stalls shifting into reverse?

[Mike_D1980]

97 5.4 runs like a top, but sometimes when coming to a fast stop, it stalls. And when shifting into reverse most of the time it stalls then too. New iac, so don't think that's it. Does idle low, like 500 rpm and sometimes at a red light while idling fine, the tach will just drop to zero and sit there til I give it some gas.
any ideas?

 

[Mike_D1980]

no one? What sensor tells the tach what the rpms are? What else does that sensor control is it tps?

 

[panda24619]

did you check that boot behind the throttle body along firewall? mine used to do that before i changed that elbow boot. now idles fine.

 

[Mike_D1980]

so, the iac "looks" new, but when I unplug it with the motor running there is no change. Does that mean it is bad?

 

[panda24619]

could be. might want to replace it. then if thats not the problem then someone would know myabe tonydiv would. hes better at these things.