Have you checked all intake clamps and vacuum lines and made sure none are disconnected or damaged? You mentioned the car is back to stock now? How many miles are on the car? What happens if you clear the code? does it come back on immediately?

 

Clamps all look good, can't see any hose problems.

I cleared the code, and within 15 miles of driving, the light came back on.

The bucking, hesitation, and rough idling seem to go from bad to worse to bad... It doesn't go away, but it seems to change how violent it is.

 

Well If your 100% sure the exhaust and intake system have no leaks and all lines look properly connected and not damaged I would prob be checking fuel pressure, the coolant temp sensor, and the intake air temp sensor..

 

Clean the MAF. Use a product specifically designed for a MAF sensor. Make sure it is cleaned very well, reconnected correctly, and that the air filter is clean and the filter cover is well seated on its tabs.

 

Very disspointed...

Subaru takes a look at the car, and tells me it is the exhaust air flow sensor. I argued stating I wouldn't think that sensor would make the car buck so violently, but they dismissed my thoughts and ordered the part - which means they keep the car overnight (evidently, Subaru dealers don't stock parts on hand).

I get the call today, and now they tell me that the MAF is ALSO bad - so I will have to wait until Monday to get my car back. While the MAF has a higher chance of being the culprit, I am still not convinced.

The worst part...... the loaner I got was a Prius.

 

Very disspointed...

Just a thought, since I've seen this CEL repeatedly:

Clean the MAF. Use a product specifically designed for a MAF sensor. Make sure it is cleaned very well, reconnected correctly, and that the air filter is clean and the filter cover is well seated on its tabs.

PO171 is a frustrating CEL since it seems to rarely reflect directly the cause of the issue. With your air filter setup I would not be surprised at all if a MAF cleaning would do the trick. I am not trying to second-guess your dealer -- mainly because I'm not near the car after all -- and what the dealer is planning is in fact likely to fix the problem, but I tend to start cheap and then escalate in costs when troubleshooting. Just IMO.

 

Got my car back... Seems like the MAF was the culprit. So far so good, but I have only driven 2 miles since I got it.

The highway ride home tonight will tell all...

After driving a Prius for the better part of a week, I am lovin the WRX.

 

i was looking for a aftermarket maf can anyone help me for 2002 wrx

 

Stop bumping posts. You have already posted a thread on this. Nobody makes an "aftermarket MAF". If you mean replacement Google would have your answer in like 10 seconds.............

 

ok i have the p0171 and cant find out what to do i when back to stock inatke/ clean maf/ injetor clean/ and looked over vacum hose. i need help i was having a hard time starting the car but fix that with injetor cleaner.now the car starts good and ilde rpm are back at 750 as at 500. so i as hoping that clean would fix everthing but after 60 km and 10 -15 start up the kight came back on. and i change the spark plug E3 (E3.64) but had the code before doing so

 

what side is bank 1 on a 2002 wrx. if you are sitting in the driver seat is bank one on the left or right side

 

There is only one bank. Bank 1 in this instance does not refer to a side of the motor.

 

i see well thanks

 

when you unplug the MAF and the car runs the map system dose the cyctem take information for the front anf rear o2 sensor to help decside how much gas to add?

 

Thats how they both work (MAF & MAP) in closed loop. Openloop does not use O2 sensor feedback. You might want to think about taking this car to a professional.............

 

So map is closed loop?

 

No..........both MAF and MAP use both closed and openloop fueling. At idle and part throttle you are in closed loop for best fuel economy and emissions. At W.O.T. you go into Openloop fueling. Difference with the Subaru is the ECU now thinks your MAF is broken and now is using the "limp" mapping for fueling and timing. You are technically in a lower state of tune when defauled to the MAP sensor. Google might help explain more about OP/CL fueling.........

 

I have a cobb port stage 1+ sf 93 Oct tune on my 2011 wrx hatchback. It has a cobb intake and I just put on a invidia n1 catback exhaust on it. I know for sure I have a exhaust leak where the downpipe meets the mid pipe...been driving it for a week a and BOOM all of a sudden p0171 code came up. My check engine light on and my cruse control light is blinking. Plz tell me it's just my exhaust leak that's making this happen.

 

I am driving a Subaru Impreza WRX 2002 2.0T EJ20 and I have the same code, car drives normally just the check engine light comes on and off, and fuel consumption is became crazy high. Tried the water test to check for leaks and couldnt find one. I know I came a bit too late

Please advice

 

Follow the instructions in the thread. Did you clean the MAF?

 

I did follow up and cleaned the MAF, just order a smoke machine to do a vacuum test

 

I know this is a old thread but this happened to me this morning thought last night that the code was due to my new dual port bpv but the intake tubing came off the box and was just chilling this morning sounded like complete shit when I started it turned it off drove the wife’s car came home subispeed package with oil change had came in when under the hood and found that lol