2017 BRZ Intermittent Idle Dip
 

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.
Idle Dipping
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.

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.

2017 BRZ Intermittent Idle Dip
 

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

Hello Schweiz and welcome to the forum - :clap:

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.

:)

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.

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.

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?

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.

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.

@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.

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.

Just to echo what everyone else is saying, my FRS does the same thing, with the AC on at idle. It almost feels like the engine will die sometimes the RPMs drop so low. I’ve gotten used to it. The twins have a ton of “character” that’s for sure. [emoji28]


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>my17 in europe are the worst
also ots v4 based on euro tune have quite a shitty idle

Will the idle continue to dip after you come to a stop? Mine mostly isn't even when I'm coming to a stop, rather when I have been sitting still for a couple seconds.

I raised my idle to 950rpm and the a/c doesn't bother the car anymore. Even a clutch in from 6000rpm letting it sink all the way down, it doesn't stumbled to catch. It hesitates a little when idling, but nothing like the stumble it had when the idle rpm were at 650-700

In 6 years my engine has stalled just once because of this. Stopped at a traffic light, the idle dipped really low and the engine stalled. Started the car right up and had a CEL. Oh shit! My car is broken!
Went home and cleared the code with OFT. I forget what the code was. I think it was something about the vacuum.
Turns out it was just a hiccup and hasn't happened again. (Hasn't stalled, that is, it still dips all the time.)

Sorry for the noob question, but what does this mean?

Turn off the radio and listen. When the car is idling and you hear a click, that click is the AC compressor turning on. The idle dip always coincides with that click.

Is the idle something that can be set using OFT?

Yea I raised mine to 850 and it helped a ton.

Does the A/C compressor run even when the HVAC controls are turned all the way off by some chance? I remember reading somewhere that the compressor runs even when the A/C button is turned off, but I don't know how true that is.

In the video link I posted in the OP, I turned all the HVAC controls off to try an make sure the A/C was not causing the problem, plus I can't the click of the compressor kicking on. (maybe its extremely quiet?)

I agree, I am not a fan of the OTS v4 tunes at all. Mine tune is still based on the early stuff.

600 RPM idle is too low. I bumped mine to 950 as well since coming off the track, or driving the car on a sprited back road oil pressure was extremely low.

The compressor also turns on if you are in defrost mode.

In the tune, definitely

i successfully put 760rpm as hot idle in my tunes, but the real very rock steady is at 900rpm

The plate may be clean, but it's the bore that's important.

Ugh, I guess I'll go make a video for those that don't believe

@Schweiz

Might be a problem with idle/throttle learning.

Reset the ECU by pulling the battery and waiting for a bit. The first time you start the car, start it cold and let the car idle by itself for ~10 minutes without any accessories or A/C on. See if that helps.

If that doesn't help, try a reset again and do same as above, except run the AC while it is doing the idle learning.

I did this (no accessories on) back before I replaced my battery because I thought that may be the problem, but the problem resurfaced. Perhaps I will try what you suggested and let it idle with the A/C on.

Relearning idle speed without cleaning the throttle does nothing, because it's the same throttle and same engine, it'll idle at the same plate position, and if you've got a "step" of carbon/grime at that position, it'll constantly hunt around, as on the step the idle is too low, because it's not a smooth bore anymore, but a step, and above that step it'll idle too high.

This makes sense. I'll see about the throttle body again and give cleaning it a shot. Any tips you recommend?

That doesn't prove anything.
It's the cycling of the compressor that causes the dip. If the compressor is engaged when the engine idles, the engine already is compensating for the extra load and runs smoothly. It's when the engine is idling and the compressor suddenly engages and loads down the engine is when you get the idle dip.

Make another video. This time have the AC off and not in defrost with the engine idling. Now turn on the AC. You will hear the compressor engage and at the exact same time the idle will dip.

I'll betcha.

As per my earlier post

Don't spray intake cleaner into it, rather, spray on a rag and wipe clean.

Make sure to go around the bore and all the way behind the throttle plate. It's easier to unbolt it from the intake to reach the back easily, no need to take the coolant hoses off though, just get it loose to reach in, hold the plate open and make sure there's no buildup on the edge.

Firstly, if the compressor is cycling as fast as OP's video, it's not an idle problem that he's got, it's an ac problem

Secondly, no, you got what you wanted, take the L.

I might not have made it very clear earlier, but the A/C is not turned on during either of my videos. No A/C, no fans, no defrost, nothing. Even if I did turn the A/C on, it would still do the dip like that, same thing if I turn the A/C off again.

The video that @RZNT4R posted is exactly what my idle was like for the 200 miles after I replaced my battery, A/C or not.

Don't know if that changes anything, I just wanted to make sure that was cleared up.

Alright guys. I cleaned the throttle body and reset the ECU and went for a drive. At first the car was fine. Then after about 5 miles it started doing it again. Then randomly in the middle of the drive it went away. Then at the end of the drive it came back.

I recorded another video, this time showing that the A/C is off. It shows the in-car voltmeter spazing out, and it shows me switching the cars lights off and on just for the problem to continue.

Is this really just the stock tune? Or perhaps something like an alternator issue?

Thanks for all your guys' help so far.

Good follow up on your part - :thumbsup:

If you attach the multimeter to the battery with the engine running and all power consuming accessories turned off (especially the A/C) does the multimeter show a fluctuation in voltage coming from the alternator?

If so, you may wish to have the alternator bench tested.

If not, I would look to have the ECU re-flashed or get a store bought tune.