rpm drop during braking

[russ240sx]

When I brake, and I am in neutral, the tach drops to about 300-400 RPM, then when i take my foot off the brake, Idle goes to back to normal ~700-750. This doesnt happen all the time, but it has been getting more frequent lately. I have never heard of anything like this and I have no clue what is going on.

Also, my car has 165,000 miles and the transmission, clutch, and engine are on the way out, and the driveshaft has some play in it. What do you guys think about keeping the car and fixing it up or selling it and getting an s14? I would have about 2 grand to spend to fix it, but i dont know if the money would be better spent towards a newer 240.

[gyfer]

That's normal.

[NeedCAforS13]

mine does it too, but I'd really like to know why? I'm SURE the car didn't do this straight from the factory?;) I mean, mine's dropped down to like 100 on occasion, and has actually stalled out once or twice! It hasn't been acting up in the last 6 months, so maybe I fixed it with the last service I did to it (filters, belts, oil, general cleaning, etc...):)

Sean

[GroundZero]

my car did that too until i replaced my altenator drive belt. check that first and replace it if necessary. let us know whats up.

[xdreamz]

BRAKE LIGHTS PEOPLEdraw power, loads alternator, slows engine,basicly, Ground z, the prob will be back.. and the rest.. expect to need an alternater within 6 mo.s

[gyfer]

The vaccum draw from master cylinder brake could contribute the "rpm drow" too.

[xdreamz]

good spot gyfer

[gyfer]

thank you

[kandyflip445]

May be the brake booster. Check the check valve. Find the hose that runs from the booster to the intake mani. The valve should sit inline in the hose mounted on the firewall. All you have to do is blow into it and see if it lets air through. If it's clogged replace it. (there should be an arrow on it or the mount pointing which way to blow though it)

[p00t]

test the check valve like kandy said, also check the brake booster hose for cracks and leaks.

this is gonna sound weird, but i had that problem and redoing the engine grounds with beefy wire, and cleaning/removing the aiv fixed it (check the sticky).

but could be the brake booster, keep us updated.