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Old 12-08-2017, 10:05 AM   #1
Mgillis86
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Default Running lean...

Hey guys so my car recently sat for almost a month I ran it a few times for about 10 minutes here and there and the next week I drove it and the car doesn’t feel right, I’ll be cruising just barely on the throttle and I can feel the car buck as if it’s not getting enough fuel so I gave it a few days to see if it would go away. Few days later still having the same issue and I got a cel on the dash so ran the code on my Accessport and I’ve got code P0171
Which means the fuel trim is running lean (too much air not enough fuel) I don’t know out of nowhere why it would start running lean. I cleaned the maf sensor and reset the ecu still have the same problem. Any suggestions? Sorry for the long story
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Old 12-11-2017, 02:46 AM   #2
dokalanyi
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Hello,
The AP should be able to log various parameters. Log AFR, and fuel compensations. I've never used Cobb (I use Romraider), but it should have those.

It could be a vacuum leak, but it's likely a failing fuel pump. Logging fuel trims will shade more light
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Old 02-20-2018, 11:43 AM   #3
Mgillis86
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Bump, replaced front o2 sensor, replaced spark plugs with brand new ones, had all boost/vacuum leaks taken care of. Got the car in the air the other week looked and listened for exhaust leaks found none. Fuel filter also been replaced with a new one. Problem still persists but the cel hasn’t come back on ever since I reset the ecu. Car still runs weird, has a hard time building boost but will eventually get up to 18 psi but it’s sluggish. I’m thinking my up pipe is clogged. Any other suggestions?
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Old 02-24-2018, 07:13 AM   #4
Crispy 1
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I assume since you mentioned the uppipe being clogged that it's a Bugeye?

I have been dealing with almost the exact same problems and have done the same fixes and more. I think I have finally gotten it mostly fixed.

I just put installed some Mishimoto intercooler hoes, deleted the throttle body coolant, cleaned the knock sensor, changed the pcv valve, cleaned inside of intercooler and anything else I could think of and the car seems to be a lot better. I didn't reset the ecu this last time but the fuel trims are starting to come down and it feels better in every gear and every rpm. I can drive a gear higher than I have been the last 2 months!

Gonna change the turbo inlet tomorrow and do a compression test just to be safe, then once my coil packs get here change all 4 and hopefully be done with it. If you plan on keeping it you might as well throw the parts at it. Mine is almost to 150,000 and needs everything it's gotten anyways so I don't feel to bad about it.

Good luck!
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Old 03-05-2018, 09:06 PM   #5
Mgillis86
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Quote:
Originally Posted by Crispy 1 View Post
I assume since you mentioned the uppipe being clogged that it's a Bugeye?

I have been dealing with almost the exact same problems and have done the same fixes and more. I think I have finally gotten it mostly fixed.

I just put installed some Mishimoto intercooler hoes, deleted the throttle body coolant, cleaned the knock sensor, changed the pcv valve, cleaned inside of intercooler and anything else I could think of and the car seems to be a lot better. I didn't reset the ecu this last time but the fuel trims are starting to come down and it feels better in every gear and every rpm. I can drive a gear higher than I have been the last 2 months!

Gonna change the turbo inlet tomorrow and do a compression test just to be safe, then once my coil packs get here change all 4 and hopefully be done with it. If you plan on keeping it you might as well throw the parts at it. Mine is almost to 150,000 and needs everything it's gotten anyways so I don't feel to bad about it.

Good luck!
Hey got a catless uppipe installed, also got my throttle cable tightened still same issue. however 2 weeks ago i logged my DAM for once on my accessport and it was at 9 after a 3rd gear pull. I figured i had gotten a bad batch of gas. Got 93 from shell a few days later and reset the ecu. DAM is now at 12.
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Old 03-05-2018, 09:21 PM   #6
subaru_gc8
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id shoot for a boost leak, are you using the stock turbo inlet?
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Old 03-06-2018, 10:21 AM   #7
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This could be a bad or dirty maf sensor. If you get a new one get it from subaru, it seems expensive but it is absolutely worth it.

You could try replacing your fuel filter.

your turbo inlet could have a break in it around where the hose clamp is, causing excess air to get sucked in causing the lean condition.

Look at your fuel trims, af learning ABCD and post them here, they can give some indication to potential problems.
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Old 03-10-2018, 05:17 PM   #8
Mgillis86
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Quote:
Originally Posted by subaru_gc8 View Post
id shoot for a boost leak, are you using the stock turbo inlet?
yes stock inlet
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Old 03-10-2018, 05:18 PM   #9
Mgillis86
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Quote:
Originally Posted by 86Dreams View Post
This could be a bad or dirty maf sensor. If you get a new one get it from subaru, it seems expensive but it is absolutely worth it.

You could try replacing your fuel filter.

your turbo inlet could have a break in it around where the hose clamp is, causing excess air to get sucked in causing the lean condition.

