It may be 2 wires rubbing together, it may be another wire grounding out, it may be a loose/broken coil in the relay, it may be burned/melted contacts, it may even be as simple as a loose relay. The fact that you're activating it with the key off makes me think that the negative side of the control coil is being grounded out. That technically shouldn't affect drivability, it would just mean that your computer is on all the time, regardless of key position.
But yea, you're going to have to take a look and maybe swap relays around, look for damage in the connectors & wiring.
Hiya Natenkiki!
So, I took the PDB fuse box off today. Underneath it was the relay housing. Tapping on that with my hand even lightly would make the FPR activate. I noticed this only happens with the key in the ignition (not turned at all)... not with the key out. What is the difference between key in and key out?
Interestingly enough, after taking the relay housing off and wiggling all the wires and relays around, etc, I couldn't replicate the problem.
Either it was a loose relay like you mentioned, or I got unlucky with the positioning of the wires.
It started to rain of course, so I put everything back. After it all being back together, I was still unable to replicate the issue. I wonder if it'll come back.
Next on the diagnostic list was the TPS.
Get this:
Having everything plugged in (MAF, TPS, IAC), the car stalls either right away, or soon after starting.
You already know this; unplugging the IAC stops it from stalling right after startup.
However, here's something I messing with today.
Keeping the IAC plugged in, I tried unplugging the TPS instead. Interestingly enough, it idles very nicely. In fact, it idles the best it has in a few weeks... unfortunately it idles a bit high (about 1200 RPMs).
HOWEVER; with the TPS unplugged, if I give it too much throttle, it stalls right away. Therefore, it's undriveable that way. I can slowly rev it up and up and up and up and up.. but if I give it a lot of throttle in one go, it stalls. Keep in mind this is all at idle.
So, symptoms in a nutshell:
- With everything plugged in properly on my truck, it stalls right away.
- With the IAC
unplugged, I can get from place to place okay, but it'll stall occasionally at idle or when not applying acceleration rarely.
- With the IAC
plugged in, but the TPS
unplugged, it'll idle like a dream (albeit a bit high), but I can't give it gas or it'll stall.