2017 BRZ Intermittent Idle Dip

[Schweiz]

Hey everyone, I'm new to owning a twin and new to the forums here. I recently acquired a 2017 BRZ PP and I am loving it. The only thing that hasn't been very lovely has been an idle dip that started occurring a couple of days after I got the car. I had been doing a lot of research on the issue and it seems like this was a common problem for some of the earlier BRZ/FRS cars. However, I would think after the TSB that was released, this problem would not occur on the 2017+ cars (please correct me if I'm wrong).

Once the problem had been around for a couple of days, I decided to replace the battery (which was the original 2017 factory battery) because the voltmeter showed under 12v at times even with the car running. Once I replaced the problem was gone instantly and the voltmeter held steady. The idle did not drop anymore and the car idled like it should. However, about a week/200 miles after doing the battery change, the problem has resurfaced. Even with the lights on and the voltmeter at 14v, the car's idle will still dip and cause the car to shake roughly.

However, strangely this is not the case all of the time. Sometimes the car will idle perfectly fine, then just start doing this at the next stoplight and continue for the rest of the drive, then for some reason, when I pull into my driveway and sit, it won't dip. Other times it will dip at idle from departure to return. Sometimes it won't do it at all.

I've got a video of the idle dipping (you can even see the dash lights dim at times when it dips) and a perfectly normal idle.

Also, just to be thorough, the car has a little over 17,600 miles on the odometer.

I was very excited when I replaced the battery and thought I had fixed the issue. Now I'm bummed out because my new baby is acting strange again

Any insight is much appreciated.

[tomm.brz]

normal
stock tune sucks

[Schweiz]

Originally Posted by tomm.brz

normal
stock tune sucks

If it is truly the stock tune, would an OFT off-fhe-shelf stage 1 tune remedy it? For some reason I just really can't stand it dipping down like that.

[Yoshoobaroo]

OFT stage 1 fixes a lot of small driveability issues. The dips are much reduced and less severe. Throttle response is much better too.

[humfrz]

Originally Posted by Schweiz

Hey everyone, I'm new to owning a twin and new to the forums here.

Any insight is much appreciated.

Hello Schweiz and welcome to the forum -

Does your car have any power mods?

Are you sure the A/C compressor is not cycling, causing the idle to vary?

You might try putting your voltmeter on the battery when the car is running to see if their is any correlation between when the alternator is charging and the idle is fluctuating.

Did you get your last tank of gas where you normally do?

I doubt the ECU is still learning after the battery change, but, maybe it's a slow learner -

I hope you get it sorted out.

[RZNT4R]

Originally Posted by tomm.brz

normal
stock tune sucks

It's not "normal" because my stock '17 doesn't do that, idles like a champ at 600rpm.

With a modern car that has idle stability problems, ALWAYS start by cleaning the throttle body and plate. Don't spray intake cleaner into it, rather, spray on a rag and wipe clean.

[Schweiz]

Originally Posted by humfrz

Hello Schweiz and welcome to the forum -

Does your car have any power mods?

Are you sure the A/C compressor is not cycling, causing the idle to vary?

You might try putting your voltmeter on the battery when the car is running to see if their is any correlation between when the alternator is charging and the idle is fluctuating.

Did you get your last tank of gas where you normally do?

I doubt the ECU is still learning after the battery change, but, maybe it's a slow learner -

I hope you get it sorted out.

The car is bone stock and I've made sure the A/C compressor was not cycling. In fact, it will do this idle issue with the A/C on and off.

I got my last tank of gas at the exact same spot as last time.

Whats strange is that it seems like this may have started up again after the ECU was done learning.

[Schweiz]

Originally Posted by RZNT4R

With a modern car that has idle stability problems, ALWAYS start by cleaning the throttle body and plate.

When the problem first occurred, I was thinking it could be the throttle body, but when I inspected it, the the plate was still super clean. Is it still worth cleaning it to see if it makes a difference?

[tomm.brz]

Originally Posted by RZNT4R

It's not "normal" because my stock '17 doesn't do that, idles like a champ at 600rpm.

With a modern car that has idle stability problems, ALWAYS start by cleaning the throttle body and plate. Don't spray intake cleaner into it, rather, spray on a rag and wipe clean.

i don t believe it
do a video of idling with ac on hot coolant and i ll do believe it

[Yoshoobaroo]

Originally Posted by tomm.brz

i don t believe it
do a video of idling with ac on hot coolant and i ll do believe it

Agreed. I haven’t found a stock twin in the wild without an idle dip.

[radroach]

My idle always dips a bit when there's a load put on the alternator. It dips the most if I roll my windows all the way down, and then press the down switch again, instant dip.

Turn off all electrical accessories and test it. Turn off headlights, turn off radio, turn off all AC fans, make sure your rear defroster is off.

[radroach]

@Schweiz I've seen that newer 86's use a different charging circuit. It's supposed to be a smart charger that doesn't put load on the alternator while its idling.

[WNDSRFR]

Yeah
Mine's been doing the idle dip thing since day one. But mine is definitely caused by the AC cycling. If I come to a stop just as the AC turns on the idle will dip every time.

[Yoshoobaroo]

Originally Posted by WNDSRFR

Yeah
Mine's been doing the idle dip thing since day one. But mine is definitely caused by the AC cycling. If I come to a stop just as the AC turns on the idle will dip every time.

Yes coming to a stop with AC on does it every time.