I've heard some about the "vafc jerk" and I think I've got it fixed on my car. I have an automatic, so I'm not sure exactly who else has the problem. But the problem I had was when you let off the gas while your cruising down the highway, and then when you get back on the gas, it jerks becuase the computer screws up the fuel mixture.
Anyway I figured the computer had a second idle program (becuase I know it idles different in park than it does in drive, becuase I can look at my a/f meter and tell). So what I did was I put the car in park and revved it to 3000rpm (anywhere around there is ok). I noticed that after a few seconds it jumped around all over the place. So I thus determined that *this* must be the problem. So I richened the mixture (at partial throttle setting) until the computer would no longer lean out the mixture (the jumping was caused by an intermittant lean mixture). I got all the way to about -30 (up from -39). SO I drove around and noticed that for a minute it was ok, but then it came back. So I retested, and determined that the L.T.F.T. had adjusted (leaned it out) over the period of a minute or so causing it to jump around again. Thus I revved to 3000 again and continued richening up to -25 where it stopped bouncing again. Now the jerk is gone, and it didn't happen for about 2 hours of driving.
Now the problem is that the curve is too high to boost very much. I will overcome that obstacle when I come to it, but I'm pretty sure that I will use the 'Load determined vtec' in the vafc. I'll set the default vtec crossover to 4500 (closed loop begins) and then set the auto load transfer to 0psi (or wherever I decide works best). That will give me an easy 'boost map' to get rid of all that partial thottle increase and make sure the CEL doesn't come on if there is boost during partial throttle. This will fix the problem (I think) becuase the vafc will put the car on the 'vtec map' whenever the car goes past 0psi, thus giving me a seperate 'boost map'. Great isn't it?
Be in mind that I don't have vtec, so this setting won't actually DO anything, it will just serves to give me a free different map that is used only under boost.
Btw: I have some odd throttle settings, I think I have 72% for WOT and like 20% or so for partial (I'm not sure that matters, but I'll check tomorrow)
Hope this helps anyone who has had this problem, Tell me if it works for you!
Anyway I figured the computer had a second idle program (becuase I know it idles different in park than it does in drive, becuase I can look at my a/f meter and tell). So what I did was I put the car in park and revved it to 3000rpm (anywhere around there is ok). I noticed that after a few seconds it jumped around all over the place. So I thus determined that *this* must be the problem. So I richened the mixture (at partial throttle setting) until the computer would no longer lean out the mixture (the jumping was caused by an intermittant lean mixture). I got all the way to about -30 (up from -39). SO I drove around and noticed that for a minute it was ok, but then it came back. So I retested, and determined that the L.T.F.T. had adjusted (leaned it out) over the period of a minute or so causing it to jump around again. Thus I revved to 3000 again and continued richening up to -25 where it stopped bouncing again. Now the jerk is gone, and it didn't happen for about 2 hours of driving.
Now the problem is that the curve is too high to boost very much. I will overcome that obstacle when I come to it, but I'm pretty sure that I will use the 'Load determined vtec' in the vafc. I'll set the default vtec crossover to 4500 (closed loop begins) and then set the auto load transfer to 0psi (or wherever I decide works best). That will give me an easy 'boost map' to get rid of all that partial thottle increase and make sure the CEL doesn't come on if there is boost during partial throttle. This will fix the problem (I think) becuase the vafc will put the car on the 'vtec map' whenever the car goes past 0psi, thus giving me a seperate 'boost map'. Great isn't it?
Be in mind that I don't have vtec, so this setting won't actually DO anything, it will just serves to give me a free different map that is used only under boost.
Btw: I have some odd throttle settings, I think I have 72% for WOT and like 20% or so for partial (I'm not sure that matters, but I'll check tomorrow)
Hope this helps anyone who has had this problem, Tell me if it works for you!
Well almost, I know that there is only one table that you modify on the ECU for your fuel map, but it does change; it doesn't just ignore the other sensors after it gets to 4500rpm or 72% throttle. (Sorry if that's not what you meant, but thats how I read it.) It takes the numbers and multiplies them by something to acheive a rich mixture so you can have better acceleration. I don't know exactly what it's going for becuase I don't have a wideband.
