RPM Dropout

[Chandar8]

Howdy everyone, it is time to consult the Tbird hivemind. Shit bird has had an issue where when I try and go full throttle itll randomly drop out RPM and then come back into it. Occasionally on cold mornings itll do it as well at around 2k but this is less consistent. The car idles normally, generally drives normally and feels fine. This has only started happening after the PI swap.

 

[1997ThunderbirdLXV6]

That looks exactly like my tach when I was going through that whole crank sensor code episode. Do you have any codes?

I have a thread about it. It came back every few months until one day, the car was completely immobile. I ultimately replaced the entire crank sensor wiring between the sensor and the firewall connector. I also got a new PCM around that time, so it's not entirely clear what fixed it. I'm just glad it's fixed!

 

[Chandar8]

That looks exactly like my tach when I was going through that whole crank sensor code episode. Do you have any codes?

I have a thread about it. It came back every few months until one day, the car was completely immobile. I ultimately replaced the entire crank sensor wiring between the sensor and the firewall connector. I also got a new PCM around that time, so it's not entirely clear what fixed it. I'm just glad it's fixed!

No codes at all. I did re use the crank sensor from the previous engine so maybe its just not playing well

 

[1997ThunderbirdLXV6]

In my case, replacing the sensor didn't do anything. The sensors aren't fragile; the wiring apparently is.

 

[Grog6]

That wiring is a pain because it's a tiny signal, and if you break the foil shield in the harness by flexing it, you get no signal. It's a "twisted pair" of wires, in the harness, with said foil covering them. I'd try a new sensor first, making sure there's no debris stuck to it. It is a coil of wire and a magnet, so shit can stick and kill the signal. Old sensors lose magnetic field over time.
If that ain't it, you gotta strip the harness back, and verify it to the eec.