car not running right...

Originally Posted by ecoli

If it still has the automatic ECU, then it is tuned for 390cc injectors. 450s aren't a huge jump so the O2 sensor can probably still handle it, but the jump to 550s might be too much.

In closed loop the ecu can adjust for larger injectors up to 40% in 91+ and 30% in 90s IIRC but I am almost certain in dsms that when the ecu switches to open loop under hard throttle it is running off pre-programmed maps and the fuel trims do not update or have any affect on the fuel being injected. Correct me if I am wrough though, the dsm cd doesn't go into detail about it.