what could be causing this? This happens during accelleration , it chuggs a few times and is very sluggish. On a live data monitor the front O2 sensor seems to vary alot in the monitored voltage reading while the secondary is steady at around .750 or so . I replaced the O2 sensors yesterday and the accelleretion improved somewhat but it is still very sluggish and the miss is still there while accellerating. There is no miss during idle or steady driving and there are no starting issues. I can provide limited data from my scan-tool if more is needed. Does anyone have any Ideas where to look at next?

 

Has the timing belt been replaced?

 

yes my son had it changed a couple of months ago.

 

The timing might be off then. I would check that first.