2017 BRZ Intermittent Idle Dip

[RZNT4R]

Originally Posted by Schweiz

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?

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

[EndlessAzure]

@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.

[Schweiz]

Originally Posted by EndlessAzure

@Schweiz
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.

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.

[RZNT4R]

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

[RZNT4R]

Originally Posted by Schweiz

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.

[Schweiz]

Originally Posted by RZNT4R

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?

[WNDSRFR]

Originally Posted by RZNT4R

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.

[RZNT4R]

Originally Posted by Schweiz

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

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.

[RZNT4R]

Originally Posted by WNDSRFR

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.

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.

[Schweiz]

Originally Posted by WNDSRFR

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.

Originally Posted by RZNT4R

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

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.

[Schweiz]

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

, 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.

[humfrz]

Originally Posted by Schweiz

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

, 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 -

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.

[Schweiz]

Originally Posted by humfrz

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.

This was pretty much what I was thinking as far as the next steps. Thanks to you and everyone else for the insight.

[tomm.brz]

it s the PI inietting at idle intermittently

steve99 explainef how to fix