Hey, y’all. 2007 XLT 5.4L with 206k miles.

There have been a few times when, around 75 mph, the speedometer jumps around a bit and the throttle gets a little bogged down.

A few days ago it happened again but was much worse. Speedometer suddenly dropped from 75 to 35ish and I thought I was losing all power. My speed was still around 70 but the speedo jumped all over the place. The throttle felt very bogged down and the wrench indicator light kicked on. I dropped my speed to 60-65ish and made it home without issue.

Autozone scanned the light but it had turned itself off and they were unable to read any history.

I’ve had the P0420 cat converter code on for quite a while but it has been running pretty well before this. Is this likely the cause?

Thanks for any help, truly appreciated.

 

Have your exhaust system back pressure tested. It sounds like you have a clogged cat.

 

If the speedo is jumping around, sounds like you have a speed sensor issue. This will affect the speedometer AND how it runs, you have an electronic throttle.