MX-3.com

Also, here is a video I took of the tachometer, http://www.youtube.com/watch?v=boizEtuAeh0

When the video begins, my foot is on the brake. I take my foot off the brake and the rev goes up like 200-300RPMs then i push the brake peddle down and the idle drops. It is only happening now whenever I do this brake action.

what is your idle at with the car warmed up and not in gear? my 92 gs would always raise the idle once the car is in gear with the clutch down. if its set too high in the first place it will cause it to jump like your describing. idle should be around 600-700rpm

yeah idle sits at about 700RPM without in gear

you must have a vacuum leak somewhere. its not too expensive to replace all your vacuum hoses, id give that a try and go from there...

I went out and even sprayed Carb Cleaner on stuff and no change in idle and listened for any leaks and looked at hoses and can't identify any leaks. It doesn't help the manual page for the hose diagram for vac is extremely compact and barely can make out what hose is where.

try wiggling the hoses when you spray carb cleaner. your not getting any codes eh?

oh im assuming that video is with your engine cold? the clutch/brake system will have an effect on idle, shouldnt be that much thow. only time ive had the idle jump like that with the brake is when the motors cold.

Nah I didn't wiggle any of the hoses but should of, maybe ill try it later. Nope, no codes either (i wish so it'd make this easier lol). I was just thinking if it was a vac issue wouldn't it cause rough idle and wouldn't be so specific? could this be something with my brakes? I just dont get why it does it when brake is pressed down, could that cap being cracked (the brake fluid filler cap) be leaking pressure although I feel no difference in my brake pedal?

EDIT:: the video was when the engine was up to mid heat (between Cold and Hot where it should be)

I found a bad vac leak in the vac chambers and one-way check valve and have replaced all the parts and the freaking car still SURGES. I can't freaking believe this crap, I'm so close to just selling this car though. It definitely CAN'T be a vac leak i dont think. Could this be IAC related? How do i test?

Also, I checked the ohm reading on my IAC valve and got only 2-3 ohms, and the book stats it needs to be like 10.7-12.3 (when car is at 68F) but my car wasn't fully cooled down, does that matter?

Aaaaaaannnnnddd (lol) would the IAC valve from a probe's V6 engine fit the exact some on my throttle body or should I yank the entire TB?

Hopefully you haven't already posted the for sale sign. The IAC in our car should not be affected by the brake. The IAC only allows extra air past the throttle at idle when the engine is cold. If you have a good fast cold idle that eventually settles to 700 rpm when warmed up then your IAC is OK.

I watched the video and also think you have a vacuum leak related to the brakes. The brake booster relies on vacuum from the intake manifold.
How does the rubber hose from the intake manifold to the booster look?
Has the effort to press the brake pedal changed? If the brake pedal is harder to press - stiff almost immediately then your brake booster may have a leak.

I fixed the issue, the one-way check valve hosing that goes into the vac chambers under the intake manifold was broken and also one of the vac chambers plastic pieces broke. Pulled two vac chambers and a one way check valve off a Probe and now my MX-3 is in working condition.