engine revving while i'm stopped... what's going on?
 

hey guys, so last night i was trying to make my way over to HIN in san jose and i noticed a weird behavior with my car. i'm not sure it's a problem, but it did feel pretty strange.

i was in a parking garage, looking for a spot, so lots of stop and go driving. when i'd push on the brake to come to a complete stop, i could feel the engine "revving" a bit, like it was fighting my braking. here's the weird thing, i'd look at the tach, and the rpms would just stay @ 800 or 1000. i could feel some vibration in the brake pedal. if i took my foot off the brake, i could see the rpms slowly increase from 800 to over 1000 without me applying any gas. when i was at a full stop with the brake applied, i could hear the engine working louder than usual and my friend who was with me said she could hear it too.

i'm not sure what to make of it. it could be that this is somewhat typical and i'm not used to it (i had the AC on, which i don't usually turn on).

should i take this issue to the dealer and get it checked out?

Did you accidently push the gas and the brake at the same time? I sometiems accidently touch the edge of the gas pedal when i brake hard

i thought that might be happening so i was careful to make sure i wasn't pushing them both @ the same time when i observed this problem. that's a good point tho.

With the A/C on, engine revs higher so it won't stall.

Next time it happens, turn a/c off to see if the idle comes down to normal.
C.

I get the same thing happening every now and then... I thought it might be because I'm on the brake and throttle as well, but it's still revving when I have both feet in the air... feels like the throttle gets stuck at times...


If you're sitting still and your idle is just going up down, then you have a vacuum leak somewhere. That might be my problem too...

thanks for the tips guys. i just went for a 20-30 minute spin and didn't have the problem reproduced with that A/C on. i'll just have to keep my eyes open for it. i hope it's not the vaccum leak

This is probably a vacume leak in your brake booster. Seen it before in older cars where there was a problem with the vacume assist. Whenever the breaks were applied a small vacume leak would develop and the idle would increase. If I were you I'd have the dealership check/repair/replace your brake booster.

my dad's i30 used to do that in the winter - infiniti said it was somethign w/ the a/c and normla.

Well the idle is bumped by the ECU both when it is cold and when the A/C is on - and that is normal. However if the problem occurs when you push the brake pedal (irregardless of A/C) then it is probably the brake booster with a leak. I've seen it so bad that you can actually hear the hissing from the leak when the breaks are pushed.

It could be just my experiences but it seems like the delerships more often than not say it is "normal" when they don't have a solution/explanation for the problem. Sometimes I think they don't know their a$$ from a hole in the ground.

shunra: thanks for the info! i'm going to see if it keeps happening, if it does, i'll definitely take it in and have them check that out

Well I don't think it was a leak - this last happened over a year ago and hasn't since.