2002 A4 1.8TQ (B6) Tip - 27k - Can anyone explain how the "Engine Brake Boost" works? I am having an issue when my car automatically shifts from 2nd to 1st when the car is stopping and I am using the brake (does not happen if there is no pressure on the brake pedal during the downshift), sort of a little lurch, it feels alot like a little brake is being let go. If the Brake Boost has nothing to do with the symptom, I am still curious as to what/how it works.

Also, does someone know the fuse # associated with the ABS Braking System? If I find it and take it out and drive for a bit, I am guessing that it will throw a code and a waring light will appear. If I put it back in, will the waring light disappear after a while? I am getting a VAG in a few days, so I could clear the code? I want to make sure my lurch has nothing to do with the ABS system or this "Brake Boost" thing. Thanks alot for any thoughts and information!

My dealer nor AoA is being helpful, but the issue is there. I'll find out the problem on my own!

Oh, I also got an APR Snub, it will go in soon...maybe this will help my lurch - but hope to get smoother shifts, etc. anyway. Fingers crossed.

 

the car should shift to 1st when u stop that seems rite casue the transmision ecu doent want u to stall, i think that lil breaking feel is just the car down shifting

and what is brake boost never heard of it

 

Engine Brake Boost is in my manual under "Brakes." I think it said the system works on a vacuum or something - yes a mystery to me as well. I do agree Panda, could very well be the trany creating the lurch feeling during downshift - but it is pretty pronounced and not normal. I have driven cars just like mine and my car has an issue - friends who drive with me feel it as well.

 

The master cylinder (big old black cylinder near the firewall on the drivers side) provides a huge multiplication of the force applied to the brake pedal to engage the brakes. Basically, you can apply minimal pressure to the actual brake pedal and the master cylinder multiplies that force many times in order to engage the brake pads on your car. That's kind of an over simplified explanantion, but that's the general idea.

 

mister technical over

 

Hakes, please let me know what your VAG reads out...and how you solved the problem...I am curious...I am having a similar sensation although it is not always that noticeable...I have an error being addressed wednesday regarding the brake boost that my VAG pulled...I'll let you know how that turns out...I do not think the problem will trigger a CEL...

 

I'm with you sebass - can't wait to get the VAG.