RPM fluctuation.....

[Futaba]

Mine occasionally dips to around 400, car gets wobbly for a second until the ECU cottons on and boosts rpm to compensate, sometimes in time with the AC compressor, sometimes the radiator fans, sometimes for no real reason at all, I've learned not to panic about it, if it isn't stalling it isn't a big deal to me.

I find it happens less if I let off the clutch in neutral and haven't just come to a complete stop after gunning it, my guess would be the fluctuations are down to the heavy gas usage suddenly swapping to idle and the fuel miz being off a little.

Has anyone that has this issue WITHOUT CEL kicking in actually had the car stall on a 2014 or newer car? I doubt it.

Last but not least stick to the same fuel, don't be putting in regular then randomly premium because you're making it hard for the ECU to nail down a good setting!

[ninedice]

This used to happen to me. I took it to the dealership and they did some TSB on the ecu and told me it was better. Kept happening so I bought an openflash tablet and changed my idle to 1000. It hasn't shuddered since.

[Tcoat]

Originally Posted by Futaba

Mine occasionally dips to around 400, car gets wobbly for a second until the ECU cottons on and boosts rpm to compensate, sometimes in time with the AC compressor, sometimes the radiator fans, sometimes for no real reason at all, I've learned not to panic about it, if it isn't stalling it isn't a big deal to me.

I find it happens less if I let off the clutch in neutral and haven't just come to a complete stop after gunning it, my guess would be the fluctuations are down to the heavy gas usage suddenly swapping to idle and the fuel miz being off a little.

Has anyone that has this issue WITHOUT CEL kicking in actually had the car stall on a 2014 or newer car? I doubt it.

Last but not least stick to the same fuel, don't be putting in regular then randomly premium because you're making it hard for the ECU to nail down a good setting!

I am with you on this. I have had it happen twice. Both times after a long highway run and then into stop and go traffic. The ECU took a couple of minutes to figure things out. It went away and I never worried about it.

[steve99]

Originally Posted by ninedice

This used to happen to me. I took it to the dealership and they did some TSB on the ecu and told me it was better. Kept happening so I bought an openflash tablet and changed my idle to 1000. It hasn't shuddered since.

Originally Posted by Futaba

Mine occasionally dips to around 400, car gets wobbly for a second until the ECU cottons on and boosts rpm to compensate, sometimes in time with the AC compressor, sometimes the radiator fans, sometimes for no real reason at all, I've learned not to panic about it, if it isn't stalling it isn't a big deal to me.

I find it happens less if I let off the clutch in neutral and haven't just come to a complete stop after gunning it, my guess would be the fluctuations are down to the heavy gas usage suddenly swapping to idle and the fuel miz being off a little.

Has anyone that has this issue WITHOUT CEL kicking in actually had the car stall on a 2014 or newer car? I doubt it.

Last but not least stick to the same fuel, don't be putting in regular then randomly premium because you're making it hard for the ECU to nail down a good setting!

Originally Posted by Tcoat

I am with you on this. I have had it happen twice. Both times after a long highway run and then into stop and go traffic. The ECU took a couple of minutes to figure things out. It went away and I never worried about it.

If you have access to ecu tables zero out the Port/direct injection ratio tables up to 0.2 engine load for manual and 0.3 if you auto like below.

Their are three tables cold/warm/hot do all three.

This will make ecu run full Direct injection at idle and its not trying to inject very small amounts of fuel via both injection systems, works well

bump the idle to 700 or 750 from the stock 650

[Newtothegrounds]

Originally Posted by steve99

are you on good fuel ?
if fuel is ok take it to dealer, maybe video issue to show them if its intermittent.

I usually always fill up at the esso by my house I use 91 Oct as I don't think there is any higher in Ontario Canada , at least not that I've seen. I do live on the border with the states I know the pumps there go to 97 I think, haven't tried filling it there yet.

[Scavanger]

So it is the forward o2 sensor for now (that's what they think anyway) which is what I told them from the begging that I thought it was the o2 sensor but its all good should be getting a new one in soon and we will see if the issue goes away

[Ultramaroon]

Originally Posted by Futaba

Mine occasionally dips to around 400, car gets wobbly for a second until the ECU cottons on and boosts rpm to compensate, sometimes in time with the AC compressor, sometimes the radiator fans, sometimes for no real reason at all, I've learned not to panic about it, if it isn't stalling it isn't a big deal to me.

