Rough idle, brake booster

[FransB85]

Hi I thought it would be nice to share with you all I have finally resolved an issue I had with the car since I got it in 2010.

Every cold start my car would have problems with rough idle, dropping down almost to the point of stalling, and shuddering like a washing machine with a brick in it. I have inspected, refurbished, cleaned, re-tightened and replaced a lot of components of the fuel system (fuel lines, idle control valve, FPR, injector seals, vacuum lines, AFM, inlet gaskets). Being 27 years old, most of these items were on my 'to check/do list' anyway, the problem remained, though.

It was somewhere this summer I realized that the issue would start right around the moment I would depress the brake pedal. Also, I noticed a hissing sound coming from the pedal box when applying the brake. Finally I put 1 and 1 together and realized there would probably be a substantial vacuum leak in my brake booster.

I replaced it and voilą! the issue has finally cleared! As a bonus my brakes feel about twice as effective, especially when slowing down to a standstill, the brakes stay on a lot tighter (I drove home in the rain after replacing the booster and blocked the wheels at the first traffic lights)

there is no good write up on the internet about replacing the brake booster, but it is pretty straight forward, just take out the seat so you can work lying on your back a lot easier, the firewall insulation has holes where the nuts are, you can pop out the rubber grommets. Use 2 long extensions and a knee-joint for your socket.
have a friend help you so you have someone to hear yell and curse, it's much more therapeutic.

Now I can go about fiddling with the idle adjustment with my new digital laser tachometer!

Take Home Message:

If you are chasing a vacuum leak or rough idle, don't forget to check your brake booster.

[Ga 951]

Thanks for the info Frans. Glad you got it sorted out! Thank goodness I don't have this problem...looking at the parts side ~ $1100 to fix a vac leak (for my car)...........OUCH

[FransB85]

luckily my car had the ATE booster, about $260. but it's a b*tch to get to...