Tps 89 jaguar xjs marelli ignition

does the red wire have to be connected? when its connected car wont run right. when I disconnect car runs good. Maybe wire going to ecu has a bad connection? not sure if I can drive without being connected. Thanks for any help
[date=2018-06-13 time=22:36

Runner43,
The Yellow wire on the Throttle Potentiometer goes to EFI ECU pin# 19 for the ground signal, the Green wire goes to pin# 20 for the positive voltage, and the Red wire goes to pin#7 for the variable wiper voltage.

All three Throttle Potentiometer wires need to be connected to function properly and provide the proper signal to the EFI ECU for fueling.

Maybe your Throttle Potentiometer is misadjusted or broken?

Try searching the archives for Throttle Potentiometer to see if any of the many discussions about failures, test, and adjustments of this part can help you out.

Paul

He can’t be talking about the red wire on the throttle pot, can he? All three wires to the pot are connected with a single connector, he’d have to cut wires to disconnect the red one only. Is that what’s going on?

If so, I suppose the issue could be a bad throttle pot. It’s supposed to provide an electronic equivalent of an accelerator pump, helping the engine respond to throttle changes. When throttle is steady, it shouldn’t do anything. If the track is bad, it could be breaking up and giving flaky signals, which in turn dumps fuel into the engine when not needed. And it might even do that when you’re not touching the throttle, just reacting to engine vibration.

Simple to check. Connect an analog VOM (digital VOM’s don’t work well for this) to the red lead and one of the other leads, put the VOM on an Ohm reading, and slowly move the throttle from idle to WOT. The resistance should move gradually and steadily with it. If it breaks up, pops from open circuit to closed, the pot is bad.

The connector on the car to the pot was bad so i put connectors on individual wires to make connection. Thanks for the help I will look at it this weekend.

Paul,
I adjusted the pot started and ran good for about 5 minutes. It was reading .36 when running when it started running bad it read .01. Maybe Im doing something wrong but followed steps from kirbys book. I think the pot is bad but if not im not sure what it is. I did a sweep test and it did look like it was jumping around a little. thanks for any input.