I find it happens less if I let off the clutch in neutral and haven't just come to a complete stop after gunning it, my guess would be the fluctuations are down to the heavy gas usage suddenly swapping to idle and the fuel miz being off a little.

Has anyone that has this issue WITHOUT CEL kicking in actually had the car stall on a 2014 or newer car? I doubt it.

Last but not least stick to the same fuel, don't be putting in regular then randomly premium because you're making it hard for the ECU to nail down a good setting!

Originally Posted by Tcoat

I am with you on this. I have had it happen twice. Both times after a long highway run and then into stop and go traffic. The ECU took a couple of minutes to figure things out. It went away and I never worried about it.

I'll pile on here. It dips for me occasionally but, meh. I do a ridiculous amount of stop-&-go. One day for some reason, it just started idling high at around 1K. I'd go for a couple hundred feet and stop. The RPM would drop to normal and then climb high again. As soon as I got onto some open road for a few miles it settled down.

[arvidj]

I would like to thank the experts on this forum who provided well reasoned comments on the the issue ...

Originally Posted by Koa

Jesus guys, it's the damn accessories kicking in. How hard is this to understand? Stop being paranoid!

Originally Posted by fatalelement

Thank you for being one of the only other lucid people here. I read threads all day about this bullshit. my Camry did it too. It's your ac and all the other dumb shit your car needs on that has to draw power and can only run for a bit at idle rpm before your car kicks it up to keep it alive.

Have you guys driven literally any other car? I have never been in an affordable (<=25k ) car that didn't do this in idle with accessories on.

Originally Posted by Koa

Steve hit it on the head. It's not a big deal in other words. Your 50 years of automotive experience is nullified by the vast changes in car ECU architecture and implementation. Do you realize that it's above and beyond just simple mechanisms and that our idle is controlled by a complex ECU? Have you ever worked with and tuned Renesas style ECUs? Are you worried there's some mystery leak or misalignment, or your engine is simply 'different'?

Have you tried tuning? Did you get the TSB flash updates- which, by the way, were served because of people stalling and bucking under certain conditions, not just NORMAL RPM fluctuation. Are you truly worried there's something 'wrong' with your vehicle to the point of being that butthurt about it?

I said accessories, but I should have worded it as thus: "DON'T WORRY ABOUT IT"

Originally Posted by Koa

You're creating a problem in your own head by saying the vehicle does not idle "correctly". What is incorrect about this? Surely with 50 years of automotive experience you can tell us how this is hurting our engines and is not "correct" for the car's stock configuration?

Sorry but as soon as you started throwing around your 50 years of auto experience it opens you up to critique

I will leave with a valuable, relevant piece of perspective that may explain why I feel the need to contest your stance on the ordeal:

"Learning over knowing"

I am anxious to learn how this "idle hunting" behavior is adverse to our engines, trust me I want to know!

Originally Posted by Tcoat

Where to start?
The first 30 years worth of cars do not mean shit in this case! Mechanical advanced timing and adjusted carburetors did not have the fine responses the electronically controlled engines do (come on you know that).


The 73 Pontiacs were sadly lacking in computer controlled systems of I have been very wrong in how I worked on my cars.


Great, you drove a bunch of cars but I do not see any Subarus on that list. After "50 years" of owning cars I would think you know that different makes can have different traits.


You want something to be wrong sooooo badly that when the dealer and several very knowledgeable people tell you that the situation is normal you throw out your 50 year of expertise as your only answer? That is the kind of shit that makes the older guys look bad on here!
If you are so sure it is wrong take it to another dealership or shop and get a second opinion and then another, and another. If you just keep fishing you find somebody that agrees with you

Originally Posted by Tcoat

None! It was an early model problem that was fixed. If you read all of the posts you will see that other then a couple of people that expect a rock solid idle from a boxer engine all the vehicles were early 13s.
The idle does go up and down but it is a normal function of a very precisely computer controlled system.
If it is dropping so far that you are stalling then you may have a problem that requires service but otherwise don't worry it is perfectly normal.

