car wants to die when braking.

[C. Senor]

i just installed a cam a little more aggresive that stock (262 duration), now after finally getting it to idle decently, and not bog out when starting from a stand still, the car wants to die when i brake. it seems that when i brake the brake booster takes away or gives to much vacuum (not sure what it actually does) and makes my car dip down to 500 rpm, idle is set at 1200, a bit high but i cant make the car idle better, any lower and it's kinda funny. but anyways i was wondering if anyone knew any solutions to my brake booster taking too much vacuum? thanks in advance if you have any possible solutions and for taking the time to look.

[sebazztard]

if it only happens when you brake, and you have to have your idle that rediculously high to stay running, im betting there is a loose vacum line or one you overlooked when reinstalling everything. thats my guess anyway.

[mazdaRX7Galantvr4]

It's possible you could have a rip in your brake booster diaphram. It probably isn't a coincidence like that. I'd recheck your vac lines and clamps on your parts.

[C. Senor]

thanks for the replies guys, but i did that yesterday night, i loosened everything up and retightened all of them, i thought i might be doing something wrong and had my brother look, and everything seemed ok. but i'm going to check my vacuum lines...its weird because if i''m idling and i pump the gas pedal really quick the rpm's go up about a thousand.

[g6civcx]

Check all vacuum lines.

[TheTimanator]

It's possible you could have a rip in your brake booster diaphram. It probably isn't a coincidence like that. I'd recheck your vac lines and clamps on your parts.
if it was his brake booster you would be hearing some noise when you press the brake and the brake feel would be very different...sorry for the lousy description, this happened to me last year.

[HalveBlue]

Check FSM.

My car used to stall upon deceleration after I'd drive it hard. This stopped happening after I recirc'd the BOV.

Also, check the big vacuum hose that runs from the engine to the brake booster. Also inspect the check valve that connects the two.

Good Luck!

[Dream240]

It's possible you could have a rip in your brake booster diaphram. It probably isn't a coincidence like that. I'd recheck your vac lines and clamps on your parts.

A problem like that with a booster will cause it to fail and you will have an extremely hard pedal. Since he's not describing that it's a vacumm problem elsewhere.

It sounds like you have a problem with the idle vacumm. The root of all idle vacumm comes from your intake. Check your intake piping hoses and, also check the small vacumm hoses that connect to your throttle body and IACV. Sounds like you have a clogged hose that's preventing idle air to circulate. thus the need for you 1200 rpm high idle. The higher the idle the more air you have flowing into the intake. Your idle shouldn't be above 800 and that's pushing it. I would go to your local auto shop and buy about 3' of 3/8" vacuum line then go into your engine bay and start pulling off old hoses and checking them for flow I guarantee you, you will find at least one hose that's completely clogged.

I have found 3 on my intake system so far....and I'm still checking them little by little. The S13s are old and having petrified hoses is not uncommon.

GL

[los_inc]

also use intake cleaner and run it' through the vacuum hose that goes to the "iacv" make sure you give it a little throttle so it does bogg down and die
also replace you "pcv" valve it helped me idle better after abusive driving.
-los

[C. Senor]

cool, i'll be sure to check that asap, thanks for everyone's help i really do appreciate it.

[harlockssx]

What kind of engine management are you using? If you have a BOV vented atmospheric with stock engine management, the cam swap may have pushed you over the edge...an SAFC would be a cheap band aid, or recirculating the BOV...

[C. Senor]

i'm not boosted, so i dont have a bov, and have no engine management, the only thing i have on the car is intake, cam, and headers....also i was trying to figure this out today, why would a vacuum problem present it's self only after putting in a more agressive cam?

[sebazztard]

thats just the thing i was saying b4, i dont think its related. cam has nothing to do with your brakes, brake booster is ran through vacuum and if your problem is with your brakes and the reason for the high idle its vacuum... i have the same problem currently dude...havent had a chance to do a run through with the hoses but im betting its iacv related. there was a writeup on it here to spray some intake cleaner through one of your hoses, i cant wait to try this when warm weather hits cuz ive had this problem for abt 2 years now :) maybe you can help me out :p

[idlafie]

Check for a parasitic power drain - try hooking up a voltmeter to your battery. You should be reading 14 volts as the motor is running. Step on your brakes & see if the voltage drops down to 12.5 volts or less. If it does then you've got either a). a bad battery, or b). a voltage regulator inside the alternator that's starting to go bad. My buddy's '95 S14 has the same problem. His car dies when his motor's decelerating & he's stepping on the brakes coming to a stop. He's also got a bad valve cover gasket so he could also be suffering from a vacuum leak too. Not sure..I'm still trying to figure this one out.
Keep me posted...
ID

[harlockssx]

thats just the thing i was saying b4, i dont think its related. cam has nothing to do with your brakes, brake booster is ran through vacuum and if your problem is with your brakes and the reason for the high idle its vacuum... i have the same problem currently dude...havent had a chance to do a run through with the hoses but im betting its iacv related. there was a writeup on it here to spray some intake cleaner through one of your hoses, i cant wait to try this when warm weather hits cuz ive had this problem for abt 2 years now :) maybe you can help me out :p

BTW, the cam has a LOT to do with the vacuum your car makes. More radical cams have more overlap, which reduces the amount of vacuum you make at idle & low RPMs...for this very reason a lot of drag cars that use power brakes require an additional vacuum reservior, as pictured here:

http://store.summitracing.com/partdetail.asp?autofilter=1&part=SUM%2DG1460&N=700+%2D45701+115&autoview=sku

[drftwerks]

its vac leak, check char canister and vac line in intake mani

[gonzoes14k]

odd, i had this same issues when i did z brakes, turned out to be bad tps ..good luck

[C. Senor]

i just want to say thanks for everyone's input, i'm going to leave the car as is for now, since now in school and working i dont have too much freetime. but eventually i will check stuff out, possibly try the brake assist pump thing, i will post when i do figure out whats going on.