Lean with Missfire's

[Mason Johnson]

Hello, I have a 2004 wrx that currently has a missfire on all 4 cylinders along with a lean code. I don't have the codes atm but will add them to the post later. Wanted to see some possible suggestions as to what could be wrong. Thanks!

 

[Eagleye]

Does the car have any modifications, if so what? Did you buy the car with mods or do them during your ownership? Is there an aftermarket tune on the car currently? Are you running an Accessport or Open Source program to see any data other than the codes?

 

[Mason Johnson]

The only modifications that are on the car that I'm aware of as I just got the car last Monday is an intake and a turbo back exhaust. Car is on a stage 2 tune on 93 with a COBB AP. The tune is also a COBB tune. I'd like to say AFR is a little high at idle. Floats around 18-20 but I also don't know if that's good or bad. First turbo subaru trying to learn the car as I progress. Car idle's at 500-600rpms. And before you ask, I didn't pay a lot for the car so I'm not to worried about what could be on that's aftermarket. To me the car looks bone stock other than the above modifications. Car is pushing 15 PSI. Invidia down pipe with HKS catback exhaust.

 

[Eagleye]

Several issues are jumping out given wheat you are saying.
1. Off the shelf Stage 2 Cobb Tune on those mods is not going to be good. The Cobb map is designed for use with Cobb's Intake and Downpipe. Other models use differing designs that can greatly change fueling requirements.
2. 18-20 AFR is way high. 14.5-15 is where you should see it floating at idle. Down around 11 at WOT IIRC.
3. Saying you aren't worried about what is on it aftermarket is a bit strange to me. I would want to know what is on a car I am buying so I know if anything needs to be checked out with the tune prior to getting into boost. It may also tell you what could be going on.

With all that said I would check the usual stuff: look for boost/vacuum leaks, exhaust leaks, pull a spark plug, and reflash the map. Beyond that I would log a couple of pulls and post the info on here. There are of course other things to look at but I wouldn't get too carried away until you check for leaks and reflash.

 

[Batmobile_Engage]

Before you do anything else, carefully remove and clean (with an aerosol MAF cleaner) your MAF. If it's not reading properly, we'll never figure this out. It's probably fine, but it's something we should try to rule out of the equation early on.

Sometimes, idle AFR measurements aren't very accurate. But if your AFR reporting is still off, when on throttle, I would be concerned. Otherwise, I agree with the above; 14.5ish at idle, 11ish at WOT.

What intake is on the car? I'd be willing to bet that is the primary culprit in this problem.

 

[Eagleye]

Before you do anything else, carefully remove and clean (with an aerosol MAF cleaner) your MAF. If it's not reading properly, we'll never figure this out. It's probably fine, but it's something we should try to rule out of the equation early on.

Sometimes, idle AFR measurements aren't very accurate. But if your AFR reporting is still off, when on throttle, I would be concerned. Otherwise, I agree with the above; 14.5ish at idle, 11ish at WOT.

What intake is on the car? I'd be willing to bet that is the primary culprit in this problem.

Agreed

 

[Mason Johnson]

Reason I'm not to worried is the car has 226k miles on the car. The intake is a K & N Typhoon intake system. Now that I know it makes sense. Is there any other type of off the shelf tunes I can use or do I need to just go to a base map tune and then get a protune?

 

[Mason Johnson]

Should I use a stage 1 map as it doesn't require a COBB turbo back. Or should I just run a base map due to the K & N intake? Car has a stock turbo so I'm assuming it's a normal waste gate. Car has no other modifications from what I can tell.

 

[Batmobile_Engage]

If you're running a Cobb OTS tune with those mods, I'd probably run one of the Stage II tunes. Heck, maybe even one of the low(er) boost, 91 octane tunes. Then of course, fill it with 93 for safety's sake until you can get it protuned on a dyno.