On the other hand, those of you who are experiencing this "not really happening, not an issue, it's all in your mind, it's normal" issue please visit your Scion dealer and ask them to review ...

Technical Bulletin S-SB-0021-15, issued September 17, 2015, Idle Fluctuation in Park or Neutral.

Applicability: 2015-2016 FR-S

Introduction: Some 2015-2016 model year FR-S vehicles may exhibit a condition where the engine idle speed fluctuates (typically 500 - 1000 RPM) only when the transmission is in the Park or Neutral shift position. This condition occurs after the vehicle has been driven about 25 miles or more at highway speeds. The Transmission Control Module (TCM) logic has been revised to address this condition.

I had the TCM software upgraded yesterday ... about an hour at the dealer total time ... and the idle is now rock solid.

[Tcoat]

Originally Posted by arvidj

I would like to thank the experts on this forum who provided well reasoned comments on the the issue ...

On the other hand, those of you who are experiencing this "not really happening, not an issue, it's all in your mind, it's normal" issue please visit your Scion dealer and ask them to review ...

Technical Bulletin S-SB-0021-15, issued September 17, 2015, Idle Fluctuation in Park or Neutral.

Applicability: 2015-2016 FR-S

Introduction: Some 2015-2016 model year FR-S vehicles may exhibit a condition where the engine idle speed fluctuates (typically 500 - 1000 RPM) only when the transmission is in the Park or Neutral shift position. This condition occurs after the vehicle has been driven about 25 miles or more at highway speeds. The Transmission Control Module (TCM) logic has been revised to address this condition.

I had the TCM software upgraded yesterday ... about an hour at the dealer total time ... and the idle is now rock solid.

Thanks for the update! As said many times this is not the same issue the 13s had.
In fairness to those that said that it was "normal" etc that was the information available from the dealers at the point in time that the comments were made. Since there is a new TSB issued those comments will no longer be accurate.
We need to get our hands on a copy of the TSB to place in the stickyed thread.

[fatalelement]

Originally Posted by arvidj

I would like to thank the experts on this forum who provided well reasoned comments on the the issue ...

I had the TCM software upgraded yesterday ... about an hour at the dealer total time ... and the idle is now rock solid.

haha well I would like to offer my sincere apologies! thanks for spearheading this. Mine stopped when I tuned it for a lower fixed idle, but I may ask the dealer to take a look at the TCM if I go in anytime soon.

sorry for being a ****! haha it looks like I was having a rough day

[cdo221]

Originally Posted by arvidj

Technical Bulletin S-SB-0021-15, issued September 17, 2015, Idle Fluctuation in Park or Neutral.

Applicability: 2015-2016 FR-S

Introduction: Some 2015-2016 model year FR-S vehicles may exhibit a condition where the engine idle speed fluctuates (typically 500 - 1000 RPM) only when the transmission is in the Park or Neutral shift position. This condition occurs after the vehicle has been driven about 25 miles or more at highway speeds. The Transmission Control Module (TCM) logic has been revised to address this condition.

I had the TCM software upgraded yesterday ... about an hour at the dealer total time ... and the idle is now rock solid.

THANK YOU so much for this, gonna bring it in to my dealer again with this. They said they didn't notice any issues when I brought it in and I just let it drop since it wasn't really affect use of the car.

[Premium 615]

Great update! Thanks for sharing.

[Ultramaroon]

Originally Posted by arvidj

Some 2015-2016 model year FR-S vehicles may exhibit a condition where the engine idle speed fluctuates (typically 500 - 1000 RPM) only when the transmission is in the Park or Neutral shift position. This condition occurs after the vehicle has been driven about 25 miles or more at highway speeds. The Transmission Control Module (TCM) logic has been revised to address this condition.

This was my second guess.

[AsianStyle]

So, this new TSB only affects 2015-2016 models? What did they change from the 2013-2014 that the old fixes don't work for them?

Seems odd to have a new fix on an old issue for a newer subset of cars, when they haven't changed anything to the engine.