que, vtec sputter or VTEC cutting in out begins. Lets say im doing 50mph and im approching 6400rpm but just befor i get to it. I down shift and let the clutch out so that i blow past the transition into VTEC. And now the force of the rear wheel is turning the motor and im on standing throttle...It will hold and vtec is deffinatly engaged and not cutting in out. I can remain in vtec but its throttle dependant. Too much throttle and it will start to cutout. So if that happens, i can let off the trottle,,,,lets say 10% and the engine recovers and remains in vtec until i let the RPM drop back down. Then its the same process all over again

    So what next.
    MAP?
    https://www.google.com/search?ei=69...KexIogJ6g#scso=uid_BN9oW6CzKOGV0wLX2JTYAg_0:0

    I really wish i had the ECU test harness with the breakout connectors. Does anyone have an alternative thats not so expensive.

    Question can i just relace the ECU with a used one from another 6th gen or is there a process that needs to happen. The one i got from the 2009 seems like its for a compleatly differnt bike. When i start it. LOTS of misfire, even at low RPM. ..

    I really aprritiate the time and effort folks.
     
    Last edited: Aug 6, 2018
  7. skimad4x4

    skimad4x4 "Official" VFRWorld Greeter

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    Certainly the breakout test lead identified in that schematic would make fault finding a whole lot easier as inputs could be checked with the ECU hooked up and operational.

    However the lack of any fault codes being generated suggests this is an intermittent/dynamic issue where the ECU receives what appears to be a normal sensor input and the ECU which simply tries to respond as programmed.

    In the absence of the test lead shown on the schematic, perhaps get the multi-meter out and start measuring values from each individual sensor / cable input to the ECU to see if they are in the specified range. Also check for chafed cabling or loose connectors to pertinent sensors - as something as simple as an intermittent short to earth or a loose or intermittent break in a wire can deliver abnormal inputs to the ECU.

    Certainly your video suggests this is an electrical issue with the ECU simply responding to very choppy on-off inputs which would suggests a short or wire break.

    I would definitely stick with the ECU which worked OK for a while - these things are pretty bullet proof - I have never heard of an ECU failing without obvious external cause - like a serious voltage spike.

    Start by removing the fairings to get access to the ECU (its on a bracket tucked up below the headlights)
    Then disconnect the ECU from the multiplug and test inputs on the multiplug. Where possible test with the ignition off - as this may reveal a cable shorting to earth.

    Carefully check the inputs from those sensors which are known to prevent vtec engagement but would not stop operation below vtec range - so ECT and IAT are the obvious ones to check they are in the specified range.

    As for swapping ECUs I am not sure it is a good idea. Certainly there are big differences in the ECU programming between the pre 2006 ECUs and 2006 onwards ECUs so definitely avoid earlier ECUs.

    Then there is HISS - ECUs from HISS equipped models wont swap as they only work with input from the HISS sensor when a suitably coded key is present to fire up. - I am not sure if the 6th Gen VFRs sold in the USA ever came with HISS, but that adds a whole heap of extra complexity if your bike is HISS equipped. Fortunately it is easy to tell as the HISS reading assembly is clearly visible as it surrounds the ignition key slot and has the word HISS written on it.

    Obviously if the later ECU came from a HISS model then I am surprised anything worked at all.

    Finally Power commander - Inherently they aim to mess with the ECU to make it behave differently. Whilst the Power Commander should be pretty reliable it may be defective or affected by other related adaptations like fitting O2 eliminators. Hence if your checks come up blank I would be tempted to see if the bike will run fine without it. In essence remove the Power Commander and revert the system to standard - so reinstating O2 sensor and PAIR flap valve connections which presumably were simply disconnected somewhere from the ECU. If the bike then runs OK then you know the culprit.

    Let us know how you get on.


    SkiMad
     
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  8. Diving Pete

    Diving Pete Member

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    Have you checked the pair valves..?
    Will it hold at 5000rpm - before VTEC engagement?
    Does it do the same RPM drop when in GEAR (riding)?
    Also agree - remove the Power Commander - It does not aid in troubleshooting this.
     
  9. Diving Pete

    Diving Pete Member

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    What is the status of the PAIR valves? - open, closed, connected, not connected. - Pictures do help as you have had too many people looking at this & now you really need to start from step 1 - if only to ensure that its all connected up correctly.
     
  10. lonnieleyden

    lonnieleyden New Member

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    Hello Pete! Thanks for responding. pair valves eliminated, not connected, vacuums pluged. O2 eliminated. Powercommander was only installed temporary to satisfy my own curiosity but sinse have put it away until this issue is sorted out. Will put the pair valve back and O2s back in action sometime this week just to have a steady baseline. However, they have only been eliminated for 3 weeks now. Pair and O2 mods were done recently after i sincronized the throttle bodies. Issue same before and after.

    currently the bike is down to bear bones with all faring removed exposing most sensors, solenoids, wireing harness. I been probing with a DMM for days checking mostly the sensors themselves per the 2002 manual. So far everthing checks out okay. Spool, ECT, Neutral switch, IAT, ECR, FCR, IPG, CPS, coils, valve timing. And alot more just need to go to work now so will let you know when everything is back to stock
     
    Last edited: Aug 7, 2018
  11. lonnieleyden

    lonnieleyden New Member

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    Smooth as butter before VTEC no issues
    Under 150°F when vtec will not kick in.. bike runs great at all RPM.

    Yes when in gear amd riding.

    I know i wrote alot in my original posts but all of this is mentioned there.

    Thanks for your help.
     
  12. lonnieleyden

    lonnieleyden New Member

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    Yeah I've checked most of the sensors themselves but not at the muticonnector.
    It actually sounds much more relaxing then climbing all over the bike disconnecting sensors to test. Im gonna put the bike back to stock and tidy things up a bit and will carefully probe the multi-connector.
     
  13. signal

    signal Definitely Not New Member

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    Not sure if you are still battling this issue.

    The issue would appear to be your camshaft timing is off. This is possibly due to previous work that has been done to the bike, perhaps it got botched during a CCT replacement. Here is a thread that explains this same problem as you experience, Page 3 is where things get fixed.

    Please keep us posted!

    https://vfrworld.com/threads/2007-vfr-is-crapping-out.27213/
     
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