Misfire under hard acceleration?

I have an 89 supra turbo. lately under hard accel i have been getting some bad misfire and loss of power.. one guy on the street said he saw sparks coming from my exhaust when it was misfiring.
the car is somewhat modified and had little problem up until recently
it also doesnt seem to misfire under 10psi of boost but about 12-14psi at higher rpms causes bad misfire. any ideas?

I have an 89 supra turbo. lately under hard accel i have been getting some bad misfire and loss of power.. one guy on the street said he saw sparks coming from my exhaust when it was misfiring.
the car is somewhat modified and had little problem up until recently
it also doesnt seem to misfire under 10psi of boost but about 12-14psi at higher rpms causes bad misfire. any ideas?


Do you have a Wideband o2 in the car? What are your A/F ratio's when it misfires? What plugs are you running?

your air fuel might be off, but more likely it is your plugs. Try running a hotter plug. In MKIV's we run NGK 3330's, you can pick them up at www.boostlogic.com for a good price.

Ron

when this happens does your "engine" light flash on and stay for a second or two? if so, your most likely hitting fuel cut-off which is a toyota computer controlled measure which actually turns off your fuel so you dont detonate and wreck your engine, if your car is modified what have you done to it? if you put a bigger turbo in or changed your afm then your car is recieving a lot more air than should and with stock injectors your fuel system cant keep up.