the rev dipping issue

[Tcoat]

Originally Posted by Mwillywag

I realize this is a very old thread, but I have a 2015 Scion - FRS (13,000 mi.) and am experiencing an idle problem. If I drive the car on the freeway (60 - 65 mph) for around 30 miles, when I come to a stop, the engine idle drops to around 500 rpm, jumps back to around 900 rpm, then slowly drops and repeats the cycle about every 30 seconds or so. No engine light. It does not always happen and it occurs in the summer and the MN winter, does not matter the outside temperature or raining/snowing/or dry. I did notice that if I shut the engine off and wait at least 10 seconds, start the engine back up, the idle returns to normal.
I will be going to the dealer today for a key interlock recall and oil change and will mention it to them to see what they say. I took a video of the issue to show them. I read that a re-flash of the ECU was recommended, but reading posts indicated this could have been resolved already.
Wish me luck.

There is a TSB for that in the autos: http://www.ft86club.com/forums/attac...1&d=1443640063

[FR-Sky]

I am having that problem as well.. only when AC on tho.
I remember OFT can fix this problem? correct me if i am wrong.

[Tcoat]

Originally Posted by FR-Sky

I am having that problem as well.. only when AC on tho.
I remember OFT can fix this problem? correct me if i am wrong.

When the AC is on or even the heat when on the defrost setting the car will dip. This is a normal thing as the compressor cuts in and out and happened on all cars to some extent. The small displacement of the FRS/BRZ engine in combination with the lack of sound proofing just makes it that much more noticeable. It is not a problem in any way.
OFT can probably turn off the dry cycle when on heat and defrost but it will have no impact when the AC is on since it is just the sudden draw of the compressor that is causing the drop.

[KendallH]

Originally Posted by Tcoat

When the AC is on or even the heat when on the defrost setting the car will dip. This is a normal thing as the compressor cuts in and out and happened on all cars to some extent. The small displacement of the FRS/BRZ engine in combination with the lack of sound proofing just makes it that much more noticeable. It is not a problem in any way.
OFT can probably turn off the dry cycle when on heat and defrost but it will have no impact when the AC is on since it is just the sudden draw of the compressor that is causing the drop.

Tcoat, I see where your logic is at, but in the case of the twins there is an actual problem concerning idle drop. The idle drop in my personal vehicle is so noticeable I actually see a slight dimming of my lights and feel a decent vibration when the idle dips down to 450-500 RPM. Modern vehicles using electronic throttle and closed loop fuel injection can very quickly and effectively increase idle speed to negate this effect, however the FRS and BRZ do in fact suffer from an abnormal idle dip during a stopped situation.

[Tcoat]

Originally Posted by KendallH

Tcoat, I see where your logic is at, but in the case of the twins there is an actual problem concerning idle drop. The idle drop in my personal vehicle is so noticeable I actually see a slight dimming of my lights and feel a decent vibration when the idle dips down to 450-500 RPM. Modern vehicles using electronic throttle and closed loop fuel injection can very quickly and effectively increase idle speed to negate this effect, however the FRS and BRZ do in fact suffer from an abnormal idle dip during a stopped situation.

Yes some do especially ATs which is why I linked the TSB for that problem. My comment there was in reply to those that were mentioning the drop due to the AC cycling. It is not the same thing.
Mine has had the idle drop twice when coming in off a long run on the highway. Considering I do a long run on the highway 5 days a week and have for the last 1 1/2 years I am not worried about it.

[krayzie]

Originally Posted by KendallH

Tcoat, I see where your logic is at, but in the case of the twins there is an actual problem concerning idle drop. The idle drop in my personal vehicle is so noticeable I actually see a slight dimming of my lights and feel a decent vibration when the idle dips down to 450-500 RPM. Modern vehicles using electronic throttle and closed loop fuel injection can very quickly and effectively increase idle speed to negate this effect, however the FRS and BRZ do in fact suffer from an abnormal idle dip during a stopped situation.

I went for a test drive of the manual FRS when they first came out, me and my friend did see this issue while waiting at the intersection exactly like you described. We saw the shifter vibrating like mad and the A/C was on. We thought it was because of an abused demo car.

