hi i have a problem with my apex vafc engagement adjustment...i use to have it at 5700 rpms and now it makes my engine light go on all the time and won;t let me engage vtec...my vafc was street tuned with wideband02 and proffesionally tuned...i know for sure its the vafc problem and nothing else cuz the car shop that i go to checked it out and we disconnected the vtec wire from vafc off from ecu and now engine light is off and working fine...anyone else had this experience and problem with the vafc??

 

It can be many problems...but are all your setting correct? Like is it on 4 cylinder? with the arrow pointing to the upper right corner? If your VAFC is soldered to your ECU...are any open wires touching other wires?

You might want to also pull the code to see what it says...but if it was working fine before, maybe you should take it back to the shop where it was tunned and installed to see if they possible made a mistake.

 

Is the VTM lead hooked up? The V-AFC installation guide implies that this lead is optional, but it is required on the S2000.

 

Check for any kind of loose connection in the wire splices.

 

I had that problem.. and i do know whats making the problem.. your keeping your self in vtec while just crusin which is not good do to being low then 5900. You have to reset your ecu to get the check light off. Plus if you do race from 2nd and your trying to stay in vtec room a roll.. DONT! it will mess up your motor and plus your give to much air flow which the ecu cant handle. Then you have to reset it again. in other words... wasted money.

 

yea...that happened to me when i installed my VAFC also. It didnt occur much but every once in a while( maybe like once every other month) it would do that. I noticed it cuts my vtec off when i stay in vtec for a while, like the guy in the post before me stated. Also when i was pushing my car hard for a long time it cut off and then a couple times it would just occur randomly. Its very annoying. I would just reset my ecu and it would run fine.

 

I dono what your saying...are you saying that by using a VAFC...you can't shift at redline and stay in VTEC? Cause...this will someone damange your engine and cause you to have a check engine light?

I have had a VAFC in my car for...2 years and I've been to track events and I drive it hard sometimes (Redlining all the gears throug 3rd...end 4th) And I have never had a problem. No check engine light...nothing. Are you saying I'm causing harm to my engine by doing this? How? A VAFC (if not tuned) Dosn't change anything on the car...its just a like a guage that reads your throttle, RPMS, voltage etc... I dono how having one in your car untuned can cause any harm? Granted My VAFC is tuned...but either way it shouldn't have a negative effect on your car unless some functions are off.

 

I sc my S with VAFCII and have the same problem if i stay right at Vtec for more than 15 some seconds. I think our ecu is too smart that it tries to match the map (fuel) with ignition timming and the vtec point is not excetly the same every time. Since my map signal is a lot different than the NA S, I have more problems in matching the fuel with the timing.
If i am on highway and dyno, both conditions are fine. I have trouble on the track because i stay at Vtec point a lot!
I just disable the Vtec function and it works fine.
Did you have a lot of mod. and aggressive fuel curve which might be the mis match problem? Might be the high low thr% problem too, since the half thr. giving me the truoble.

 

ya it happened to me while goin in a wide turn staying in vtec mode for like 10 seconds or so...my car shop who tuned it said it will happen sooner or later with the vafc...they also said it screws up with your map sensors dealing with the vtec and could damage your ecu...meaning the vafc is just not smart enough to trick the ecu..so i also did what u did...took off the vtec wire from vafc and now it is fine...i will eventually get rid of it when i buy a aftermarket ecu...and yes my car has quite a bit of mods too..i just want it tuned a safer way goin towards a standalone route

 

Your tuner didn't set up you VAFC right. If you aren't at WOT (>80% throttle), then the VAFC shouldn't be doing anything to the MAP voltage. Even if it did, it wouldn't damage the ECU. The VAFC's default 10 / 50 throttle settings don't work well for the S2000. I found that 80 / 81 does perfect.