Something new, can't figure it out.

A few months ago we did a hard panic stop almost missing an exit on an empty highway. We spaced out, slammed on the brakes, but made the exit.

Brakes have been normal since with one exception, 0-5 mph parking lot stops. Normal stopping is all regular, traffic lights, etc. However, pulling into a spot, you gotta almost stand on the pedal. Backing out, no issues, same speed. Around the parking lot 5-10mph, all normal, no issues.

If the pads were glazed, or rotors blue, all stopping would be compromised, nope. Just very slow stops.

I have read a failing booster would lead to this, but from my experience, it's all or nothing, right?

I'm randomly getting misfires and bank one too lean codes. CEL comes and goes. Stumbles when starting for a minute, then evens out. It does have 150,000 miles on it.

I have started to suspect a vacuum hose from the booster maybe, only at idle? Does that sound right? If there's a leak of unmetered air, that helps with the misfire, but why would it not affect all braking and a/f mixtures at all times?

Ugh, enough guesses, anyone have any ideas?

 

Is this a Cooper? Check the spark plugs, you may be due. Bad plugs can cause your misfire and mixture codes. These cars are extremely finicky when it comes to air leaks, so if you had a vacuum leak I would almost guarantee there to also be an unmetered air code, not just a system lean code.

As for the brakes feeling undesirable; have you pulled the wheels and checked the pads at all 4 corners? You may just be due for brakes, the boosters and vacuum source for the booster aren't really a problem on these cars.

Short of that, when is the last time you had the brake fluid changed? Air in the system or broken down fluid will impede braking quality.

 

Yup, 2010 regular cooper

Did plugs about 2000 miles ago.

I gotta search for vacuum leaks, but no codes for unmetered air, just misfires and lean codes. I also get a random p173b AFTER I replaced the thermostat (see other thread for this annoying car)

It's 0 degrees here and I have no garage, so I gotta wait for VT to defrost so I can pull wheels.

Yeah it's probably due for a brake fluid change too, but how would that affect a 0-5 mph stop and not any issues with higher speeds?

 

Just ordered a vacuum pump rebuild kit on Amazon. All the research I have done point here. If the pump is broken, I'll replace it.