Misfire and lumpy at low speed

[keatsie]

A couple of additional issues have raised there heads.

My 400 se won't idel well and hunts with occasional attempts to stall, on light throttle the engine is very hesitant and jerky - fees like a heavy misfire. Open the throttle and all seems fine - any pointers?

[pwd95]

There's two types of injection system on the 400's. The later type (hotwire) controlls the idle with a stepper motor on the back of the plenum which can be unscrewed & cleaned. The earlier type is a bit more involved. Saying that, the idle on my old 400SE & my current 450SE is very lumpy because of the wild cam profile, could just be that.

[keatsie]

Thanks for that, but the engine misfires and jerks at light throttle but I will check the stepper motor

[pwd95]

Had a missfire on light throttle before, ended up being the throttle position sensor.....