AF Learning Changes With Amount of Gas in My Tank???
I have yet to find another case like this. 02 wrx, 4eat, stage 2 ots tune. K&N panel filter, STi up pipe, Perrin catted downpipe, no other related mods. DP was used, new o2 sensor when installed withdownpipe 1.5 years ago. MAF has been cleaned more than once and done delicately.
So my AF Learning 1 has always showed me running rich. As low as -8.xx lbut not all the time. Lately Iclve been seeing as low as -11.xx. The weird part is with a full tank it gets as low as -11 and as the tank gets lower the af learning 1 gets higher but now at a half tank its gotten much worse and will stay as low as -10.xx at about 40mph and I wanna say somewhere around 3k rpms.
I have a bad DP rattle against my tranny crossmember and it might be causing a leak from literally beating the exhaust bolts loose. I also get knock events if I drive below 40 mph in 4th gear(overdrive, its a 4eat auto l, remember).
So what the hell is going on? A bad fuel pressure regulator or fuel pump? Bad o2 sensor? I really am lost here. Im very broke right now and have to get my timing belt done before i can get a protune shop to help me. I could never find a boost or vacuum leak but maybe i missed it? I also get a light but consistent stumble if I really get on it and stay on it at higher speeds. Where should I look? Thank you so much in advance. I am concerned.