|
Engine, Exhaust, Transmission Discuss the FR-S | 86 | BRZ engine, exhaust and drivetrain. |
![]() |
|
Thread Tools | Search this Thread |
![]() |
#1 |
Senior Member
Join Date: Jun 2017
Drives: 2017 PP BRZ
Location: California
Posts: 209
Thanks: 56
Thanked 53 Times in 43 Posts
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
|
RPM Fluctuation At Idle
Hello,
My friend is having rpm fluctuation at idle. After helping him do some research, it turns out this is a common problem for this platform. I have never had rpm fluctuation at idle. We started with bleeding the coolant since possibly the system had air in it. Nope still fluctuated. We tried cleaning the throttle body. Nope still fluctuated. We changed the PCV valve. Nope still fluctuated. We did the smoke test. Nope still fluctuated. We still need to check : fuel trims 10% give or take possible transmission module needs an update? Possible head gasket? Mods : Catback exhaust PCV catch can grimmspeed drop in filter Boost -19 idle (read from p3 gauge) AFR 14.4 - 14.7 cruising (read from p3 gauge) maybe @steve99 can chime in? The car has 20k miles on the odometer 2018 Manual transmission The car is out of warranty. I just want him happy |
![]() |
![]() |
![]() |
#2 | |
Proud of BOXER
Join Date: Dec 2012
Drives: Subaru Boxer
Location: Bay Area
Posts: 8,149
Thanks: 7,083
Thanked 6,854 Times in 3,677 Posts
Mentioned: 199 Post(s)
Tagged: 0 Thread(s)
|
Stock tune?
Try cleaning the MAF, with MAF cleaner spray.
__________________
Quote:
|
|
![]() |
![]() |
The Following User Says Thank You to Clipdat For This Useful Post: | Teseo (07-07-2023) |
![]() |
#3 |
Senior Member
Join Date: Jun 2017
Drives: BRZ Yellow, 2019 Ranger, 2011 Evora
Location: Dallas
Posts: 1,703
Thanks: 354
Thanked 1,486 Times in 779 Posts
Mentioned: 14 Post(s)
Tagged: 1 Thread(s)
|
It’s a BRZ thing, you can not fix an engineering mistake.
|
![]() |
![]() |
The Following 3 Users Say Thank You to Grady For This Useful Post: |
![]() |
#4 |
Geo Tyrebighter Esq
Join Date: Mar 2013
Drives: '13 scion fr-s
Location: pnw
Posts: 4,279
Thanks: 6,578
Thanked 5,180 Times in 2,263 Posts
Mentioned: 42 Post(s)
Tagged: 1 Thread(s)
|
Starting in '17, the charging system went to intermittent battery charging.
The ECU monitors use and will turn the alternator on and off depending on current need. That will put more or less load on the engine depending if it's charging or not. Is alternator output load dependant ???
__________________
--
"I gotta rock." -- Charley Brown |
![]() |
![]() |
The Following 3 Users Say Thank You to bcj For This Useful Post: |
![]() |
#5 |
Bottled FRS
Join Date: Jul 2015
Drives: 2016 manual frs
Location: Dallas Tx
Posts: 79
Thanks: 20
Thanked 31 Times in 17 Posts
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
|
I am not sure if this is a different issue than the typical idle fluctuation where the rpm will drop almost stall and then rise again. If this is what you are talking about it can be tuned out. There was a popular user here a few years ago that uploaded his tables for this in ROM raider. I used them, and my idle stays between 750-800 RPM no dropping/ stalling feel.
|
![]() |
![]() |
![]() |
#6 |
Senior Member
Join Date: Jan 2018
Drives: Crapcan
Location: Oregon
Posts: 11,415
Thanks: 18,640
Thanked 16,674 Times in 7,558 Posts
Mentioned: 110 Post(s)
Tagged: 0 Thread(s)
|
How much fluctuation are you talking about here? 50rpm, 400rpm, almost stalling?
Think about the things the affect running condition at idle, none of the things you have done have anything to do with it. Fuel trims should be around +/- 5% or so. 10% is very high. AFR at cruise doesn't tell us anything about idle. It's either vacuum leak, metering, or a load is being placed on the engine like AC or the alternator as mentioned above. It's a random thing on some cars, as long as it is not too severe it is a "feature." There are tons of threads on it.
