RPMs drop when pressing the brake pedal

[larryw240]

Hey guys,

I had an issue with my car, and I was wondering if someone could help me out. My car starts up and holds a normal idle, but I realized that when I press the brake pedal the RPMs drop. Once I let off the brakes, the car returns to a normal idle.

I wouldn't look at this as much of a problem, except that it gets worse when I'm coming to a rolling stop, while clutching in and braking at the same time. RPMs drop to 400-500rpm, steering gets heavy, and the car feels like it wants to stall. Also, even when I'm parked and I press on the brakes just enough so that the brake lights come on, the RPMs will drop about 100rpms.

I've done a lot of research and replaced/cleaned a bunch of things: IACV, brake booster check valve, Ignitor coil, rotor and cap, spark plugs and wire.

Anyone can give me anymore insight into what I should try next? My engine grounds are pretty dirty so I was gonna try clean them up next.

Any help is appreciated!

[djrice123]

Vaccum leak. Find where. Had it on my old 240sx, same deal. To resolve I would just have the A/C or heater on all the time as it brings the RPM idle up to 1000RPM and as well I would blip the throttle when it was about to stall. Never did figure it out, so I just sold the 240.

Maybe brake booster as well?

Common problemon 240

[pacotaco345]

Check all the grounds to your brakelights, the lights are putting too much draw on the alternator. I used to have this problem, I forgot which ground it was but I cleaned a shit ton of them and it eventually fixed it.