Thread: AFC Neo problem

When driving at part throttle, around 40-48% throttle it leans itself out and falls flat on its face for a few rpm then goes back to normal only at the rpm throttle points, up to 4k... (set at 500rpm increments starting at 750, 1000 then 1500, 2000 ect.
Any clue as to why it is doing this? I have a code for knock sensor which I'm going to replace since I used the stock VE one..

Please, no responses such as "get a calum, or real time or blah blah blah" I have a 94 g20 ECU in it and thats what I have the money to really work with
WOT runs perfect

Get an analog voltmeter and hook it up to the tps. Slowly roll the throttle checking for dead spots.

TPS is fine, only happens at afc throttle points..

Can you move the problem area by adjusting the ne points? The ne point increments you have listed above are very close together, I have never needed to have the ne points like that for a strong tune. What is your setup and does this issue occurr at all engine temps?

Do you have a wideband? Id try running without the afc..


Then later... down the road... when you can afford it... get nismotronic..

It sounds like you are transitioning from the closed loop to open loop portion of the MAP and the O2 sensor is no longer making fueling adjustments for you in those areas.

Who knows though without actually logging the ECUs short term trims and other relevant data.

I'll have to try moving the points and it does seem to happen at all engine tempatures.. I have a sr20ve


Yeah it pegs the wideband to 19 (highest) but sometimes it just jumps up and down from 14 to 16 when it does it. No AFC means running lean as can be at idle / first thousand rpm(19) and running pig rich when pegging it lol (9, lowest it goes)



Best I can do is use a snap on ethos and monitor the sensors for now =\

Something has to be off with the setup. Like fueling issue or bad sensor. On a stock g20 ecu with ve 333cc inj. You should be able to just pull 10% out across all ne rpm points and have good results. What maf are you running?

Well on WOT it does take around -10% and goes as much as -16% when I had it dyno tuned. I know I've read from others running a g20 ecu they had to add fuel at idle

Well I turned the low throttle point down tot 7% and it stopped doing it then back up to 8% (where it originally was) and it still is not doing it... No clue why =\
Lol the SSAC header has a spot for the wideband and the bolt in it, well I was driving and it came out LOL super loud exhaust :X