Vaccum leak or what, Help an Mxer out,

[boniclyd]

Hey there Mxer's I need some help,
I have a 94 Mx-3 4cyl DOHC B6
When I depress the brakes (no matter if it is to stop the car or just pressing them while in neutral)
the engine surges, also once I'm at idle, after a second or two the rpm drop down to about 400
or less. If I pump the brakes the RPM will actually restore to about 800. I guessing a vaccum leak.
If you could give me some advice about how to find the leak, or have any suggestions about the cause and repair, please help an Mxer out.



Thanks

[Bumpysbro]

well u can use soapy water and spray on the lines and see if it sucks it in or starts bubbling. you can use a spray bottle or if your really crazy carb cleaner and see when the engine surges. most likely its a vacuum leak but check your brake hose going to your booster. good luck finding it

[umcamara]

well u can use soapy water and spray on the lines and see if it sucks it in or starts bubbling. you can use a spray bottle or if your really crazy carb cleaner and see when the engine surges. most likely its a vacuum leak but check your brake hose going to your booster. good luck finding it

Why do you say use carb cleaner if you're really crazy? Just curious. I've heard that throttlebody cleaner is better for your engine than carb cleaner for this purpose. Is that the context that you meant that in?

[Bumpysbro]

haha ya i just worded it wrong, i have heard from my teacher at the shop that with the engine at operating temp he had a fire spraying carb cleaner on a exhaust pipe. i just didnt want him spraying it everywhere you know.

[umcamara]

Another cause could be a defective IAC valve. The purpose of this valve, other than acting as a choke, is to electronically increase the air through the throttlebody when electrical loads and whatnot are placed on the engine. Using the brakes puts a strain on the engine (brake lights, etc.)

[sexymx3]

I had this same problem, clean the throttle body and be sure that the alternator belts are tight. My car did this for about 2 months and the alternator would go, I'd get a new one and it would run good for a couple of days and then it would begin to idle around 400 when I would press on the brake. Couldn't find any vaccum leaks though..Come to find out from another mx-3 owner, the belts were never tightened enough...Hope this helps