Engine dies when brakes applied??!?

[snicker]

I am still trying to debug a problem with my engine stalling. I have checked for any vacuum leaks and don't believe there are any. This is a brand new engine + transmission. The transmission has had some problems and misc parts replaced but that is all believed to be fixed now.

The problem first showed itself when idling at a red light the car would die. It would immediately fire right back up and drive fine as long as I could hit the gas.  Idling + brakes kills it everytime      

To test vacuum leaks this afternoon I removed and plugged the vacuum line from the engine to the brake booster. The car then started up and idled fine in park and neutral. I could put it in drive and leave it chocked against a curb and the it would idle lower but would still hang in there UNTIL I hit the brakes and it would die right away. I reproduced this several times with the same results. This would also happen in reverse...brakes applied...car dies.

What is the connection? We removed the vacuum hose from the brake booster to the engine so that should make the brakes isolated from the engine correct? What is the correlation between brakes an idle speed?

I first suspected it was an electrical short of sorts but wouldn't that be manifested when the car was in park and neutral as well? This also doesn't happen when the car is at high speeds. I really need to get this figured out because the car is garaged until I can chase this gremlin down.

This is a 69 Dodge Charger with a 360 engine + 727 transmission

[TylerCharger69]

Wow.....even with the booster unplugged it still does it huh?  Only thing I can think of immediately, it maybe our vacuum reservoir canister located under the battery tray.  Not sure though....it is a mystery....I'd like to know what it was when you do track down that gremlin.  Maybe vacuum going to the headlight switch?  I'd say....try plugging off the entire manifold vacuum completely to where it is totally isolated and then see if it does it.  It could be a PCV valve issue too (positive crankcase ventilation). If those things don't help you....well....someone here will have the answer...I'm sure.  Keep us posted!!!!.......Ace

[snicker]

I forgot to add that I've isolated the headlight canister from the brake booster as well and sealed off the PCV valve.

[squeakfinder]

 
Sounds like your RPM's are dropping to low when in drive sitting still. Have you tried adjusting the idle?

[Purple440]

 

What is your idle RPM in drive?  I used to have this problem until I got the vacuum gauge out and tuned it up.  Timing+idle mixture

[1969chargerrtse]

I had this issue on my restored car.  My 140.00 positve cable had a fault in the head connector at the battery point.  The thinner wire that went to the bulk head connector was disconnecting in the positve clamp.  If I was at a light at idle and hit the brake the car stalled.  I cut the main thick wire sheild off and cut the thinner sheild wire off and wrapped  a solid piece of wire around the two and soldered it.  I tapped it up and haven't had the problem since.  This may not be the same as yours, but that's what happened to me.  Bottom line was the positive feed to the fuseable link was disconnected so the car powered itself off the alt direct, but at an idle the brake bulbs drained it down and it stalled.