Alfa Romeo Forums banner

'83 - Brakes drag down idle??

878 Views 5 Replies 4 Participants Last post by  Alfacliff
New to site, purchased an '83 Veloce after not having a spider for about 8 years. Been through IAP manual & Bosch L-jetronic injection idle adjustment & tune up page I found from reading threads on this site. I've diagnosed about everything except when I hit & hold brakes, the idle drops drastically causing it to die. I realize it has something to do with the vaccume hose from the plemum to the brake booster but can't figure out whats going on & why it drags down the idle?? If anyone has insight on this help would be appreciated greatly. Also, fixing to adjust valves as they are noisy - anyone near Topeka KS with a shim kit??

Thx Matt
1 - 6 of 6 Posts
Sounds like the brake booster has a leak. pull off the vac line and plug it and test. The seal around the master cylinder to the booster could be bad too.
Normally (well, not normally really as it's a malfunction) vac leaks from the brake booster hose or pancake cause the idle speed to go up when the brakes are applied as the leak is introducing air in a fashion that is akin to cracking the throttle open a small amount. (usually 200-300 rpm increase)

That aside, a horrific vac leak in the brake circut can cause things to drop right off too, as the bigger the leak, the less metering the AFM will do. (all the air comes in a different route than normal so the AFM starts to close up resulting in a really weak fuel mixture)

While you're looking over the hose and booster, check the one way valve at the plenum end of the vac hose onnaconna if it sticks open it'll also cause some goofyness in the way things work when on the brakes. (up to and including a pulsing brake pedal)


Check the valve lash before getting all excited about shimming them til they are quiet. There is a certain amount of clatter involved with this type of engine even when they are well within spec.
See less See more
European car co in wichita has lots of shims and other parts, they have been an Alfa dealer and service for years, I used to get parts from them in the 70's and they still work on and race Alfa's.
Thank you all

My one way valve checked ok. I could not do the IAP Manual brake booster check b/c it would not run long enough to see if the pedal went up or down. I finally took the brake booster out of the loop and all is good. I just capped off the booster and plenum, I do not notice much if any change in the braking. I thought when I bought it you had to use a lot of pedal pressure to stop, apparently the booster is just bad. Pedal pressure is about the same as my '71 Datsun 510 road race car (for sale by the way as I can no longer justify the extreme expense being a grandpa 5 times over now).

As to the shims, I'll have to check next time in Wichita, I thought I heard the Levian's had closed Eurpoean car. Maybe next weekend I will check the clearances & if nothing else, just order what I need from IAP.

Thanks again for the input. Great site. :D Matt
still open, I will check, I think they may have moved though.
1 - 6 of 6 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.