Light throttle stumble - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

venturaII · 08-21-2024, 11:46 AM

I recently installed an aftermarket catback on my '13 FRS (90k miles, all stock drivetrain), and with the slightly louder exhaust note now, I've noticed a light, brief stumble every time I shift gears, or tip into the throttle very lightly after coasting. It's most noticeable at lower rpms, when I'm just putting around town and shifting around 3k rpm. I just did an OBD scan and there's no codes stored, so I'm a little puzzled. I'm not sure how long it's been doing it since I can only really hear it and not feel it... I'm going to be taking the car on a 2000 mile trip in a couple of weeks, so I really don't want this to turn into a problem out on the road somewhere. I did a quick search on a few obvious keywords, but nothing close came up. Has anyone else experienced this? It it indicative of an upcoming failure?

Thanks -

Ultramaroon · 08-21-2024, 02:27 PM

Haven't seen you on in quite some time. I was getting a bit of stumble opening up from idle at a stop. Barely noticeable and on an older engine, would have ignored it.

Logged and saw fuel trims were a bit wonky. Figured I'd check the MAF. For fun, I left the engine running to see how it would respond to the MAF being disconnected.

Imagine my surprise when, just by touching the connector, the engine stumbled and recovered. Boom... found the problem. I've kept an eye on it, but it has been okay for over a year now.

Not saying that's your issue for sure. Just relating. Might help. Never know.

venturaII · 08-21-2024, 03:42 PM

Yeah, I've been keeping a low profile...just working and paying bills. Just sent my daughter to college yesterday...just me and the dog now. Guess we'll just stare at each other and fart...lol.

I was sort of thinking MAF in the back of my mind, but also was thinking TPS as well... I'll check the connector and maybe thake MAF off and hit it with cleaner and see what happens. Good to have a place to start though, thanks!

Ultramaroon · 08-21-2024, 09:00 PM

Quote:

Originally Posted by venturaII

Yeah, I've been keeping a low profile...just working and paying bills. Just sent my daughter to college yesterday...just me and the dog now. Guess we'll just stare at each other and fart...lol.

I was sort of thinking MAF in the back of my mind, but also was thinking TPS as well... I'll check the connector and maybe thake MAF off and hit it with cleaner and see what happens. Good to have a place to start though, thanks!

Unless you've installed one of those oiled filters, or suspect some other source of contamination, I'd leave the MAF alone. A quick visual will confirm. Mine is spotless after all these years.

A good fart is way underrated. All the best for your daughter!

venturaII · 08-21-2024, 10:48 PM

Too late..lol. MAF looked spotless, but I gave it a few shots of cleaner just for good measure. I use OEM style filters, so no oil contamination there. No real change after cleaning that I could tell. I'll keep poking around..

blsfrs · 08-22-2024, 12:28 PM

Quote:

Originally Posted by Ultramaroon

Unless you've installed one of those oiled filters, or suspect some other source of contamination, I'd leave the MAF alone. A quick visual will confirm. Mine is spotless after all these years.

A good fart is way underrated. All the best for your daughter!

Am I to understand that if you fart in front of your air intake , it will clean the MAF?

Ultramaroon · 08-22-2024, 01:33 PM

Quote:

Originally Posted by blsfrs

Am I to understand that if you fart in front of your air intake , it will clean the MAF?

Preparation is key. I've found that a combination of cruciferous vegetables coupled with equal parts blanched pinto beans works best.

blsfrs · 08-22-2024, 01:54 PM

Quote:

Originally Posted by Ultramaroon

Preparation is key. I've found that a combination of cruciferous vegetables coupled with equal parts blanched pinto beans works best.

You sound like a man who knows how to take care of his microbiome.

Ultramaroon · 08-22-2024, 03:38 PM

Quote:

Originally Posted by blsfrs

You sound like a man who knows how to take care of his microbiome.

Passing interest became a hobby. There are facebook groups for everything.

venturaII · 08-22-2024, 07:45 PM

Quote:

Originally Posted by blsfrs

Am I to understand that if you fart in front of your air intake , it will clean the MAF?

If you ate the vegetables that grow in my garden, your farts would peel wallpaper and make babies cry...

