High Idle While Applying The Brakes (Video).
 

Wondering if this is normal or no ?!, While sitting at idle I pump the brakes a couple of times and the rpm will increase 200 : 300 rpm.

Based on the MILs and the empty fuel tank, I think a couple hundred RPMs when hitting the brakes is the least of your worries right now.

Thank you sir, That was really helpful :rolleyes:

But you could be more helpful if you tried this in your car to see if it's doing the same !

Car has no MIL, It has a full tank of gas but the level sender unit gets stuck.

Sounds like your brake booster has a vacuum leak.


- Check your brake booster vacuum hose for leakage.
- Check the gasket between master cylinder and brake booster for leakage.
- If the leak is internal, the booster will have to be replaced. Take it to Nissan or a reputable shop to diagnosis this.


(can't watch your video where I'm at)

Mileage? Mods?

Well, FWIW, I checked mine out of curiosity (6MT, 2008 Touring). Didn't see any change outside the normal RPM fluxes in open loop whenever I hit the brakes. You can check the booster with a fairly inexpensive vacuum pump. Here's the FSM procedure for a 2008 (yours may vary depending on your year; check your appropriate FSM):

1. With a handy vacuum pump, apply vacuum pressure of –66.7 kPa (–500 mmHg, –19.70 inHg) to the brake booster.
2. If the air tight condition cannot be maintained, perform the following operation.
3. Check the no dirt and dust are present on the brake booster and brake master cylinder mating faces. Clean it if necessary.
4. Check O-ring on the master cylinder. If anything is found, replace the O-ring. (Model with VDC)
5. Check the air tight condition again. If the condition still cannot be maintained, replace the brake booster (models with VDC) or brake booster and master cylinder (models without VDC).

Could also be a bunch of other things (like a failing alternator that's loading up when your brake lights go on).

Honestly, the video you posted is pretty bad at helping us get a sense out of what's happening because there are so many extraneous issues going on as well as the RPM surge.

Thanks zakmartin & Atreyu'z 350 for your help.

Car is 05 with 80K miles.

Today I replaced both brake booster vacuum lines, The one at the booster & the one with check valve, But it's still doing the same.

I checked the fuel trims while pumping the brakes and I can see the AFR going too lean.


Good point on the alternator, Will disconnect the vacuum line going to the manifold and try.

If it's reading too lean, you either have unmetered air going into the engine or you have a clogged injector (or a weak fuel pump). Getting a fuel pressure reading and going after air leaks would be my next course of action before swapping out any more parts.

Check the intake after the MAF sensor and make sure everything is buttoned up tight.

How much time did you give the car to warm up when you took the live scan readings?

Just to clarify,

You mean it could be a vacuum leak somewhere else (other than the booster) ?, Even if it leans out when applying the brakes ?