only does it when the engine is cold. on light but sharp throttle tip-in engine misfires for a half a second, then it pulls normally. during this short hesistation period afr jumps to 15.5-16.0
after engine warms and reaches ~50-60*C the problem is gone

suggestions please. any mechanical fault or something rom related ? using 96530706

 

that sounds normal, mine does the same thing on cold start, she gets pig rich and starts to misfire. Let the car warm up before you drive.

 

I said it goes lean, not rich

 

the ecu is compensating for the rich mixture.....

 

Normal, happens when I dont warm up my car properly. /

 

so, noticed next thing: the problem occurs even when the car is pretty much warmed up, ~80* C. when cruising at 2500-3000 rpm and 14.7 afr, tipping the throttle in, spikes afr to 15.5-16, even 17's sometimes. just for a second, then it recovers to normal burning process again.

what do you guys think, does it more look like to firing problem or fueling ? and what can be the cause

 

Who dialed in your injectors? What do your fuel trims look like?

 

myself
its's an Evo3 with E8 ecu. injectors are stock 510's, scaled accordingly
maf tables also rescaled so that actual afr and map afr are pretty close to each other

can't tell fuel trims, low and mid arent working due to early evos have unheated O2 sensor

 

Hmm, have you done all the basic procedures like boost leak test/ exhaust leak? I know when I shift it will go lean like yours but only until the o2 catches up. Mine will stumble, bog, and lope but only until its warm.

Try:
Maf cleaning
Spark plug change
Voltage / olhm test o2
Boost leak/exhaust
Resetting /reflash Ecu

 

check your flule table , in the light load on the rpm base that you are running when missfire ,
and ad some fule , and make a pull and check the AFR .
As said abvove check of you have and kind of leaks , esxhust , vacum,
fint out why it missfire before you load the enginge hard,