2015 BRZ Idle Hunitng
 

Hi Guys, I was hoping someone might be able to help with my problem.

I have a 2015 BRZ limited automatic that is only 3 months old and has been at the dealership for 3 weeks now and they have no idea what is causing it. The car drives fine, but after the engine gets hot and I put in park or neutral the idle drops from 800 to 500 rpm the engine shakes and then jumps to 1000, then repeats. The car will keep repeating this cycle until I turn off the car and let it cool down. The car idles fine if I put it in drive or reverse. The car is completely stock under the hood. The dealership has already changed the MAF sensor, throttler body, readjusted the valves, and have even tried draining out the gas and filling it with new gas. So my guess is they are resorting to changing out the gas they are running out of ideas. I know previous years of this car had a problem with idle hunting and it was fixed with a re-flash of the ECU, but the service manger said there computer wont let them re-flash mine cause it should have already been built with the re-flash applied. My car also never through up a CEL code or any other issue just the idle hunting.

I've already talked to Subaru of America's main office and the case manager there about replacing my car, but they seem to be jerking me around in an attempt to bide more time. Ideally I just want my car fixed instead of having to go through the whole process of switching out the car.

Any help or suggestions you guys can give would be greatly appreciated.

Thanks in advance

The first part of your problem were you said once it got hot it hunts and shakes idle issues, sounds maybe like coilpack problem maybe ? if the engine is miss firing you will get the shake and odd idle,
But without seeing the car or looking at it only can give you my opinion

Hope you get it sorted out soon so you can enjoy your car :)

I don't have any prior knowledge of similar cituations, but I can offer ideas.

Make sure coolant and engine oil, etc is correct, in the right place, and at the correct amount. Is you engine warmer than it should be or is it just at normal temps?

Wild theory: The computer sees that the engine is running too hot, so it attemps to cool it down by slowing down the engine. It lowers too much, notifying the computer, which raises the rpms to a higher than normal idle rpm. The cycle continues.

I had this happen on my 2015 as well, but after a while I haven't had it happen anymore. Could be maybe a break in thing? idk how many miles do you have on your car?

air, fuel or spark. Unlikely mechanical. They already worked on the other stuff, so all that is left really is spark/timing.

My car currently has about 6000 miles on it.

My car was doing that till I put a drop in filter. However it comes back again after my ECU resets due to dead battery thou not as bad as before.

Someone I know said his does that too till like 15k mile.

Does turning the AC off make a difference? It could be that the compressor is putting too much drag on the engine when it turns on and the idle goes down, then the compressor turns off and the idle over corrects.


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Th car will do it with the AC off. I don't think I've turned on my AC at all since I got the car.

Check this video and compare it with your symptom. If its the same thing, its been discussed long time ago.
https://m.youtube.com/watch?feature=...&v=rGu3zhBsBDA

http://www.ft86club.com/forums/showthread.php?t=8285

I read all those post when this issue first started I was hoping it would go away or part of the break in period. From what I can get from all the post on multiple forums is that the issue was resolved with a reflash of the ECU, but they told me that my car already received the reflash when the car was originally manufactured. From the video it seems to dip once and then go back to normal. My idle doesn't go back to normal unless i shut the car off and then start it back up. I have also yet to get a Check engine code. If it was just a dip when I stop and then goes back to normal I wouldn't worry to much. My concern is if its left the way it is will this lead to something prematurely failing down the line.

Then it sounds like you may have different issue. As far as I understood, you have fluctuations of needle up & down NOT like mine that the needle dips once. I guess posting a video may help you better. Hope you find solution soon~

I have a 15 aswell and it dips when I turn headlight on and even open the door any electric thing will make it dip buy not enough to stall it.