i just got through searching and i found alot of answers to my questions but i am still confused. i have the zex nitrous system with the msd digital window switch. In Zex's installation instructions, they tell you to connect the white wire to the output voltage lead on the tps. i connected the white wire to the blue wire of the tps at the throttle body like the directions said. now whenever the activation switch is off, my car idles at around 1300 rpms and the throttle position sensor reads 6 percent. when i turn the activation switch on and the window switch comes on, the car idols fine and the tps reads 0 like it should. does anyone know what could be causing this problem? is the voltage from the tps backfeeding into the zex box? any help would be greatly appreciated. thanks.

 

also, the msd instructions say to have the box set on 1 cylinder for the ls1 engine. when it is in the 1 cylinder mode, the rpms on the box do not read right, they only read right when they are in the 4 cylinder mode, i have read that people leave them set on the 4 cylinder mode but i was just wondering what the difference was, if any.

 

to the top. any help is appreciated.

 

Wire in a relay that is grounded by the window switch that controlles the tps wire on the zex box and that high idel should go away.

 

Yes it is and the solution may be a 9.6k resistor in-line from the TPS signal wire to the NMU. You can call ZEXTECH (which is COMP Cams) and ask for Rich. I am having the same problem but my NMU has failed and am awaiting its return so I can see if this problem was with the NMU or that I need to add the resistor. Mustang people have been experiencing the same issue.

 

JFYI, I was told to NOT use my aftermarket ignition window switch with the ZEX kit but do a direct connection to the chassis ground and let the WOT switch control things. I'm not too happy with this limitation so what I have done is to create a new ground circuit using the Mallory window input wire.

I have the Mallory window switch complete a circuit that activates a 30 amp relay that in turn completes my ground to the ZEX solenoids in the NMU. I have also inserted a simple 1 amp diode in parallel with the window ground and +12v power wire to this relay to catch any current which might find its way back to the NMU. I hope this is some help to you.

I have a Mallory 685 Hyfire and a ZEX 82026 wet kit.

 

YOu can use a relay to break the connection on the TPS wire or hot wire etc, of call Zex they have their own window switch.
Ricky

 

98redorangeta
do you have the zex kit and did yousolve the idle issue with the relay?Do you still have the kit? hows it working? Is it a quality system? Sorry for highjacking this thread.

 

I have tryed that relay, you still have the rpms jumping up, My MSD Window Switch had tAKED a dump. Sent it back for repair.