A/F going nuts, Need help!!

JunkieXL · 12-09-2007, 03:02 PM

Ok, heres the problem. I recently installed a Fmic, 14b and a handful of other goodies, and have been slowly working all the kinks out. I had most of the issues (boost leaks ect) taken care of, but the car still ran pretty rough, and i kept getting fuel cut/misfire at WOT. Now i pulled the plugs and found two were extremly rich, and a couple showed signs of knock (little white flecks on the electrodes). Swapped them out for a brand new set of NGK's gapped to 28. Now i just drove the car for the first time since then, and i'm a little freaked out, i was cruising on the highway and noticed the A/F cycling into the rich randomly, only a blip for a second then it would resume its normal stoich settings. Odd, but not a problem. Then after pulling onto a side street I decided to see if the car was still breaking up/hitting fuel cut under WOT/full boost. Held the car about 75% throttle through second and third and it seemed to pull well, no signs of breaking up. Let off and had the car in 4th crusing. Within about 20 seconds i noticed my A/F cycling rich again, only this time it was also dropping extremly lean for a second. It did this twice, cycling back and forth until i put the clutch in, took it out of gear, and began coasting in neutral. After putting the car back into gear, it seemed to be staying within its normal range for off boost cruising, although i only drove it another half mile or so till i got to my girlfriends house.

Sorry for the novel, i'm just trying to make sure i didnt leave anything out. Cliff notes version is
A/F randomly cycling well out of normal range while cruising, causing noticable studdering/loss of power for split second. Car idles slightly lean, about 14.9 to 15.3, and takes a second to come back into idle A/F ratio after coming to a stop.
At the moment, the only other known issue i'm having with the car is a boost leak at the TB i havent addressed yet, but i doubt that could be the cause. In addition, the car has a MAF, MAFT setup, but its zeroed out. 14b is being run at wastegate pressure

Forgot to add, car has about 84k and is on stock fuel

JunkieXL · 12-09-2007, 04:12 PM

anybody?

timloomis · 12-09-2007, 04:21 PM

You could have a bad o2 sensor, your datalogger will tell you that. Your maft is "zeroed out", when I had the maft I actually had to tune in the 450's. Every car is different so even though you have a stock fuel system, it still needs tuned. The gm mas flows quite a bit more than the stocker too. Your boost leak at the tb could be causing it to run lean for a second too.

JunkieXL · 12-09-2007, 04:37 PM

I had been wondering about the 02. I havent checked it with a DMM yet, but i figured since the car wasent running rich constantly, or getting bad fuel mileage, it probably wasent the cause.