MAF sensor issues? Help.

Hi i'm brand new here but i'm looking for a second opinion and I'd really appreciate any feedback I can get from you guys.

 

So I recently purchased a 2005 legacy GT wagon in july, and for the last couple months it's been bucking. So in gears 1 and 2 under 3000 RPM's my car seems to hesitate or buck slightly when I accelerate. As of last night it's starting to hesitate in 3rd gear as well. It doesn't matter whether I hammer the accelerator or accelerate smoothly it will consistently buck/hesitate in gears 1 and two until I hit 3000 RPM's.

 

I brought it to my local chain garage and they suggested that it could be a MAF sensor issue but they weren't able to pull anything from the codes the car indicating an issue. I looked here and found that it could be dirty MAF sensor issue so I cleaned it twice and it still hasn't improved anything.

 

I'm at loss, do I need to replace the MAF sensor? Do I need to bring it into a Subaru dealership? Has anyone else had any experiences like this? Any feedback would be great, I appreciate anyone taking the time to read this. Thanks.

It could be any number of things, but, if there aren't any codes being thrown, then you're gonna have a harder time diagnosing what's wrong.

 

Hop into the regional forums for your area and find out where folks in your area take their cars (hint: NOT THE DEALERSHIP!) and give those guys a call to setup an appointment.

 

Welcome!

Thank you! I'm going to bring it to a mechanic and see if he can figure out what's going on.

I am actually having this exact issue, but I just replaced my maf sensor less than 1000 miles ago...

 

Mine is more at low loads but it's all under 3k rpm. I'm thinking my spark plugs might need changing...

First thing I would do is pull a Learning View from the ECU, maybe the previous owner may have modded the car and then put it back to stock without flashing the ECU back to stock........if that is the case.

 

My car did the same thing after I rebuilt my motor, the low RPMs were running on the lean side (causing hesitations), but the upper RPMs were on the rich side (running strong). Adjusted some of the fuel trims/timing on my current MAP, reflashed the ECU, and running good again.

 

To pull a learning view from your ECU, go into the "Tuning" section and read the stickies at the top, that will tell you how to do it with your own laptop.

I replaced my spark plugs about 300 km's ago and it's still doing it.

 

I bought it from the original owner who's probably in his late 40's with 3 kids, so I don't think he modded it at all. But I'll take a look at this learning view tomorrow. Thanks!

After doing some research I wonder if the car has an aftermarket front o2 sensor that it's not happy with, and if not possibly an oem one going bad.

It would be an OEM one, but thank you! I'll look around online for symptoms and see if it's similar to mine.

i had similar issues last year it was a bad front O2 sensor. u can get one at any local auto store. get the denso one

I thought most lgts had this issue. Mine has since day 1. Got a lot better after a tune

Most of the hesitation/surging issue get taken care of with a tune.. But since car was on factory tune for a long time, may have burnt the valves

Steps to be taken-

First pray to whatever deity you believe in that you wont be starting your own build thread soon, then

1. Vacuum gauge test- will tell you alot without too much effort

2. Boost leak test- check for leak where IM meets TGVs, Intercooler ends

3. Clean and/or replace OCVs

4. Compression and Leakdown test- tell if bad rings/lands or valves

then post here what you find and we will let you know

I'm no car wizard, so i'm bringing it to a mechanic. I'll let you guys know what he says.

X2 ^

I hope its a subaru mechanic or subaru specialty shop, not sure where you are from, you should post that and Im sure someone on here can point you to a reputable tech in your area

It's not a subaru dealership, but on WSC (western subaru club) everyone in my area seems to swear by this shop for it's quality and affordability. I originally brought it to my local chain garage to check the codes and they were pretty useless as to what could be wrong.

After making my post earlier in this thread, I have cursed myself. My car is now experiencing the same issue, and is going in/out of limp mode now. Going to swap the spark plugs and check for any vacumm leaks tonight.

You know what, my car has done the same thing, 05 LGT wagon too.

 

^ Totally subscribed to this thread. Let us know what you hear dude!

A quick update, the mechanic took the leggy out for a rip and believes the problem lies in the throttle body. So tomorrow they're going to take a look at it and I'll let you know.

So I got my car back today and the mechanic said there's not much he can do without codes. He said he would be wasting my money by trying everything to find out what's wrong. Like a needle in haystack. So until it gets worse there's nothing he can do.

Figured out my problem, while replacing the spark plugs I notice the air box was not fully closed on the bottom. Leaving an open gap about 1" and the filter was loose inside. After closing the air box fully, my car was running back to normal. Guess the filter was loose on the low RPMs causing the MAF to not calculate the aif flow properly. In return, causing the system to lean out until the turbo kicked in forcing the filter to close tightly. Which made it run smoothly after 3k RPM's.

 

Now with a closed air box, the car is running smoother than every, along with new plugs.