Is this normal? rpm drop when hard braking

[szjalo]

tried to search but did not find any answer. I have just bought a 2014 scion FR-S (AT) with 29k miles on. I have noticed recently whenever I stop the car after hard brakes, the rpm will drop to 500 or sometimes a little lower, then bounce back to 6-700. No CEL, no shaking, idle is quite smooth and stable at 700, not that common fluctuation issue in this forum. and this rpm dip only happens at hard brakes (meaning if I slowly stop the car without aggressive brake, the rpm stays at 600-700), or stop the car on uneven surface (uphill and etc.)

look forward to your insights

[Rakshaa]

Hi @szjalo and welcome to the forum! Congratulations on your 2014 FR-S purchase, you're going to love the car!

I also have a 2014 and this is very common. You'll find there are lots of other little quirks to this car that would appear to be abnormal but are totally fine (creaks and squeaks, the 'crickets' underneath the hood etc.)

My best guess is the engine just regulating itself after a quick drop in RPM from hard braking. I have just passed over 100k kms in mine and no issues (knock on wood) and its been doing this from pretty much day 1.

Edit: Come to think of it, not sure mine dips below 500 though...sorry, just read that detail there, so I'll see what other owners have to say.

[humfrz]

It's just "flinching" thinking you're about to hit something......

I can't help, cause I don't have an AT ...... but, if the engine doesn't die or shudder, I wouldn't worry about it.

There also is a TSB that pertains to early model cars with AT and idle issues, you may wish to look into.

@Tcoat may find it for you in the morning ...... I'm too tired tonight ...... all-day day care with all three granddaughters about wore me out.......


humfrz

[WorldRallyB]

Originally Posted by szjalo

tried to search but did not find any answer. I have just bought a 2014 scion FR-S (AT) with 29k miles on. I have noticed recently whenever I stop the car after hard brakes, the rpm will drop to 500 or sometimes a little lower, then bounce back to 6-700. No CEL, no shaking, idle is quite smooth and stable at 700, not that common fluctuation issue in this forum. and this rpm dip only happens at hard brakes (meaning if I slowly stop the car without aggressive brake, the rpm stays at 600-700), or stop the car on uneven surface (uphill and etc.)

look forward to your insights

While not on my BRZ i had similar RPM dips issues on another vehicle. In my case it was a dying battery. Go get yours tested, also make sure that heavy SOB has clean terminals with no corrosion and its secured properly. 3 years 30k miles? You might be due

[Da Brz]

It's normal for the car.

It's not something that I'm okay with, but it's normal for the car.

My car drops idle after quick stops in neutral and it will also drop idle periodically when sitting still once the weather gets above 60°F.

I put my OBDII reader on it and my average idle RPM is 710. When it drops, it hits about 400-450.

Again, I'm not really okay with that but it seems to be normal. I've got about 22,500 miles on my 2016 BRZ and even though it sure SOUNDS like it's going to die sometimes, it hasn't done it.

[sato]

Yup, it's normal it seems. If you have an auto, then I guess it's not transmission related as that has been one of my complaints on my manual transmission FR-S.

[Tcoat]

Yep normal. Welcome to the wonderful world of low displacement, high compression and higher revving 4 cylinder engines. When you build power through revs instead of displacement you will see a broader range of RPMs since small things have a bigger impact. High revs to a sudden stop, A/C kicking in and out, even just putting a sudden electrical load on them will make the revs drop for a second. It is not an issue and my best advice is to stop looking at the tach all the time.

[kazerotor]

I bought a 2014 FR-S (AT) 1 week ago and this happens to me too. I was concerned about it..but i just baby the breaks a bit more in traffic. Seems like it goes away at some point. I haven't really looked into it any further as the car hasn't died.
Wish my car was (MT) but they only had an (AT) within my budget

[Tcoat]

Originally Posted by kazerotor

I bought a 2014 FR-S (AT) 1 week ago and this happens to me too. I was concerned about it..but i just baby the breaks a bit more in traffic. Seems like it goes away at some point. I haven't really looked into it any further as the car hasn't died.
Wish my car was (MT) but they only had an (AT) within my budget

Mine is MT and does the same thing. Not a problem and no need to baby it.

[Da Brz]

Originally Posted by Tcoat

my best advice is to stop looking at the tach all the time.

In this guy's defense, if it's as bad as mine is, there's no NOT noticing it. The tach could be removed entirely and I'd still feel it shake the car and hear the engine knock through the dash.

[Tcoat]

Originally Posted by Da Brz

In this guy's defense, if it's as bad as mine is, there's no NOT noticing it. The tach could be removed entirely and I'd still feel it shake the car and hear the engine knock through the dash.

Oh I would get that checked. Mine drops but there is no shaking or knocking involved. It just dips down for a second and comes right back up. Hardly even notice it.

[BRZnut]

Mine has done this since day one...2013 BRZ Auto...with hard braking. Less so with a gradual stop. Has never stalled and quickly recovers. Still does it today at 35K miles. So as others have stated...normal for this car!