Check engine - P0171

PSUENGR

Member
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2003.5 MSP
So I've been getting this code (P0171 - bank 1 running lean) intermittently since the spring. The light will come on and then turn off 2 or 3 days later and stay off for around a week before it pops up again. When it first appeared, my mechanic ran a smoke test and I don't have any vacuum leaks. He also cleaned the MAF at that time. Fast forward to now and I got my bi-annual emission inspection notice so I'm going to go today since the light is off, but I'm not too confident that it will pass since the codes are still going to be in there.

Assuming I do need to fix this, I'm thinking my #1 culprit at this point is the WGA. I haven't gotten around to testing the old one because I really didn't want to take off the plastic underbody, but it looks like now is going to be that time.

First, is there any easy way to get at the vacuum line to test the WGA without removing the underbody?
Second, is there anything else I should be checking before I look at the WGA?
Finally, if the WGA is bad, should I go with the Forge unit (~$135) or the generic fixed boost one sold on Atpturbo.com (~$65)?

Background info: the car has ~108k miles on it and is bone stock save for a corksport exhaust (no cat) and new tokico illumina shocks & springs. In the last year my daily commute has changed from a ~50 mile round trip mostly interstate drive to a 6 mile round trip drive around small/slow streets (35mph limit) to the train station.
 
The stock vaccum line for the WGA goes to a T fitting. located on the driver side of the motor. You can dissconnect it there and check to see if the WGA is ripped by blowing into the line. You should not be able to build enough pressure with your mouth to allow any air to pass through. If you can blow through the line then it is a faulty WGA. If you cannot blow through it could still be a faulty WGA or a flaper valve in the turbo not sealing properly.

Some other things to look at are the VTCS and VICS solenoids on the intake manifold. They should have Mitsubishi emblems on them.... or mine do atleast. I tested mine with a multi meter for resistance and replaced the VCTS solenoids because it was out of spec Here is the documentation I used . Someone might have something better.
 
thanks, i'll have to give that a try tomorrow or Sunday. I'm not sure I will be able to get the vacuum line off without damaging it as it is also original and i'm sure quite brittle by now. Fingers crossed that I can or else I will be taking off the underbody regardless as I definitely won't be able to get a new line on....

Coincidentally, i passed the emission test, but I still need to get this sorted out because if it is a bad WGA I could be running significantly more boost than I should be (no boost gauge) and that won't be good since I plan to keep this car as a DD for quite a while longer (looking for an elise or waiting for a BRZ STi :) )
 
You can find cheap t fittings and vacuum line at your local parts store. Worst case you bust the vacuum line and t fitting, Go to parts store spend 7-8 bucks and replace the broken peices
 
Did you use the non fouler trick with your catless exhaust?

I did. I'm assuming this running lean code is due to extra air (boost) and is unrelated to the exhaust and non-fouler since that worked fine for a couple years before the code tripped.

I just got around to checking the WGA now since it has been going on and off all winter and I can blow air through it so I'm assuming the WGA is bad.
 
I did. I'm assuming this running lean code is due to extra air (boost) and is unrelated to the exhaust and non-fouler since that worked fine for a couple years before the code tripped.

I just got around to checking the WGA now since it has been going on and off all winter and I can blow air through it so I'm assuming the WGA is bad.

Definitely need to replace the WGA. No way should you be able to produce enough pressure with your mouth. Careful because you are going to be overboosting.
 
Replaced the wga on Saturday and so far so good.

Is there any way to verify what boost pressure I'm running now since I don't have a boost gauge installed?
 
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