Can anyone give me some guidance on how to get rid of this CEL?

2004 WRX. My mods are STI UP, Stromung DP, Samco IC hose, STI muff, Protune. I have never had a CAI, BOV, MBC installed on the car. The P0171 is the only code that shows up. I'm getting horrible gas mileage (200 miles per tank), and the idle has a slight stumble. The car drives fine, but the boost is spiking a little bit. It has jumped up to about 17.1psi in 3rd-5th gear according to the accessport and then settles back to around 16.1psi.

So far, I've replaced my airfilter and made sure it was sealed. Cleaned the MAF sensor, cleaned the IACV and checked every vaccuum hose about 20 times. I've also installed and reinstalled the TMIC about 4 times to make sure the hoses were on tight and not leaking.

Anyone have any ideas before I drop some cash on a new primary 02 sensor? Also, if anyone is in the Campbell, san jose, los gatos area with a wrx, maybe we could meet up and park them side by side and I could trace all the lines under the hood to try and find any thing that doesn't look quite right?

Thanks

 

I have the same mods with protune and mine also jumps to 17.1 in 3-5th and goes back to 16.1 but then jumps back to 17.1 then back to 16.1 Why?

 

check and see if your bov plug is still there, it happend on my friends sti his came loose and he got the same code.

 

Do you mean the hose attached to the BOV?

 

i have had the same code for a month and a half now. same story, cant find anyhting wrong?!

 

I really want to solve this becaue I'm getting horrible gas mileage, and gas ain't cheap!

My car was running lean with the Cobb CA stage 2 map, and Mike @ gruppe-s fixed that with the protune a couple months ago. I'm baffled. Maybe a fuel filter, front o2 sensor? Maybe it's still running lean, but I never had a CEL before the protune. I'm about to give up and take it to a mechanic so they can charge me a diagnostic fee and labor.

 

Bring it by so I can take a look at it, no diagnostic fee and it might be something easily fixed.

Mike

 

Nice!! Thanks Mike, I appreciate the offer.

PM sent

 

i changed out my fuel filter, fuel pressure regulator and well as my front o2 sensor and have had no luck in fixing it. hopefully that will narrow it down a little bit.

-Justin

 

Front 02 sensor

 

any updates on the fix of the problem? please LMK as soon as possible.

 

Not yet, but I'm going to take it to Gruppe-s next week and Mike is going to take a look at it. I'll keep you posted.

 

thanks!

 

I've been having the same problem on my02 wrx. Pulled the PO171 code twice in the last two months and experiencing wide boost flux. Recently changed the fuel filter and new sparks with only 10k on 'em

 

this is the problem my cousins subaru wrx is having. twice now the dealership has changed the 02 sensor. it's now in for it's 3rd time, hopefully they realize it's something else.

wastegate maybe? boost creep?

-Gagan