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Old 08-30-2018, 04:54 PM   #1
John Natt
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Default 2015 Forester rough idle on cold start up

I have a 2015 Forester xt and on cold start ups it idles really rough especially if I turn the A/C on. It only has 37000 miles on it. Any one have any idea the problem. Thanks
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Old 08-30-2018, 07:55 PM   #2
yarrgh
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Have you reset the ECU or replaced the battery recently?
Recent maintenance?
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Old 08-31-2018, 11:56 AM   #3
John Natt
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I haven't done anything to it, I just bought it 2 weeks ago. You think the battery would do it?
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Old 08-31-2018, 12:08 PM   #4
Obviously Tyler
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Really hot, humid weather? My WRX will do this on days like that. Pretty normal as long it's just rough and not stalling.

Doesn't hurt to have it checked out though.
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Old 09-03-2018, 11:40 AM   #5
Charlie-III
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Quote:
Originally Posted by yarrgh View Post
Have you reset the ECU or replaced the battery recently?
Recent maintenance?
Quote:
Originally Posted by John Natt View Post
I haven't done anything to it, I just bought it 2 weeks ago. You think the battery would do it?
Clearing codes, disconnecting/replacing the battery all make the ECU lose "fine learning" which can affect how the engine idles and runs until it relearns.
How many cold starts and how many miles have you put on since you bought it?
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Old 09-03-2018, 04:30 PM   #6
John Natt
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Quote:
Originally Posted by Charlie-III View Post
Clearing codes, disconnecting/replacing the battery all make the ECU lose "fine learning" which can affect how the engine idles and runs until it relearns.
How many cold starts and how many miles have you put on since you bought it?
About 5 cold starts and about 1000 miles
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Old 09-03-2018, 04:31 PM   #7
John Natt
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Quote:
Originally Posted by Obviously Tyler View Post
Really hot, humid weather? My WRX will do this on days like that. Pretty normal as long it's just rough and not stalling.

Doesn't hurt to have it checked out though.
Yeah I have controlled temperature in my garage so I'm not sure its that but I really appreciate the info. Good to know. Thanks.
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Old 09-03-2018, 04:36 PM   #8
John Natt
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By the way thanks for the info everyone. It greatly appreciated.
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Old 09-04-2018, 10:26 AM   #9
Charlie-III
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Quote:
Originally Posted by John Natt View Post
About 5 cold starts and about 1000 miles
It should be close to done learning then. The cold starts is the biggie.
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Old 09-04-2018, 10:50 AM   #10
John Natt
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Cool thanks.
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Old 09-04-2018, 01:58 PM   #11
yarrgh
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What I was getting at is that newer cars seem to need to re-learn idle after an ECU reset. If you go to drive it too soon, that seems to mess with idle. There are threads on here somewhere on what to do. Pretty much let it warm up and don't touch the throttle for 10 mins or so.
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Old 09-29-2018, 09:08 PM   #12
John Natt
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Quote:
Originally Posted by yarrgh View Post
What I was getting at is that newer cars seem to need to re-learn idle after an ECU reset. If you go to drive it too soon, that seems to mess with idle. There are threads on here somewhere on what to do. Pretty much let it warm up and don't touch the throttle for 10 mins or so.
Ok thanks I'll try it out.
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Old 10-01-2018, 01:47 PM   #13
jasonwrx86
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Define rough like shaking?
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