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Old 11-07-2002, 12:32 PM   #1
Hank3
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Default System Too Lean Revisted: P0171 CEL

I've had this CEL on constantly for the past few months now and as you all know CELs can really be bothersome while you're driving. I originally thought it could be my MRT CAI causing this (still could be), but I recently took off the CAI and put the stock intake back on, but I'm still seeing this CEL pop up every 30-40 miles of driving. I did a little more research on i-club for this CEL and remembered that some of you have mentioned that it could be a vacuum leak. I'm starting to wonder if it could be a vacuum leak(s) that's causing this. I have noticed that the CEL always comes on during idle at a stop light or when my car is cooling down during the Turbo Timer countdown. So could I assume with confidence that it is a vacuum leak causing this CEL? If it is, could someone please guide me to where I need to be checking for the leak? I read that it could be the vacuum hose to the BOV? If so, which one is that? If the leak could be elsewhere, could someone guide me to where I could check? Thanks in advance for any help...
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Last edited by Hank3; 11-07-2002 at 04:03 PM.
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Old 11-07-2002, 02:32 PM   #2
jaxscuby
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Have a Nice Day? did you rest the ecu?

Hanksan,
after you replace CAi with stock one did you disconnect the battery for an hour or so and then reconnect?

you never know..


you know who..
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Old 11-07-2002, 02:39 PM   #3
Hank3
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Ben Miyagi - after I installed the stock intake, I had my brother clear the code with his OBD-II, but then the CEL came on within 30 or so miles. I then disconnected the battery for about 30 minutes or so and then the CEL came back. Took it into the dealer this week, they cleared the code, but attributed it to my MRT exhaust system, but I don't think that's it. CEL has came on since Tuesday at the dealer, so I cleared it again last night at my brothers and then it takes us to today. It just came on while going to lunch at a stop light. Go figure HELP!!!
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Old 11-07-2002, 03:00 PM   #4
PaulRex
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Well, there is a vacuem hose coming out of a nipple on the right side of the gold BOV on the IC.. The return/resirc. line runs off of the BOV under neath the IC to the intake, you could check those lines.. There are some vacuem line connections on the turbo inlet hose. There are a bunch of others, some on the intake manifold.(Hopefully someone can explain there location better than I can) Some other places you could check would be the turbo outlet, and Y connections on the IC(maybe save that for last option since you have to take the IC off for that one). Check your connections again with your airbox hoses/clamps(which you did already prob..)
Maybe, borrow someones MAF sensor for a day(it unclips in like second) and see if you still have a problem, or if they do. Then you would know your MAF sensor is broken.. That sounds alittle unorthodox, but just an idea.

Does your car idle funny, or lumpy/off? Anytime I've heard an wrx with an vacuem leak it idles alittle bit off.

Good Luck
Paul

Last edited by PaulRex; 11-07-2002 at 03:07 PM.
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Old 11-07-2002, 04:08 PM   #5
Hank3
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Paul - I notice rough idling at times, but I don't think it's anything out of the ordinary as I have STi Engine Mounts (probably amplifies the problem of any kind of rough idling), but then I hear it's normal to get rough idling at times due to our boxer engine. I don't know what truly constitutes as "Rough Idling" with the condition/factors given...
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Old 11-08-2002, 08:30 AM   #6
Hank3
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Default TGIF Bump

Anyone else with info?
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Old 11-08-2002, 11:15 AM   #7
ChrisW
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sounds like you have a vaccum leak after the MAF sensor or with one of the vaccum lines.
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Old 11-08-2002, 11:50 AM   #8
Hank3
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After the MAF sensor meaning to the right of it when looking at the car from the front correct? I just want to make sure I'm doing everything correctly. Am I supposed to be able to hear a leak or should I just be looking for little gaps that haven't been closed with clamps?
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Old 11-10-2002, 01:11 PM   #9
Hank3
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Bump
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Old 11-10-2002, 01:59 PM   #10
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Hank:

There have been some isolated instances of MAF sensors going belly up, and some becoming contaminated with the overzealous oiling of oiled foam or gauze air filters.

Secondly, the fuel pressure regulator reference line occasionally pops off or is left off when screwing around with suff near the passenger side fuel rail. Also, if you've had the intercooler off, check those hoses for cracks or splits, proper tightening of the clamps, and correct engangement onto the next part.

Thirdly, if you have a Unichip, it might not have the correct correction multiplier programmed into it.
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Old 11-10-2002, 11:25 PM   #11
Hank3
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Gaspipe - thanks for the response. I'm banking on two of the theories you have mentioned. The MAF one or the Intercooler one. First off, there could've been a chance that my MAF sensor went bad since I had a Foam Filter (from my CAI) that was over-oiled. I tried cleaning the MAF Sensor with alcohol and Q-tips, but I don't know if that had any effect on it. If it did, then it was a $250 mistake If not, then I'm hoping it some sort of leak relating to the hoses around the I/C. I installed some Samcos a little while ago and installed and uninstalled an aftermarket BOV. I'm gonna look for any leaks in detail before I resort to buying a new MAF. Does this particular CEL coming on only at idle fit the description of a leak though? Will this particular CEL occur eventhough the leak(s) are occuring after the MAF sensor?
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Old 11-10-2002, 11:57 PM   #12
Gaspipe
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Hank:

The only time I have actually seen that particular CEL on a scanner was when my Unichip was FUBAR. When I was investigating that scenario, that's when the MAF sensor was suggested as a potential problem.

I don't have the voltage ranges for what you should see from the MAF sensor. You may want to seek another local wrx in that Tallahassee area and measure the MAF output with a multimeter and compare.
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Old 11-11-2002, 12:05 AM   #13
Hank3
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Default

So if the volts are the same between my MAF and the other MAF, should I assume that mine isn't bad?
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