: dropping rpm when brake

12-02-12, 12:06 AM
had this problem over a year now ((
time to time when i brake and stop my rpm dropping to 200 or so, usually happened when im preforming stop and hold my brakes longer then usually, like if u coming to red light, 200 rpm remains for like 1 second or 2 and then rmp raise to normal 500


12-08-12, 03:01 PM
Any Idea?????

12-13-12, 01:36 AM
Come on?, someone out there must have had this problem and fix it, I have it too, but have no idea ether, any suggestions?

Thank You

12-13-12, 05:18 AM
Not on a Catera, but I had the same thing happen years ago.
It was a vacuum leak, related to the brake booster, can't remember if it was the check valve, hose, or booster.
If I remember correctly, somehow, when you applied brake, the vacuum would go to "uncontrollably open"(?)
Think I had to replace the booster due to a vacuum leak.

Regardless, it sounds like a Vacuum leak to me, and the reason it appears while braking leads me to advise you to start at the brake Booster.

Might try plugging the Vac. line to your brake booster first, then isolate each seperate vacuum line until you find the culprit.

12-17-12, 12:54 PM
ok what is a brake booster? and where is it located?

12-17-12, 01:12 PM
It's the large, round component between the master cylinder and firewall. Inside, is a large diaphragm, that uses engine vacuum to provide power brake assist.

12-18-12, 12:48 PM
OK, got it, so how does that, have to do with engine RPM dropping up and down sometimes, I can,t see that its even connected to the engine, if there was a leak in the vacuum there, then it would effect the braking system and not the RPM right?

01-06-13, 12:25 AM

01-06-13, 01:53 PM

01-08-13, 10:23 PM

01-09-13, 12:06 AM
Maybe IAC or TPS. As far as I know would cause idle problems.

01-09-13, 05:48 AM
in my case it started to do way more now, approx. every fifth stop or so....
According to my research it related to air lost due to broke mane rubber seal in booster, i personally swap twice throttler body in pass year (got used from junk ward) they both worked the same, (guys IAC and TPS its one unit for 2000 sport, call "Throttler body" its $400 peace). that's not the problem!!!!. Brake booster $100. i would personally replaced next day, but i have All Data when i looked on procedures... i change my mind to do it, it's just to mush to do

so any idea?

01-09-13, 10:07 AM
In my 2000 the IAC is mounted to the TB at the rear by the firewall it's got a couple vaccum lines connected to it. I have a similar issue, the car idles high at start cold or hot at around 250-300 and takes at least 1 minute to idle down and even then it stays above 1000 until I take off but while driving it fine. this also causes a hard shift. On a kinda warm day I will try to clean the IAC and replace all the vacuum lines.

01-12-13, 06:54 PM

01-12-13, 07:42 PM
.....You COULD put in a little effort, and find the meanings yourself. There's a sticky right here on these forums:


Or at very least, just ask nicely.

The members here are not getting paid, and are not required to walk you through everything.

01-12-13, 08:01 PM

01-12-13, 09:41 PM
You came to these forums asking for help, which the members here have been providing you. If you don't understand something, fine, ask for an explanation, and you shall receive. .....But:

IAC??? TPS??????

come on guys, what you think we spend are life studying Mech abbreviations^^That^^ post has a bit too much of a snappy attitude to it. How are we to know that you don't know the meanings of the acronyms, AND that you're unwilling to invest a VERY small amount of effort on your part, to simply look up their definitions? We can't read your mind. Just don't expect to get more information than what you ask for, and if you have a question, word it a bit nicer.

Lack basic thinking? Be nicer and help people out? Take a look through my nearly 10,000 posts, then tell me how many "bad comments" I've posted.

If you still want help, use the link I posted to find the acronym definitions. They're all in there.

01-13-13, 12:10 AM
Thank You

01-13-13, 12:13 AM
TPS - ThrottlePosition Sensor

01-18-13, 12:31 PM
I think I Finally found it, at least in mine hope it's the same in yours, I found a Vacuum leak, and repair it, my Idle has stop jumping up and down, am going to drive it a few days to make sure that was it, then I tell you were it was.:yup:

01-19-13, 08:39 AM
well common leak on all cateras coming from secondary injection air pump it self, that located under driver side front bumper, if u start you car and its sounds like some one turn on vacuum cleaner out side, thats your pump got unsealed, its easy fix, new pump cost like $400, fix is like $4!
To fix it u have to take down horn that next to the pump, then pump it self. u will see how rivits (that factory used) snap off. so i used long thin bolts (approx 2in long) with small nuts, its like 6 of them there. i did it like 2 years ago!

01-19-13, 01:28 PM
OK I no longer have my idle jumping, I found the problem by accident, I put my hand under the Idle Control Valve 0280140567
[COLOR="#000000"] and my finger happen to cover a crack which was a vacuum leak, I repace it with one I got on e-bay $40.00 and my idle dosn.t jump anymore, check yours out.102653

01-19-13, 03:12 PM
Cool. But I don't have that valve.... My intake manifold looks different.
Smacas throttle position sensor. I don't have it. If I'm not mistaken its all togather in my throttle body.

01-19-13, 05:20 PM
DO, DO"S, sorry about that, my part name is, Idle Air Control Value, see if you can find out what they did or move it in your year of car.