Look at your fuel trims, af learning ABCD and post them here, they can give some indication to potential problems.
I have replaced my fuel filter with a new one, ive cleaned my filter and MAF. my fuel trims seem to be fine from what i can remember
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Old 03-14-2018, 02:16 AM   #10
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Quote:
Originally Posted by Mgillis86 View Post
I have replaced my fuel filter with a new one, ive cleaned my filter and MAF. my fuel trims seem to be fine from what i can remember
uhh if you are getting a p0171 your fuel trims are not okay..... the computer is adding fuel because it reads that you are running lean
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Old 03-14-2018, 02:24 PM   #11
Mgillis86
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Quote:
Originally Posted by subaru_gc8 View Post
uhh if you are getting a p0171 your fuel trims are not okay..... the computer is adding fuel because it reads that you are running lean
i did get that code a few months ago and got all my boost leaks fixed and that cel hasnt come back since
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Old 03-25-2018, 10:28 PM   #12
Mgillis86
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Bump, got some good news. DAM is now at 16 after cleaning MAF and resetting ecu. Car still feels boggy i have a strong suspicion my turbo is going up. has a rough time building boost and burning a decent amount of oil which i can see coming out the back of my car
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Old 03-26-2018, 01:23 PM   #13
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Just wondering how old is the gas, sitting for a month but when did you fill up last? I have noticed with this 10% ethanol gas that it eats up components much faster then the old stuff. I had a civic sit for 3 months with CA pump and it froze the fuel pump!<br />
<br />
Also was it stored outside? Some rodents may have grounded some wires for you if so.

Last edited by PVNRT; 03-26-2018 at 01:25 PM. Reason: added info
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Old 03-26-2018, 02:44 PM   #14
subaru_gc8
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if you're burning oil, I would have to say a mild misfire is occurring. sometimes it doesnt set off the light, until it get really bad.
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Old 03-27-2018, 09:31 PM   #15
Mgillis86
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Quote:
Originally Posted by PVNRT View Post
Just wondering how old is the gas, sitting for a month but when did you fill up last? I have noticed with this 10% ethanol gas that it eats up components much faster then the old stuff. I had a civic sit for 3 months with CA pump and it froze the fuel pump!<br />
<br />
Also was it stored outside? Some rodents may have grounded some wires for you if so.
the car sat for almost 2 months during winter. I wonder if its my fuel pump though it feels as if the car isnt getting the necessary fuel it needs.
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Old 03-28-2018, 11:13 AM   #16
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Quote:
Originally Posted by Mgillis86 View Post
the car sat for almost 2 months during winter. I wonder if its my fuel pump though it feels as if the car isnt getting the necessary fuel it needs.

If its the original pump you should replace anyway at that mileage, I am going through similar issues at 202k with original everything, I consider the fuel pump a wear item after 150k. One or more injectors might be getting tired at that age too.

It becomes a time vs money issue....do you have time to log fuel pressure or add a mechanical gauge? Or do you have the money to replace parts blindly and maybe send out injectors to get cleaned and balanced?
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Old 03-28-2018, 11:23 AM   #17
Mgillis86
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Quote:
Originally Posted by PVNRT View Post
If its the original pump you should replace anyway at that mileage, I am going through similar issues at 202k with original everything, I consider the fuel pump a wear item after 150k. One or more injectors might be getting tired at that age too.

It becomes a time vs money issue....do you have time to log fuel pressure or add a mechanical gauge? Or do you have the money to replace parts blindly and maybe send out injectors to get cleaned and balanced?
I had my fuel pressure checked a month ago it was 35psi at idle. I had plans of getting an sti turbo this summer with a bigger top mount as well as bigger injectors.
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Old 04-09-2018, 10:17 PM   #18
Mgillis86
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bumpp
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Old 04-10-2018, 11:41 AM   #19
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FYI, it's never a maf sensor for the most part. AFR changes based off of two things. Fuel and spark.

Noticed you said you did you FF already so I recant that.. get a new fuel pump since there's no tune needed for it.

Spark issues normally = running rich
Fuel issues normally = running lean (unless it's the fuel pressure regulator)

So it's either your injectors being clogged, fuel filter, or dying fuel pump. Start by getting a new fuel filter and go from there
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Old 04-16-2018, 12:10 AM   #20
Mgillis86
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Quote:
Originally Posted by jthatch12 View Post
FYI, it's never a maf sensor for the most part. AFR changes based off of two things. Fuel and spark.

Noticed you said you did you FF already so I recant that.. get a new fuel pump since there's no tune needed for it.

Spark issues normally = running rich
Fuel issues normally = running lean (unless it's the fuel pressure regulator)

So it's either your injectors being clogged, fuel filter, or dying fuel pump. Start by getting a new fuel filter and go from there
I appreciate the advice! ill order a new fuel pump and see what comes of it
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