RPM Dip - ECU?
 

Hi all,

I know this topic was mentioned in the forums before but I am asking for advice from you all.

I recently purchased a 2013 FRS with 38,000. It currently has 40,451 on the odo. Since owning it, I have experienced a dip in RPM’s from 500-1000 when going into 1st gear/going to neutral. I brought it to the dealership and they said they re-flashed my Ecu and the problem was solved for a few days. Recently, the dip/spike in the rpm’s has returned. I am not sure what to do as the problem keeps recurring. Should I go back to the dealer and get it fixed? Is there anything they can do? Or should I get it re-flashed by a tuner?

Thank you all.

I’ve had a similar issue on my 2015 BRZ. It’s an auto though, but when coming to as stop, it’ll dip down to like 550 or so and then go up. Also, I literally can’t sit in the car with the AC on because it’ll go from like 550 up to 1,100. There are a couple other little issues regarding the RPMs on my car but it’s not so constant that it becomes a serious issue. I’ve been told somethings are normal and I’ve also been told I can take it to the dealership and they’ll fix it. They did it for you for free or no?

Hello frxe and welcome to our friendly, helpful forum - :clap:

I am part of the friendly part, others will come along as part of the helpful part.

I'm not sure what you feel is a "problem", you would you please further explain.

Is your AC running at the time this occurs?

Others will be along soon with some possible explanations/solutions - :)


humfrz

Mine does the same thing dips down to around 500 rpm and I feel like it might cut off. It always recovers but a little unnerving sometimes.


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It’s weird and annoying. I wonder why it happens :iono:

^^^this, including defog/defrost mode

Yep, for you folks with this concern, as eluded to, the change in idle may be the engine responding to the compressor on the AC unit being turned on and off.

humfrz

auto or manual?

my manual does it occasionally, i would understand an automatic doing it while the transmission puts a different load onto the motor to spin up the torque converter.

basically, it's not a problem for me as long as it don't stall.

My car does it as well with the a/c or the defogger going.

i figure if it ever becomes an issue then its time to look at the IACV or do the dirty thing and just set idle to like 700 or 1000....

I had a story about that

*gets my Humrz glasses on*

So way back when I had a 2.5RS and we had done some serious modifications to the head, cam and intake and exhaust on the car, to the point i even had a special throttle body made. Now this was back when throttles had mechanical pulleys in them and return springs. wel my ported throttle body was a different unit and housing than was on the old EJ251 motor ( single slammer. I loved the valve sizes on em) it didnt have an idler control valve

So it became an issue with the ecu, I think we used a vipec V44 which was an off shoot of the Link G4 units. and setting the Idle with the accessories going like ac or defogger or even radio. Since the Throttle body was sort of, what it was we did the old hot rod thing and drilled a hole in it to "mechanically set" the idle.

now with our fancy new drive by wire/sealed units, your computer has an expected idle rpm and indicated and adjusts the throttle to match.
My old S13 had a set screw for a hard throttle stop, but it still had an IACV too. you could mess with it alot.

Anyways we drilled it out and started it up till it got hot and figured to not stall the car out while the ac was going full blast we had assumed a mechanical idle set at like 800 rpm, but we miss judged the hole and shoved a 5/64th bit to set idle, and it gave the car a 1000 rpm idle.

good think she spun up to 7600, but man it was funny sitting at stop lights and literally slipping the clutch cause you couldnt go any lower. Never had an issue with the ac though

I miss that car

Every low displacement 4 cylinder car I ever had did this. Some more noticeable than others but they all did it. Not an "issue".

Good story - :thumbsup:


humfrz

My car as well, driving in mild traffic the other day I kept thinking my car was going to stall. I had the A/C on. The RPM would sometimes dip below 500


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Just an update on my situation. I changed my OFT tune to stage 2 and it seems to have fixed this issue. I’ve heard that a stage 1 tune on a stock car will smooth out the idle, but I don’t know for sure.


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there was nothing to fix like the crickets. if variations in idle speed bothers you guys so much, then I think y'all aren't doing enough actual driving!

OR,..... maybe they need a bigger engine - :iono:

Didn't used to have those problems, back in the day.


humfrz

I raised my idle to 900rpm. No more stumbling, also doesn't dip low if you clutch in from a high rpm and let it drop, it stops right at 900. Even with a/c or defrost at full speed

As much as I love a calm 650rpm idle, this car acts say better at 850-900 for me.

Hell, our old 2 cylinder John Deere tractor would idle quite smoothly at 150 RPMs.

However, it had a 10,000 pound flywheel - :D

https://youtu.be/xcdlgkyE9hc

"You can take the boy off the farm, but you cannot …." something or other - :confused0068:


humfrz

I agree, unfortunately driving in traffic on hot summer Texas days happens sometimes. [emoji28]
And something interesting about the crickets, my FR-S had them when I first bought the car. They’ve been gone after I started filling up with 93 octane at Valero. *shrug* [emoji848][emoji3074][emoji3074][emoji3074]


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Mine got pretty shaky once during a 90 degree day when I was stuck at a light for almost 15 minutes in city traffic. I don't recall what the RPMs were doing, but the temp gauge read normal so I couldn't figure out why it was shuttering. I turned the AC off and opened the windows. Car was happy, I suffered.

I remember my old Corolla XRS doing an RPM dip when stopped when the AC was on. There was also a clear drop in power too when the AC was on.

More recently however, my Scion IM is doing it.

At times I stop at a light and I can feel the car (and see the RPM) fluctuate between around 500ish to 1000rpm when stopped (leveling off at 750ish for a period before it does it again).

I figured it had something to do with the A/C compressor due to previous experience but I don't have defog or anything that I would think would activate the AC compressor...….so I thought it was weird.

I did have an oil change and that SEEMED to have fixed it for like a week or two but then it came back.

Ill live with it, but I don't know why the car fluctuates the idle as much as it does.

My car would do the RPM dip to the point of almost dying as well, after flashing to OFT Stage 1 it cleaned it up and hasn't done it since. Now I just gotta get my header on so I can flash stage 2... :burnrubber:

I have ECUTEK and I was able to get Mike to add in some padding when the throttle closed with the A/C on. Now it kind of hesitates before dropping to idle. It works quite nicely.

Worst ecu, EVER.

Got me. Spit my food a little.

Seriously, I know a bunch of local owners, driven many, worked on many...

Not once have I seen one that dipped or shuddered like described here. There's a little bit of it coming from unanticipated changes to accessory load but nothing dramatic. :iono:

Just for the record, I don’t drive my car I just rub it with a diaper



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nice! the tradeoff is you'll most likely avoid a spun bearing, never have to deal with the torque dip and you won't have to change out those pesky poorly designed brakes!