Hoping for someone to point me in the right direction

[broberge7]

First off, I'd like to say I'm sorry if this is in the wrong section. I'm hoping for someone to point me in the right direction. I have a 2005 Legacy GT 5EAT that's running Cobb OTS Stage 1 91 Oct., ever since I got the car when it was 100% stock the gas mileage has been horrendously bad. I get 12 MPG Driving in the city (Even when I drive like a grandpa). So far I have replaced all 4 spark plugs with some Bosch plugs, I've changed 2 of the injectors because of misfires on those 2 cylinders, I've changed all 4 coil packs and the front o2 sensor. I have checked all 4 rotors and I am 100% sure that none of them are seized or dragging or anything like that. One thing that I have noticed which is pretty weird is that my car stutters really bad when it's just creeping forward and my foot isn't on the gas, it literally almost feels like the car is going to stall out but it really only does this when it's cold. I'm not sure if that would be related to poor mileage or not but I'm pretty stumped here. I'm wondering if there is anybody out there who would know of anything I could monitor on the COBB AP that would help me get closer to finding out the source of this issue.

[Phillip J. Fry]

some say when cold the intake something or another o rings shrink up and cause vacuum issues etc.

 

the plugs you should have used are ngk iridiums. nothing more and nothing less.

 

its possible your 02 sensor isnt working well. but you said you replaced it. did you use stock parts? if you have an aftermarket bpv it could be sticking.

 

how is your highway mileage?

[broberge7]

some say when cold the intake something or another o rings shrink up and cause vacuum issues etc.

 

the plugs you should have used are ngk iridiums. nothing more and nothing less.

 

its possible your 02 sensor isnt working well. but you said you replaced it. did you use stock parts? if you have an aftermarket bpv it could be sticking.

 

how is your highway mileage?

 

Interesting on the plugs, I was reading about how those bosch plugs aren't the best for our cars just last night so I will definitely be changing those out for NGK Iridiums. Maybe it's possible that my rear O2 sensor is the one acting up, I only changed the front (OEM) but before I changed that my AF Ratio was off according to my accessport. But the numbers were back to normal after I had changed it and I got some drive-ability improvements and got maybe like 1 more MPG. I have the stock BPV, and I get about 18 MPG on the highway. I used to have really bad issues with the car misfiring which took me awhile to figure out. Ended up being Injectors #2 and #4 so I replaced those with OEM ones and that got rid of my hesitation, CEL and rough idle. I mean, maybe it's possible that the other 2 injectors are also leaky and need replacement but I'm not sure about that since I usually don't have any CELs, but just last week when I was heading home from work I had the car start bucking like crazy and I got a flashing check engine light and my car went into limp mode, I continued home and within 15 seconds the check engine light turned off and the car was completely back to normal. I went ahead a cleared the code and it hasn't come back since. That was quite weird but I'm thinking that may have either been some bad gas (the gas in my small Canadian town sucks) or it may have had to do with the bosch plugs. Either way I will be changing out all 4 plugs for NGK Iridiums once my downpipe and up-pipe come in from Cobb. Thanks for your suggestion!

[Phillip J. Fry]

Interesting on the plugs, I was reading about how those bosch plugs aren't the best for our cars just last night so I will definitely be changing those out for NGK Iridiums. Maybe it's possible that my rear O2 sensor is the one acting up, I only changed the front (OEM) but before I changed that my AF Ratio was off according to my accessport. But the numbers were back to normal after I had changed it and I got some drive-ability improvements and got maybe like 1 more MPG. I have the stock BPV, and I get about 18 MPG on the highway. I used to have really bad issues with the car misfiring which took me awhile to figure out. Ended up being Injectors #2 and #4 so I replaced those with OEM ones and that got rid of my hesitation, CEL and rough idle. I mean, maybe it's possible that the other 2 injectors are also leaky and need replacement but I'm not sure about that since I usually don't have any CELs, but just last week when I was heading home from work I had the car start bucking like crazy and I got a flashing check engine light and my car went into limp mode, I continued home and within 15 seconds the check engine light turned off and the car was completely back to normal. I went ahead a cleared the code and it hasn't come back since. That was quite weird but I'm thinking that may have either been some bad gas (the gas in my small Canadian town sucks) or it may have had to do with the bosch plugs. Either way I will be changing out all 4 plugs for NGK Iridiums once my downpipe and up-pipe come in from Cobb. Thanks for your suggestion!

 

some will ask if you have cleaned your maf sensor. that could be getting a little old as well.

 

last weekend my car bucked and went into limp mode for the first time ever. its still surging and is at a shop this moment to find why. when i know you will know.

 

are you hitting boost correctly? no leaks at the common places etc? some years ago an IC coupler gave me problems and boost peaked at 14 instead of 18 and i went through gas.

 

currently i can get 26+ on the highway even at times using some boost. 18 is very low. you have something going on but tough to say what. fwiw i had 0 codes when the boost leak was happening to me. i even hit fuel cut one time and 0 codes.

 

you need to test some things and do some datalogging.

[rapture]

Could it be tune related?

Any friends with a laptop and tactrix who can help take a look?

[broberge7]

some will ask if you have cleaned your maf sensor. that could be getting a little old as well.

 

last weekend my car bucked and went into limp mode for the first time ever. its still surging and is at a shop this moment to find why. when i know you will know.

 

are you hitting boost correctly? no leaks at the common places etc? some years ago an IC coupler gave me problems and boost peaked at 14 instead of 18 and i went through gas.

 

currently i can get 26+ on the highway even at times using some boost. 18 is very low. you have something going on but tough to say what. fwiw i had 0 codes when the boost leak was happening to me. i even hit fuel cut one time and 0 codes.

 

you need to test some things and do some datalogging.

 

Yes the car hits boost correctly and peaks at like 16 psi, when I had my misfiring issues I did in fact check for leaks and cleaned the MAF sensor. Maybe it's possible that the MAF sensor is on it's way out and just needs to be replaced? I'm just wondering what parameters I should log and what I should look for? I'm kinda new to the whole cobb accessport so I'm not sure how to use it effectively for diagnostic purposes. Thanks!

[broberge7]

Could it be tune related?

Any friends with a laptop and tactrix who can help take a look?

 

Anythings possible but I do not think it's tune related as the car got this bad mileage when it was bone stock as well. I'm not sure how to use a laptop to do datalogging, but I do have a cobb accessport. Unfortunatley I live in a small town and I am literally one of the only people who has a turbo subie here(Everyone drives pickup trucks) and there's no dynos or tuners within like 1000 km of me. Living in remote canada is terrible!

[Max Capacity]

Give my Tuner a email from his web site. http://www.tuningalliance.com Tell Mike I sent you.

 

He can walk you through the process of data logging and help get your car running well.

 

My wagon gets 23mpg around town and over 25mpg on the highway, its making a lot more HP then you are.

 

When my car was on Cobb stage 2 tune it would get over 26mpg on the highway.

 

If your car still has the block orings between the intake and TGV's, you'll want to install the new larger orange ones. Did that to my wagon back in 2011.

 

Where about in Canada are you ?

 

 

Oh, You might want to take a good light and look at the TB hose and make sure its tight on the TB and tmic outlet. May be look into a boost leak test.

 

I took a pint size paint can and plugged the hose off the air filter box, than pulled the small hose off the blow off valve, and give it a short blast of air from my compressor. then put your thumb over the hose, listen for leaks.