Confirm my brake issues from symptoms, please

Hi y'all. 2004 Tacoma V6, AT, 4WD, 250k miles.

When coming to a slow complete stop, such as parking spot or stop sign, the truck will brake gradually as normal but then the engine will rev and the truck will lurch forward right before it stops.
-I have not been able to reproduce the engine surge while in park or neutral by stomping on the brake or pressing gradually or quickly repeatedly pressing the pedal. When I do stand on the brake, it is firm at first then very slowly sinks.
- I have not found any vacuum leaks and the engine idles as normal
-Brake pads and rotors appear to be in good condition but I haven't taken the wheels off for a proper inspection (Tundra disc brake mod).
-Brake fluid reservoir is full.
-Right front ABS speed sensor is throwing a code but has been for an issue for a year now. For some reason that sensor and my front right blinker do not get any power at all, but that's a different can of worms (I think!)
-10*F outside but dry roads, defrost(AC compressor) may have been on
-This truck has been my daily driver for 16 years now in all weather and I have never experienced this issue.

I plan to replace the brake booster, master cylinder, vacuum lines, flush my brake fluid, and check for leaking brake line fittings. Those items need to be replaced on age alone, but somebody please shout if you think my brake surge could be anything other than that. Thanks!

 

I have no idea what's up with your truck, but here's a few thoughts... If the engine revs why is it a brake issue? If you're getting an engine surge while slowing down I'd be looking at something with AT or throttle, not brake fluid. What happens if you just coast in gear to a stop without applying brakes? Or drawing the parking brake to stop? Does the engine rev then? What if you brake hard vs light...? Try the other AT gears and see if this is consistent across everything. I'd be looking for consistency and inconsistency to further isolate the issue. GL~

 

OP I bet your brake booster is starting to fail. A vacuum leak in the booster while depressing the brake pedal can cause an increase in rpm. If it’s the original one it’s probably time to replace it. If you do go with one that has the master cylinder already installed on it. Pretty easy job to do.

 

There are some quick tests you can do simply to test brake booster

https://youtu.be/QaUPC8TjzWA?si=fBqYgTYCLeqeWknX

 

Thanks for the replies. I'll get to this in about a week after a work trip and report back.

 

I replaced the brake booster and master cylinder. Now my brakes are soft but I think I just need to bleed more air out of the system. New stainless steel brake hoses are on their way, too, as my rubber hoses are original to the truck.

 

And did this solve the engine rpm issue?

 

Make sure the rear brakes are adjusted properly

 

To me it sounds like something with the transmission. I had a similar issue with a GS300 I had and it was the throttle cable that needed adjustment which made the transmission kick when I came to stop. It felt like someone would bump into me in the rear if that makes any sense. I doubt your issue is brake related. Check the ATF.

 

Not enough drive-time to tell. It wasnt a predictable/intentionally-repeatable event.

 

Hey great tip, I'll check on that.