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paul77


paul77
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hello new hear  i just fitted my new exhaust on my gen 6 now i dont have vtec  and i dont no how to fix  please help  and many thanks in advance 

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I can’t understand how a full exhaust would, in itself, effect the VTEC. My understanding is that it is predominantly controlled by oil pressure change, which an exhaust should not alter. There is probably also a bit of “electrikery” involved, that might best be explained by Grum and others. Given that you would have had to plug and unplug a few things, to get the old headers out, and new in, you should first check all those things are back as they were.

 

 I’m as much of a mechanic as I am a rocket scientist, so take anything I say with a grain of salt. Others here will chime in soon!

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I suspect that something was intentionally or unintentionally unplugged to aid in the installation. 

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Agree with above, you may have disturbed something with the install, or you're expecting it to operate below the required engine temp. Perhaps your exhaust mod has had a positive effect on the smoothness to 4 valve ops!

 

Is your engine temperature indication normal and your Fi light off?

 

VTEC ops relies on.

- Sidestand switch.

- Coolant temp above 65degC 149degF.

- Engine rpm above 6800.

 

The VTEC spool valve is mounted in the Vee and if you disturbed its wiring you would most likely force a Fi Fault Code of 27.

 

Guess there is always a chance the spool valve is jammed closed! You may have to get access to the valve located in the Vee to do some checks re Service Manual.

 

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IIRC, if the VTEC solenoid that actuates the valve is not connected, it results in a no-start.  That, however is quite unlikely as the connector is very difficult to reach under the throttle body.  A thermostat stuck open keeping engine coolant below the threshold Grum mentions could be one possibility.  Often in trouble shooting an alteration is made and the presumption is  that it's cause and effect when a fault is noticed.  The likelihood you disturbed anything VTEC related in the process of R/R'ing the headers is quite low.    Could it be that you've ridden it around a while and not noticed that it wasn't working and then after installing the new exhaust, in the moment of enjoying it decided to let it rip and only then realized the issue?  Or as Grum mentioned, maybe you're just not noticing the change to 4 valve operation now vs previously.  I'm not sure there's any way to objectively verify that it's working other than the seat of the pants method. 

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On 1/13/2022 at 11:22 AM, Cogswell said:

I'm not sure there's any way to objectively verify that it's working other than the seat of the pants method. 

You could fairly easily measure the VLC Solenoid voltage supplied from the ECM.

There is a 6P Sub harness connector that sits just above the left radiator. The single Green/Yellow wire of the VTEC Solenoid goes through this connector. You could probe the wire at this point with a voltmeter WITHOUT unplugging the 6P connector.

Stick the bike on the center stand, side stand up, warmup the engine and run the engine above 6800rpm. You should see 12v appear on the Green/Yellow wire when all the VTEC criteria are met. That would at least establish the ECM is working correctly.

You might need to run it up whilst in gear as speed and/or neutral switch might also be an unwritten criteria.

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