__________________
"Experience is the hardest kind of teacher. It gives you the test first and the lesson afterward." -Oscar Wilde.
|
![]() |
![]() |
The Following User Says Thank You to NoHaveMSG For This Useful Post: | Ultramaroon (07-10-2023) |
![]() |
#7 |
Senior Member
Join Date: Apr 2019
Drives: 86 GT
Location: Malaysia
Posts: 369
Thanks: 239
Thanked 213 Times in 109 Posts
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
|
https://www.ft86club.com/forums/showthread.php?t=144716
Posting my findings before if that may help.
__________________
DIY stuff at Compelica Works
|
![]() |
![]() |
The Following User Says Thank You to Compelica For This Useful Post: | NoHaveMSG (07-10-2023) |
![]() |
#8 |
Bottled FRS
Join Date: Jul 2015
Drives: 2016 manual frs
Location: Dallas Tx
Posts: 79
Thanks: 20
Thanked 31 Times in 17 Posts
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
|
https://www.ft86club.com/forums/showthread.php?t=139501
Use this thread it completely solved idle issues for me and he posted his tables. Do some testing and you can eliminate it completely. |
![]() |
![]() |
The Following User Says Thank You to Texas2016Frs For This Useful Post: | NoHaveMSG (07-10-2023) |
![]() |
#9 |
Senior Member
Join Date: Jun 2017
Drives: 2017 PP BRZ
Location: California
Posts: 209
Thanks: 56
Thanked 53 Times in 43 Posts
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
|
Afr jump around at idle. Definitely hunting around more than usual. Fuel trims look good IMO. The ac is not on. The HVAC system is off. The defroster is not on. The radio is not on. All these things put a load on the alternator/battery but they're not on. Wouldnt the smoke test detect a vacuum leak? We are talking about a 75 / 100 rpm jump or so. I will have my friend send a video when he gets the chance.
|
![]() |
![]() |
![]() |
#10 |
hey you, yeah you <3
Join Date: Jul 2012
Drives: 2014 37J FR-S
Location: Monterey County, CA
Posts: 2,713
Thanks: 905
Thanked 1,258 Times in 809 Posts
Mentioned: 38 Post(s)
Tagged: 3 Thread(s)
|
My 2014 had similar issue with RPM’s sometimes making it hard to take off because RPM would drop more than in my other vehicles. I cleaned battery terminals thoroughly and used battery terminal scraper(?) to remove corrosion and grudge build up from 5 or so years, cleaned MAF and throttle body butterfly buildup and allowed computer to go through its idle relearn after unplugging battery for 30 min. 120 miles later and it fixed much of the RPM fluctuations. 3000 miles now and car is doing amazing. I have a Optima red top as well, since, the original battery would leave me stranded after 5 years of use. Give that a try, may do the trick.
__________________
Got my TRD wheels and TRD louvers. Thanks!!!
|
![]() |
![]() |
The Following User Says Thank You to Packofcrows For This Useful Post: | Clipdat (07-10-2023) |
|
|
![]() |
Thread Tools | Search this Thread |
|
|
![]() |
||||
Thread | Thread Starter | Forum | Replies | Last Post |
RPM fluctuation..... | NickFRS | Issues | Warranty | Recalls / TSB | 163 | 01-12-2022 05:26 PM |
Idle rpm fluctuation with oft stage2+ e85 tune(ac off) | jiffyjhn | Software Tuning | 1 | 12-06-2020 05:23 PM |
Frs idle rpm fluctuation, vibration and fan/compressor noise, normal? | szjalo | Scion FR-S / Toyota 86 GT86 General Forum | 15 | 10-06-2018 05:49 PM |
IDLE FLUCTUATION TSB.... | 5AD86D | Issues | Warranty | Recalls / TSB | 0 | 10-18-2016 07:55 AM |
Idle Fluctuation FIX | empower-auto | Issues | Warranty | Recalls / TSB | 2 | 09-14-2012 03:36 PM |