stepper not working

[nick jenkins]

Hi all, Still can't get stepper working. does air temp,water temp tell ECU what to do and control the stepper. On the hand held I have noticed sync error with random numbers, also  cyl = y sync = y which is correct, but every now then sync=y at random times I get a NO showing up in split second its gone but its there. I also took the stepper out and  stepped the stepper motor to the open position so I could get Idle to no effect I still can't get an idle.  

[Simon]

Hi Nick

ECU uses engine temp, throttle position, and engine RPM to control idle.

If it think the throttle is open it will lock the idle out. Same if the RPM is too high (above 1500 from memory)

Engine should idle even if the stepper is not functioning but open.

In this case the sync/cyl can be ignored as it will not be having any negative effects.

[nick jenkins]

Have fitted new stepper motor and this only steps closed.  Have rechecked wiring.  Now have taken ECU out and looked at motherboard.  Notice that there is a series of resistors that are burnt starting at R89, R90 and R88 and possibly R91.  What do these resistors control as appears to be where the stepper motor board is plugged in???? Could this be causing my problems and shall I return ECU for further investigation.

Nick

[Simon]

R89 is connected to Purge control.

R88 is AC clutch

R90 is Fan control

R91 is water spray.

If however these are burnt to the point of being open circuit it might have damage further down the board.

Its at the point it might as well come back to us. For a going over on the bench.

[nick jenkins]

Hi Simon, I'll get it away asap and let you have a play. Nick.