However my 2014 manual BRZ made in Summer 2013 has never done this even with the A/C on.

[Tcoat]

Originally Posted by krayzie

I went for a test drive of the manual FRS when they first came out, me and my friend did see this issue while waiting at the intersection exactly like you described. We saw the shifter vibrating like mad and the A/C was on. We thought it was because of an abused demo car.

However my 2014 manual BRZ made in Summer 2013 has never done this even with the A/C on.

I do get the brief drop when the AC kicks in but it is not dramatic. They did seem to iron the severe drop out from the 14s up but there are still a few that say they get it.

[FRSBRZGT86FAN]

Originally Posted by krayzie

I went for a test drive of the manual FRS when they first came out, me and my friend did see this issue while waiting at the intersection exactly like you described. We saw the shifter vibrating like mad and the A/C was on. We thought it was because of an abused demo car.

However my 2014 manual BRZ made in Summer 2013 has never done this even with the A/C on.

Originally Posted by Tcoat

I do get the brief drop when the AC kicks in but it is not dramatic. They did seem to iron the severe drop out from the 14s up but there are still a few that say they get it.

There was actually an idle fix ecu flash for 2013s and of course applied in production for future models that's why it's not as crazy as before.

[Teseo]

I got the reflash at dealer and still have the dip. I gave up and add it to the quirks list. Considering the oft tought.

[RichardsFRS]

Mine does it, everyone's does it, but shouldn't. I'm gona see if toyota will re-flash mine when I take it in for next service

[steve99]

Originally Posted by Tcoat

When the AC is on or even the heat when on the defrost setting the car will dip. This is a normal thing as the compressor cuts in and out and happened on all cars to some extent. The small displacement of the FRS/BRZ engine in combination with the lack of sound proofing just makes it that much more noticeable. It is not a problem in any way.
OFT can probably turn off the dry cycle when on heat and defrost but it will have no impact when the AC is on since it is just the sudden draw of the compressor that is causing the drop.

yep the 2015 auto need the auto controll unit reflash

oft tunes just bump the idle 50 or 100 rpm above stock.

better fix is to adjust the idle compensation tables

[sly]

I have a 2016 Limited manual with a Cosworth 1.0 EcuTek tune. Mine does it too when the A/C compressor is on. If I come off the highway and shift into neutral, the idle will drop to about 500rpm and shudder a little. It doesn't do it very much when standing still and doesn't do it all if the A/C is not running.

So I don't believe it's just a tune issue although it's possible that Cosworth did not compensate for it. Maybe it can still be tuned out.

I wonder if @Matt@Cosworth has noticed this on any other Cosworth vehicles. Is the problem in ECU tuning or is it a mechanical issue? Maybe the little 2.0 is just not strong enough to quickly compensate for the A/C compressor cycling.

[Tcoat]

Originally Posted by sly

Maybe the little 2.0 is just not strong enough to quickly compensate for the A/C compressor cycling.

BINGO!
All 3 of my Lancers would struggle like hell when the compressor kicked in since the small displacement takes a second to catch the dip. These engines make all their power through revs so when a load is suddenly placed on them at low RPM they need to catch up.

[Matt@Cosworth]

Originally Posted by sly

I have a 2016 Limited manual with a Cosworth 1.0 EcuTek tune. Mine does it too when the A/C compressor is on. If I come off the highway and shift into neutral, the idle will drop to about 500rpm and shudder a little. It doesn't do it very much when standing still and doesn't do it all if the A/C is not running.

So I don't believe it's just a tune issue although it's possible that Cosworth did not compensate for it. Maybe it can still be tuned out.

I wonder if @Matt@Cosworth has noticed this on any other Cosworth vehicles. Is the problem in ECU tuning or is it a mechanical issue? Maybe the little 2.0 is just not strong enough to quickly compensate for the A/C compressor cycling.

the idle speed on these cars can be a bit erratic
on the stage 1 tune all the stock idle speed control was carried across so its the same as the standard car in this respect and I've found it will improve after flashing once its done about 200 miles as it applies the learned settings