Chugging idle

[alpinee30m50]

The idle on the m50 is more or less fine when im off the brakes, but when im on the brakes sitting at a stop light it chugs, sits at about 600 rpms and sounds like its got a cam with everest sized lobes, but then when i get off the brakes to go to gas its fine again. Is this a bad brake booster or could it be anything else?

[Suspence]

I'm guessing it could be your MAF hose. Mine has a crack in it and I'm replacing it tomorrow or Tuesday. When I sit at stop lights it idle's pretty hard, but once I get going it's fine.

[dranttna]

while idleing hold the brake down and spray some brake cleaner or starting fluid on the atmospheric port on the booster (were pedal attaches). if it raises the idle you have a bad booster diagram.

[NC325iC]

while idleing hold the brake down and spray some brake cleaner or starting fluid on the atmospheric port on the booster (were pedal attaches). if it raises the idle you have a bad booster diagram.

stretch armstrong?

[ZombiE30]

you will need an assistant for the test as described, though i'm pretty certain that if it's a vacuum leak (probably is) it should be there whether or not you're on the brakes.

also, i believe he meant 'diaphragm' not 'diagram'.

If you conduct the above test and the idle changes it could just be the junction where the hose connects is loose/cracked (aka vacuum leak).

edit: if you're having difficulty applying the brakes, (ie it feels like trying to brake when the engine is off) THEN you have a bad diaphragm. If brake pedal operates as normal, the diaphragm is fine.

[alpinee30m50]

Yeah the pedal feels a bit weird, but its not hard to apply the brakes or anything and it idles fine with the brakes off. When i take the brakes off and then slam them on the idle goes down almost to where the car dies, then it comes back up to idle. Ill do the test tomorrow just for shits and giggles