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Old 01-18-2013, 09:51 PM   #1
Ilovecugars
Scooby Newbie
 
Member#: 299442
Join Date: Oct 2011
Location: Southern Ontario Canada
Vehicle:
2005 Forester XT

Default Idel afr unsteady

Hi guys.
I have a 05 Fxt with a stage 3 setup and a pro tune through AP. The car have been like this for a while and has worked well. However lately it has had rough idel and has been a tough one for me to figure out.
At idel is the only time it does this, the rpm are steady within about 50rpm either way. But monitoring the afr I see it is jumping around a fair bit. It will fluctuate from 14 to around 15.5 and anywhere in between and when it jumps around it is causing a roughness felt through out the car. Once the car is rolling it has no issues and works great and even seems to improve a bit when the AC is on and has no idel issue when it is cold warning up on high idel.
I was having some surging issues at part throttle so I replaced my front o2 which did solve that issues but did not fix the idel. At least I can narrow it down to know that sensor is not at fault.
If any one has any suggestions of where to look for causes to this problem it would be a great help. The only ideas I have at the moment are perhaps a leaking bpv as it is stock or maybe a bad maf sensor. Both of which I can switch from my wifes car to rule those out.
One again any one with experience with this some help would be awesome.
Thanks
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Old 01-21-2013, 08:55 AM   #2
Cobb Tuning
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Join Date: Mar 2001
Location: Austin, DFW, Portland, SOCAL
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Originally Posted by Ilovecugars View Post
Hi guys.
I have a 05 Fxt with a stage 3 setup and a pro tune through AP. The car have been like this for a while and has worked well. However lately it has had rough idel and has been a tough one for me to figure out.
At idel is the only time it does this, the rpm are steady within about 50rpm either way. But monitoring the afr I see it is jumping around a fair bit. It will fluctuate from 14 to around 15.5 and anywhere in between and when it jumps around it is causing a roughness felt through out the car. Once the car is rolling it has no issues and works great and even seems to improve a bit when the AC is on and has no idel issue when it is cold warning up on high idel.
I was having some surging issues at part throttle so I replaced my front o2 which did solve that issues but did not fix the idel. At least I can narrow it down to know that sensor is not at fault.
If any one has any suggestions of where to look for causes to this problem it would be a great help. The only ideas I have at the moment are perhaps a leaking bpv as it is stock or maybe a bad maf sensor. Both of which I can switch from my wifes car to rule those out.
One again any one with experience with this some help would be awesome.
Thanks
Top of the list would be a post-MAF intake tract leak. I would get a pressure or smoke test of the intake tract done and fix any leaks you find and then reset the ECU via the AccessPORT. If you have a version 2 AccessPORT, you can take a look at the A/F Learning 1 A,B,C,D values (via Live Data function or data logging) which may give you more information as it pertains to a possible fueling issue.

Bill
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