Are you still using the stock fuel pump? Also who did the tune for your car?

 

I had a similar problem recently. Have you cleaned your IACV valve? Also I cleaned my MAF sensor which helped some but it ended up being completely bad. See if you can swap a friends sensor in and see how it runs. Fixed mine right up.

 

I have a 2002 WRX with 89,500 miles. It idles really rough at start up, sometimes stalling. The other day it cranked for about 10 seconds before it started. Idle speed fluctuates on startup. It will either rev up and down or rev up and then stay around 500 rpm sounding like its going to cut out. When the engine is revved is has some hesitation and also when taking off in first gear. It also feels like it hesitates when it enters boost. It also seems like it backfires once and a while and I notice a fluttering sound from the left side of the engine (exhaust gasket maybe). I replaced the plugs about 1000 miles ago with BKR7EIX (BKR7EIX-11 were in there) and also changed the fuel filter at the same time and cleaned the MAF sensor with the CRC spray. Hesitation got better but now its worse that it was to begin with. I also notice white smoke from the exhaust, could be condensation but I never noticed it before. It did have a misfire on all cylinders and was running rich but it went away when the UTEC switch was set to 1 instead of 0. I had no clue at the time what it was. The P0126 O2 Sensor code went away when I changed the plugs because of removing the battery and hasn't come back since. I also had a random misfire on cyl. 3 and switched coil packs. I also tightened all intercooler and intake clamps with no change. Here are the mods and codes my car has now. Any ideas? Can a bad fuel pump cause these codes and symptoms?

TurboXS FMIC
VF34 Turbo
Bigger injectors
Invidia DP and Borla catback
GReddy Headers and Uppipe
GReddy Turbo Timer
Manual Boost Controller
UTEC (Old Version)
Short ram intake

P0447 EVAP Open Circuit
P0171 Lean bank 1
P0301 Misfire 1
P0302 Misfire 2
P0303 Misfire 3
P0304 Misfire 4
P0447 Pending

did you tune?

 

No I have not cleaned the IACV valve. All parts were on when I bought the car. I also don't know anyone else who has a WRX so I couldn't swap MAF sensors.

 

I would first explore your Fuel pump. They are not that expensive and you should be using something high flow anyways.

Are you sure you are running the correct map? And the correct gas?

With all the fluttering and MBC's and FMIC and misfiring and back firing it sounds like you need a serious tune.

How is your turbo function? If I had to guess I am going to say it is a bit "Choppy" and somewhere around 3000 - 3500 RPM your car bogs down a bit and possibly backfires.

The "fluttering" could be your wastegate having a heart attack since your MBC is taking all of the work.

where did you get this car from? how different was the elevation between where it was and where it is?

 

It has to be the correct map because when it was set to 1, the rich condition and misfire on all 4 went away. I never heard any pinging and I run premium which is 93 octane around here. The fluttering comes from the drivers side of the engine bay. Hesitation does seem to start around 3,000 to 3,500 rpm when boost starts to come on hard. It seems to bog down then. I got the car from a dealer near the WI-IL border. It was previously an Illinois car. Elevation change probably not more than 1000 ft at most. I did a compression test today just to make sure everything was good there. I did each cylinder twice. I started on the passenger side and by the time I got to cylinders 2 and 4, the engine was pretty much cold. I'm not sure how much that would effect the results. There were problems getting the long adapter out. I couldn't get a socket on it. The plugs seemed a bit on the loose side for some reason.

Cylinder 1 155-153
Cylinder 2 157-157
Cylinder 3 150-150
Cylinder 4 147-149

 

I cant say for sure but the map could have been tuned for 91 octane, now I don't know if that would cause all of the misfiring maybe someone else could answer that.

If your getting hesitation when the turbo is kicking on it sounds like it is happening between open and closed loop. This could be a timing issue. When mine was doing that same thing it ended up being a combination of timing, injector scale, and MAF voltage. we just tuned through them so it felt worse then it was.

Although that isn't a huge elevation change it could be enough. Air density is also a factor. And MBC's don't like change. especially atmospheric pressure. This will change how rich and lean you are running also how much PSI your pushing.

 

Could it cause hard starting, rough idle and stalling during startup? I am also experiencing those. I also ordered a Walbro 255 in case thats the problem. The problem got worse last week but I had been running the same map most of the time. Idle at startup is best when the map is set to 0 which is stock.

 

Yep, if your running too lean you are getting too much air and not enough gas, could be related to the fuel pump, fuel filter, injectors, or an overall bad tune, (incorrect octane, etc. etc.)

That will cause rough idle, hard starting, stalling, back firing and more.

I would change out the fuel pump, and look into a tune. Your getting lean readings so I'm guessing you are in a lower elevation then where the car was from originally?

I cant say I know much about the UTEC but the idea is the same as my AP. 0 would be your stock 1 being your tune. Since the start up changes when you set it to stock then really all of your problems "could be" tune related.

These cars i tell ya

 

Honestly, with all those mods, I would take the car to a professional tuner that knows about subarus. Trust me, you have way too many mods and anything could be the problem. Take it to a pro before it is too late. If you are running lean that is the worst thing other than running with no oil that you can do to your car.

Sounds like the car needs a serious tune, as was stated before.

 

I don't believe it has a lightweight flywheel. Would one set a misfire code? I don't think elevation has much to do with it. Where I live elevation is about 780 feet and depending on which city it was located in prior, elevation is anywhere from 500 - 850 feet. When I get the new pump I'll throw it in and see if there's any change. I live in the metro Milwaukee area. Are there any tuners in the Milwaukee area otherwise I'd drive to Chicago if there are any good tuners on the cheap that anyone would recommend.

 

A flywheel lighter than about 13.5 pounds would indeed throw misfire codes. Especially when run with a lightened crank pulley.

Could the fluttering sound perhaps be wastegate flutter?

 

Would a lightened flywheel throw a constant or intermittent misfire code? The fluttering is coming from the drivers side, not the passenger side and the noise increases with rpm, not boost. Maybe an exhaust manifold gasket but I checked the bolts and they all seemed tight. Do Subaru's need valve adjustments often?

 

I bought a new 255lph Walbro and finally installed it today. Startup and idle are much better but I still noticed hesitation and backfiring when I took it for a test drive. I think I am going to take it to a tuner. I've been looking around on this forum and other places and heard about 555 Motorsports. They seem to have the best rates and are about two hours away from me. Does anyone have any experience that they would recommend them?

 

What happened to be the problem? I am having similar issues. I'm running a P0171 code. Cleaned MAF sensor and 02 sensor and air filter. Reset then 100 mi later the light can back on. Now I have white smoke coming from the exhaust.

 

I'd suggest starting your own thread. This one is 4 years old, and the OP hasn't posted since.

Make a new thread describing your problem with full details about your car.