Fuel cut problems

[TheStuartKid]

Just recently my car started jerking really bad under load.. When i first start the car up from a cold start over night and when I'm under load shifting through my gears. I watch my dash hawk as its happening the STFT is at -25.8 and the car sputters bad. Also i am getting 15 mpg now. I was expecting to get a worse average mpg but not that drastically. I am so confused on what it could be so can i please get some feedback. I at first thought it was something with my fuel pump (maybe being dirty when we installed it), possibly thought i needed a tune, and now I'm thinking it could be spark plugs. IF anybody has had this problem or knows somebody that has please get back to me before i start spending my money on pointless stuff to fix it.
I really appreciate it.

 

[MSMS3]

Maybe tell us your current mods and post a datalog? Not enough hard data in your post.

 

[TheStuartKid]

turboxs catless downpipe/racepipe, mazdaspeed CAI, cobb TIP, PTP HPFP internals, and hypertech tune. i will post a log tomorrow.

 

[MSMS3]

Try to do a single gear pull at WOT from about 2800 rpm to about 6500 rpm in either 3rd or 4th gear, if possible. I want to see where the cut or ignition miss is taking place. Log rpm, fuel pressure, boost, afr, kr, throttle position and pedal position and g/s maf air flow at a minimum. Injector pulse width, too if you can. It may not be fuel cut.

Edit: I'd also like you to give us some info about what the LTFT's are at idle and when just cruising around at part throttle.

And, lets go back to basics. Do you have a recent datalog from before the problem arose. That might help us see where the change or changes are. And I'd want to know what your mod setup and configuration was the very last time it seemed to run properly and each and every change, adjustment or other thing you've done under the hood since then. Chances are this is something simple that arose in connection with some mod change, service, adjustment or other activity under the hood. Always begin by thinking what has changed in any way from the last time it was running fine. That may not lead to a solution, but it's a good beginning point.

 

[TheStuartKid]

thanks man for all that, im going to get back to you in the morning with all that, but i can tell you right now my mods never changed under the hood when the problem occured, i was up at school and it just slowly started getting worse and worse...

 

[etipp98]

if your stft's were fine and are now suddenly going to 20+ then your purge valve may be bad.

 

[TheStuartKid]

I figured out what it was, after jerking really bad my car threw a CEL and it said my o2 sensors were pushing low voltage for too long... took out my first o2 sensor and cleaned it and it went away.

 

[MSMS3]

This leaves unresolved the reason why the sensor was fouled? Fixing the symptom without knowing the cause may result in it coming back.

I note from another thread thay your fuel mileage has gone down dramatically. Did cleaning the sensor fix that too? Running excessively rich, for whatever reason, may have been the cause that the primary (wideband) sensor fouled, or conversely, a fouled sensor could have been sending faulty into to the ECU and causing the excessive richness. Dog chasing its tale. If both issues are resolved you might want to report that on the other thread so we can quit trying to offer suggestions regarding possible causes of excessive fuel consumption. Just a thought . . .