Engine idle dips extremely low on stop, possible electrical issues

[brosifSmith]

I have looked into the 'idle hunt' issue a lot, and am aware of the tsb regarding this, as well as general issues involving bad idling.

However due to my specific circumstances I think I may have an issue more than what a reflash would fix. (although I am going to try that).

I had issues with my used 2015 BRZ when I had just bought it, it wouldn't start sometimes. and one day, it was dead and would not start even after messing with the battery, fuses, etc.

Apparently something in the starter assembly was effed up. I got warranty work done on it and they replaced the whole engine wiring harness along with the fuses, which fixed the problem.

HOWEVER, now, every time I roll to a stop, if I stay in second gear and let it shift itself to first (AT), it will dip really low, 400-500 rpms and then recover back to 700-800.

This happens if I shift down to 1st as well when coming to a stop but not as much.

Furthermore, I have seen multiple times that while this rather severe idle dip is happening, the DRL's will shut off for a split second at the very lowest point, then turn on once it recovers.
(I've only seen this when I pull up to a gas station or somewhere that has big glass windows and I can see the front of the car from the reflection), They only turn off for about 1/2 a second.

It has never died on me. Can anyone speculate what this problem is indicative of?
My car actually idles extremely well when just sitting, or any other time than when it is coming to a stop.

[humfrz]

Originally Posted by brosifSmith

I have looked into the 'idle hunt' issue a lot, and am aware of the tsb regarding this, as well as general issues involving bad idling.

However due to my specific circumstances I think I may have an issue more than what a reflash would fix. (although I am going to try that).

I had issues with my used 2015 BRZ when I had just bought it, it wouldn't start sometimes. and one day, it was dead and would not start even after messing with the battery, fuses, etc.

Apparently something in the starter assembly was effed up. I got warranty work done on it and they replaced the whole engine wiring harness along with the fuses, which fixed the problem.

HOWEVER, now, every time I roll to a stop, if I stay in second gear and let it shift itself to first (AT), it will dip really low, 400-500 rpms and then recover back to 700-800.

This happens if I shift down to 1st as well when coming to a stop but not as much.

Furthermore, I have seen multiple times that while this rather severe idle dip is happening, the DRL's will shut off for a split second at the very lowest point, then turn on once it recovers.
(I've only seen this when I pull up to a gas station or somewhere that has big glass windows and I can see the front of the car from the reflection), They only turn off for about 1/2 a second.

It has never died on me. Can anyone speculate what this problem is indicative of?
My car actually idles extremely well when just sitting, or any other time than when it is coming to a stop.

Hello brosifSmith and welcome to …...The Forum …….

So, …….. is there a problem ……??

I think maybe you are looking for something to call a problem …..

However, if it bothers you …… I suggest you follow through on your strategy for the AT reflash, that just may make you feel better......


humfrz

[Tcoat]

There is a TSB for the 2015 AT idle drop. It is a simple reflash of the TCM. Just take it into the dealer and point out the attached document and they should fix you right up.

http://www.ft86club.com/forums/attac...1&d=1486956417

[HKz]

Originally Posted by brosifSmith

HOWEVER, now, every time I roll to a stop, if I stay in second gear and let it shift itself to first (AT), it will dip really low, 400-500 rpms and then recover back to 700-800.

this part seems pretty normal to me, it sounds like your RPMs are too low so the trans is rev matching into 1st. I imagine you are in manual mode when this happens? Do you experience any idle issues if you force the trans to go into 1st before the RPMs dip below 1 K?

[brosifSmith]

Originally Posted by HKz

this part seems pretty normal to me, it sounds like your RPMs are too low so the trans is rev matching into 1st. I imagine you are in manual mode when this happens? Do you experience any idle issues if you force the trans to go into 1st before the RPMs dip below 1 K?

Yes and yes. It still happens when I shift down to first. I would assume the TSB would fix it except it's weird that it doesn't happen during actual idle. Only when coming to a stop. even right after coming to a stop and it dips low then comes back up it idles fine after that. I'm just worried it will get to the point where it starts to die when I come to a stop.

[brosifSmith]

Originally Posted by Tcoat

There is a TSB for the 2015 AT idle drop. It is a simple reflash of the TCM. Just take it into the dealer and point out the attached document and they should fix you right up.

http://www.ft86club.com/forums/attac...1&d=1486956417

Thanks for the link. I was having a hard time finding the TSB for autos

[carlovestela]

This always happen to me. At full stop. My rpm will go down to 500-600. Then itll be up to 800-900. You will hear it clearly if you have an exhaust.
I think the TSB is all about when youre in P or N and its fluctuating.

Originally Posted by HKz

this part seems pretty normal to me, it sounds like your RPMs are too low so the trans is rev matching into 1st. I imagine you are in manual mode when this happens? Do you experience any idle issues if you force the trans to go into 1st before the RPMs dip below 1 K?

[brosifSmith]

Originally Posted by carlovestela

This always happen to me. At full stop. My rpm will go down to 500-600. Then itll be up to 800-900. You will hear it clearly if you have an exhaust.
I think the TSB is all about when youre in P or N and its fluctuating.

That's what I'm thinking, but I have a feeling that it would still have an effect on my issue. It's at least worth a try because it bothers me...

[shiumai]

Originally Posted by brosifSmith

HOWEVER, now, every time I roll to a stop, if I stay in second gear and let it shift itself to first (AT), it will dip really low, 400-500 rpms and then recover back to 700-800.

Furthermore, I have seen multiple times that while this rather severe idle dip is happening, the DRL's will shut off for a split second at the very lowest point, then turn on once it recovers.

My car actually idles extremely well when just sitting, or any other time than when it is coming to a stop.

Mine's been doing this since day 1 when I first bought it in 2013. Idles fine, no RPM hunting or fluctuation. Just dips low when stopping and the DRLs will flicker. Figured it was normal and as long as it didn't stall, no biggie.

[reeves]

Originally Posted by shiumai

Mine's been doing this since day 1 when I first bought it in 2013. Idles fine, no RPM hunting or fluctuation. Just dips low when stopping and the DRLs will flicker. Figured it was normal and as long as it didn't stall, no biggie.

Same here since day 1 (manual transmission)

Not only does the idle dip when stopping, but it continues to fluctuate/dip while I'm stopped (in neutral of course). Sometimes it dips low enough to flicker the DRLs, sometimes it doesn't.

I just ignore it. It hasn't left me stranded on the side of the road, that's all that matters.

[carlovestela]

Yeah. Go to dealer. Its free anyway. Then tell us what they did.

Originally Posted by brosifSmith

That's what I'm thinking, but I have a feeling that it would still have an effect on my issue. It's at least worth a try because it bothers me...

[BRZnut]

Me too with auto. Get a dip since day one 6 years ago in my 2013, especially if I come to a rapid stop. Has never stalled.

[N1rve]

I experience the same flickering on my 10 series LED DRLs. I've tried to fix it by replacing my battery but that didn't seem to do it. Never stalled though. Sometimes mines flicker off and on twice when I come to a stop.