Ultramaroon · 08-24-2024, 03:38 AM

Aww... edited. I liked your original.

venturaII · 08-26-2024, 03:29 PM

Quote:

Originally Posted by Ultramaroon

Aww... edited. I liked your original.

Fixed, just for you. lol

Ultramaroon · 08-26-2024, 05:05 PM

Quote:

Originally Posted by venturaII

Fixed, just for you. lol

Yay!

08-21-2024, 11:46 AM	#1
venturaII Only users lose drugs. Join Date: Nov 2014 Drives: All the time Location: Shrewsbury upon Worcestershire Posts: 1,834 Thanks: 888 Thanked 1,078 Times in 681 Posts Mentioned: 3 Post(s) Tagged: 2 Thread(s)	Light throttle stumble I recently installed an aftermarket catback on my '13 FRS (90k miles, all stock drivetrain), and with the slightly louder exhaust note now, I've noticed a light, brief stumble every time I shift gears, or tip into the throttle very lightly after coasting. It's most noticeable at lower rpms, when I'm just putting around town and shifting around 3k rpm. I just did an OBD scan and there's no codes stored, so I'm a little puzzled. I'm not sure how long it's been doing it since I can only really hear it and not feel it... I'm going to be taking the car on a 2000 mile trip in a couple of weeks, so I really don't want this to turn into a problem out on the road somewhere. I did a quick search on a few obvious keywords, but nothing close came up. Has anyone else experienced this? It it indicative of an upcoming failure? Thanks - __________________ "To know a thing well, know it's limits. Only when pushed beyond its tolerances will true nature be seen." Amtal Rule

08-21-2024, 02:27 PM	#2
Ultramaroon not playing cards Join Date: Sep 2014 Drives: a 13 e8h frs Location: vantucky, wa Posts: 32,395 Thanks: 53,053 Thanked 37,228 Times in 19,308 Posts Mentioned: 1117 Post(s) Tagged: 9 Thread(s)	Haven't seen you on in quite some time. I was getting a bit of stumble opening up from idle at a stop. Barely noticeable and on an older engine, would have ignored it. Logged and saw fuel trims were a bit wonky. Figured I'd check the MAF. For fun, I left the engine running to see how it would respond to the MAF being disconnected. Imagine my surprise when, just by touching the connector, the engine stumbled and recovered. Boom... found the problem. I've kept an eye on it, but it has been okay for over a year now. Not saying that's your issue for sure. Just relating. Might help. Never know. __________________ service manuals

08-21-2024, 03:42 PM	#3
venturaII Only users lose drugs. Join Date: Nov 2014 Drives: All the time Location: Shrewsbury upon Worcestershire Posts: 1,834 Thanks: 888 Thanked 1,078 Times in 681 Posts Mentioned: 3 Post(s) Tagged: 2 Thread(s)	Yeah, I've been keeping a low profile...just working and paying bills. Just sent my daughter to college yesterday...just me and the dog now. Guess we'll just stare at each other and fart...lol. I was sort of thinking MAF in the back of my mind, but also was thinking TPS as well... I'll check the connector and maybe thake MAF off and hit it with cleaner and see what happens. Good to have a place to start though, thanks! __________________ "To know a thing well, know it's limits. Only when pushed beyond its tolerances will true nature be seen." Amtal Rule

08-21-2024, 10:48 PM	#5
venturaII Only users lose drugs. Join Date: Nov 2014 Drives: All the time Location: Shrewsbury upon Worcestershire Posts: 1,834 Thanks: 888 Thanked 1,078 Times in 681 Posts Mentioned: 3 Post(s) Tagged: 2 Thread(s)	Too late..lol. MAF looked spotless, but I gave it a few shots of cleaner just for good measure. I use OEM style filters, so no oil contamination there. No real change after cleaning that I could tell. I'll keep poking around.. __________________ "To know a thing well, know it's limits. Only when pushed beyond its tolerances will true nature be seen." Amtal Rule

08-24-2024, 03:38 AM	#11
Ultramaroon not playing cards Join Date: Sep 2014 Drives: a 13 e8h frs Location: vantucky, wa Posts: 32,395 Thanks: 53,053 Thanked 37,228 Times in 19,308 Posts Mentioned: 1117 Post(s) Tagged: 9 Thread(s)	Aww... edited. I liked your original. __________________ service manuals

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