5 volt sensors on xfi not working.

NVR2MCH · #1 (**permalink**) 08-13-2010, 01:16 AM

I have a 93 mustang with a fast xfi. I had it at the dyno recently and at full throttle the tps sensor was jumping from 95% to 65%. I also had a iac error code, map sensor reading was way off from the dyno reading, and cts is pegged out at 255. they are all 5 volt sensors right?? I have been told it could be caused from ignition interference. Could this affect all this? The car doesnt idle right and also surges during driving. I can not cruise at a constant speed. I need some help please. The fast system was just rebuilt, so it is new. I dont know what to do.

TurboNova · #2 (**permalink**) 08-14-2010, 11:48 PM

Sounds like you have a harness problem. Not all a 5v reference.

Map has a 5v
TPS has a 5v
CTS and IAT both send voltage out and measure resistance back
IAC is a PWM output to turn the IAC in and out, it is not 5v

Some of this could be EMI Ignition interference, this is usually caused by ignition or other EFI wires coming into contact with spark plug wires, MSD boxes, coil wires, distributor trigger wires. Anything that pulses and has high energy is a problem if it comes in contact with the EFI wiring.

The distributor trigger wires and coil wires are the worst.