bjt1ngle

ok so I built a stroker, modified k24 crank and inline pro rods for oem pistons. supposed to raise the CR to 12.8:1
well I noticed it studdered a little yesterday (I finished the build Sunday) and threw a cel. all the misfire codes. and some o2 sensor code. so I replaced all the plugs with ngk and swapped my coil packs to a secondary set I have just to try and I'm still getting p1399 and a blinking cel
I haven't driven it since replacing the coil packs. just idle and after a minute it'll blink and go away. I replaced all my vac lines because It sounded like a leak and I also threw a secondary air pump code. which hasnt come back after that.

any suggestions or ideas? running rc 650cc and a walbro 255 with a vafc II. stock cat.

bjt1ngle

also I got new springs retainers keepers and valve seals. may need to adjust the valves ?

b.r.i.a.n.

vafc II?

get rid of it. the vafc II maybe ok for a stockish bolt on setup but in your case you need a standalone.

4bang6

your running a stock ecu with a vafc??? on 650's??

bjt1ngle

I already know that. I hate myself for passing up on an AEM for $400 a couple years ago, I've been lookin for a good deal like that since then. done enough research to be comfortable with the apexi for right now, I'm not driving it at the moment, I have a daily. I'm still waitin on my wideband to come in before I do any tuning with it

bjt1ngle

like I said, I've only put about 30 miles on it since I turned it over because it seemed to idle smoothly and it's driven smooth with the two exceptions of it bogging for a moment around 2k-3k

4bang6

^^^^^What b.r.i.a.n. said^^^ you need fuel management and tune-ability, NOT a VAFC

bjt1ngle

I've been in touch with a few people who did a stroker and ran a vafc for months with no issue and eventually did upgrade to a full ems.
so with the bashing over the vafc I'm assuming you all have come to the consensus that it's a fuel problem causing the misfire?

b.r.i.a.n.

well you've already changed those injectors. those injectors don't have the same dead times as the stock injectors. you're going to be chasing your tail trying to tune the fuel map with the incorrect dead times.

besides that, the vafc will remove fuel. considering you've lengthened the stroke, you're going to be doing the opposite lol. i don't understand how you can cheap out on the one thing that will tie everything together.

bjt1ngle

I only needed to move the car out of the way for right now, I'm planning on leaving it with a vafc. with it being mechanic tuned I figured it'd be like everything else and work as is for all I needed. I wanted to make sure the Clearence was good and there were no leaks, so the vafc has worked precisely as I needed it to. I knew the limits of it before I got it, but someone sold it to me for super cheap and I figured it would work for what I needed for the time being and it has.
I'm just trying to make sure that's all it is, and that it's not something worse before I spend a grand on an ems and it still throws these codes.