Brake pedal Pulses when stopped while in Drive or Reverse. Not when in Park

New to me 2005 Tacoma TRD Sport (automatic)
So far, I have two hopefully minor issues. One is, when at a standstill and in Drive or Reverse I get a pulse in the brake pedal. It feels like an ABS activation but obviously I am not moving. Normal braking feels perfect no sounds, no vibrations. At times it vibrates enough that it can be heard as well.

This happens at stop lights or even in the driveway before even driving away. Once in Drive I get a vibe/pulse in the pedal. It's like the brake is sensing a load on the system and activating some pump/motor/actuator.

I have searched the forums and I only find threads on warped rotors, ABS speed sensors or brake booster failures.

Anyone, have an idea?

It does have a 2010 4runner caliper with 2010 4runner Stoptech front set up. Stock rear drum brakes. All pads, rotors and disk look fine. Any help is appreciated.

 

Welcome to TW

 

@HondaGM appreciate the help

 

You actually feel the ABS activating stopped?..

 

Sounds like a failing ABS module, no lights on in the dash?

 

I am not sure that is what it is, it is just the only way I felt like I could explain it. I don't think it is actually the ABS. I am thinking its maybe the brake booster or a vacuum issue or something causing the brake booster acting weird. What throws me off is the brakes actually work great for their intended purpose. No vibe, no pulse, no sounds. It just an excessive amount of pulsing just in the brake pedal when stopped. It typically takes a few seconds to start the pulsating. At a stop and once the pedal becomes stiff it begins to pulse.

Maybe is a transmission or diff issue that is translating to the brake pedal when with a load yet stopped. Not sure

@Bishop84 no lights on the dash

 

Does the engine surge when the pedal starts pulsing?

 

No engine surges, no lights, no other symptoms. Pulsing brake pedal is all, but I’m a perfectionist I guess and it’s strange.

 

Let me think for awhile…

 

I mean on the surface it sounds like possibly a failing brake booster but I would expect there to be a hissing noise or other symptoms as well.

 

Does the idle fluctuate when it happens? I'm thinking possible vacuum leak at booster, maybe it just hasn't coded yet.

Where is the idle rpms when this is happening? Is it super low? Try cleaning the throttle body

 

Describe the pulsing more -- esp, how fast is it? How many times per second, can you count, or is it too fast to count? If it's too fast to count, is it fast enough to make a low "hummm" sound? How strong is it? I.e. is it subtle, something only a sensitive driver would notice? Or is it loud/strong dead obvious no matter who the driver might be?

 

So just went out to try and count. It’s too fast. It’s maybe 5 or 6 times a second. It isn’t a hmmm. It’s a very pronounced tap, pulse, vibe. It’s like a sound from a dewalt electric impact wrench, kind-of..sort-of.

When sitting in the driver seat it sounds and feels like something tapping on the brake pedal or maybe something hitting the firewall in front of the brake pedal. It goes away completely when it’s not at load so in neutral or park it is gone.

engine rpm at idle around 900 steady.

 

I would suggest disabling ABS in order to easily rule that out if it still does it. There are quite a few threads on here with how to disable ABS on the fly with a simple switch if you want that, or can just pull a fuse temporarily to diagnose while still being fully reversible. If I remember correctly there's two fuses, 50A and 30A and you want to pull the 30A, and your ABS/VSC/TRAC/ whatever stuff your truck has will be disabled until you put it back in.

 

Pulled the ABS fuse out and pulse/vibe is still present no changes. I’m thinking it’s exhaust or something rubbing on a linkage or something somewhere that is translating only to the break pedal. Unsure.. I’m kind of at a loss.

 

Well that rules out that. I would think the same in terms of exhaust or something else, unless something really weird is going on with the brake booster. I could see an increase/decrease in pedal stiffness and stuff but such a rapid tap/pulse would be weird considering it just runs on simple vacuum. I'd start reaching/crawling around touching stuff while in park and see if you can isolate it lol, maybe try an auto stethoscope or screwdriver up to your ear if you don't have one.

 

Are your rotors drilled?
Our HHR had what I called warped rotors. they pulsated. Worst after my wife drove it and would subside a little after drove it for a while. I just drove it until the brakes needed replacing and I replaced the rotors and pads. Currently, I have no pulsating.
I replaced my rotor on Victory with a similar rotor as stock. I say similar as they both are drilled, but what I noticed on the replacement, is that the holes are not chamfered. Often when I brake I hear a rapid clicking sound when I brake. My assumption is the noise is coming from the rotor when moving under the pressure of the pads.

 

OP described the problem as also occurring when the vehicle is parked / not moving. So -- probably not the rotors.

 

Sorry, I guess I missed that.

 

May be a leaking brake booster (using more manifold vacuum than normal). Were the symptoms present before you did the 4Runner big brake upgrade?