If my 83 S is idleing at like a stoplight or something and i pump the brakes the rpm's drop off almost below the bottom mark on the tach, if I pump then hold the pedal down the rpm's stay that low and the engine spits and sputters in an attempt to stay running. Does this mean i have a vaccum leak or what? I tried pumping the brakes at idle on the TA and the rpm's go up. I assume thats what is supposed to happen. If anyone can shed some light on this problem i would greatly appreciate it. TIA

 

Sounds like your break booster is out of wack

 

yes, vacuum leak at the break booster. pretty common my car does the same thing. nothing to worry about considering the fact that locating the leak is almost impossible.

do the lights dim also? how about when you run accesories such as heat and A/C? You might have a weak alternator or battery.

 

Sounds like your engine's running a little too lean at idle.

It's normal for idle to change when you PUMP the brakes. That's how vacuum boosters work - it's a diaphragm with vacuum on both sides. When you push the brake down, you allow air (from the passenger compartment, incidentally, which is why it makes a pssh noise) onto the back side of the diaphragm and this helps push on the master cylinder. When you let off, the valve closes and another one opens to equalize the vacuum on both sides of the diaphragm.

So when you pump the brakes, you're basically using the vacuum booster as a foot-operated vacuum leak.

 

Every rx-7 I ever had done this, and my brakes were fine. If you rapidly pump the brake at idle, the rpms drop down...

 

Thanks for the replies guys. So is there something i can adjust/replace/fix to make it not drop so dramatically? The only reason i really asked this to begin with is, on a cold day, when the engine is warm enough to kick the choke off, but not fully warmed up, just pushing the brakes, and disengaging the cluch (i.e. stopping at a stop sigh) causes the car to die instantly. Once it warms up for another few minutes its fine. Thanks

 

Nope, just put a 80 amp alt in last weekend and the battery is a year old, so my electrical system is in great shape. Thanks anyway though

 

82Transam said:
You're supposed to take it out of gear before you let it out... j/k

BrianHeston

 

Disengaging the clutch is pushing the pedal DOWN

Try richening the idle mixture a bit. The fact that the problem is worse when cold supports this.

 

You might also try hitting it with the timing light. I had a really bad problem with idle until the car was completely hot. Would constantly die. She was a few degrees off, once I adjusted it, she doesn't stall out when cold anymore.

 

Just tried it on my 88 vert, pump the brake quite a few times quickly and the car tried to die, I think this is normal for 7's...

 

Thanks for all the info everyone. Guess I'll have to richen it up a bit and check the timing. I just put new plugs, plug wires, and distributor rotor on a few weeks ago and still no luck. Thanks again, I'll keep everyone updated.