At 226k miles, anything could be wrong, but if I had to bet I would say that the tune is does not take into consideration that intake. Thus, the MAF is not scaled properly to accurately read the increase in air and you end up running too lean.

 

[Mason Johnson]

So should I put on the stage 2 tune and data log then and see what happens? I'm assuming the only way to fix the issue is to get the cobb intake system.

 

[Batmobile_Engage]

You don't by chance have a factory intake laying around, do you? I hate to have you buying performance parts for a car with that many miles on it.

I'm not too familiar with Cobb's more recent tunes, but from what I recall, the tunes for GD era Subies don't factor in an aftermarket intake. They are designed for use with a Cobb downpipe alone. Part of this is because the factory intake supports 400whp as it is, so there's not a lot of reason to replace it early on.

If you don't change the intake (or anything else for that matter), you'll definitely want a protune. Call around a talk to some tuners before you just show up. Lots of tuners will refuse dyno sessions on older vehicles because they are afraid they will blow up and they'll incur some blame or cost.

But to answer your question, yes. We can kick around some ideas on different off the shelf tunes if that's how you want to go, and you can log the results. I'm not very tuning savvy, so maybe Eagleye can look them over for you.

Theorizing here (so don't blow your engine up and get mad at me), if you are running lean, I'd think you could start with this map:

https://www.cobbtuning.com/maps/2004-subaru-impreza-wrx-stage-2-map

...and set it to: FUEL TYPE: ACN91/CAD94 and WASTEGATE: LOW WASTEGATE

Then of course, you fill it up with 93 octane.

This *should* push things back in the right direction, via a reduction in boost and timing. If anything, it's probably safer than the tune on it now.

Sanity check that for me [MENTION=692]Eagleye[/MENTION] ^^^

 

[Mason Johnson]

I do not. I received the car with these parts on it and its my first. I at least want to get rid of the miss for the time being. That being said should I try the base stage 2 tune or..?

 

[Batmobile_Engage]

Read up, I edited my last reply.

 

[Eagleye]

I think a reflash is in order anyway, so I'm with [MENTION=662]Batmobile_Engage[/MENTION] on his suggestions. I would consider trying to trade for a stock intake if you can. You will see lower intake temps and it should improve your AFR.

 

[Mason Johnson]

Sounds good. I'll see if I can make it happen. I have parts to a cobb intake system but don't know if I can use an aftermarket filter or not. I'll do some data logging tonight. If someone could explain the process of how to download the tunes and get the logs that'd be great. Or at least send me to a page where I can learn how.

 

[Mason Johnson]

Alright just got done data logging. Car is running a little better on the new tune but im still seeing AFR's from 11-25. Idle has also become a little better at times. Kinda like the car catches itself but then forgets and idles rough again. Let me know how'd you like to get the info [MENTION=692]Eagleye[/MENTION].

 

[Batmobile_Engage]

If you have a Cobb intake laying around, throw that on for sure. The filter itself doesn't make any difference tune-wise. So you could go find a K&N cone filter that would fit or an AEM dry cone filter, etc. Most auto parts stores will have something that will work.

Stock intake is best, but Cobb intake is a close second.

You're running that 91 octance low wastegate tune now?

Sent from my SM-G925V using Tapatalk

 

[Mason Johnson]

Alright I'll try that this weekend. Yes car is now tuned for 91 on a low wastegate. Car preforms better than on the last tune but still having idle issues. Definitely a step in the right direction.

 

[Batmobile_Engage]

Great! I'm glad to hear that things seem to be working a little bit better. Of course, to be clear, this is just a temporary bandaid. I hope no one else reading this gets any crazy ideas about running this kind of thing long term. :lol:

 

[Mason Johnson]

I almost think its an injector issue. The car will idle perfectly fine at times and then it just bumps up to 20 on the AFR. I feel like the car shouldn't have a miss with the lean code I'm still getting in the car. Maybe timing? I just some highway pulls while data logging, just need someone to look it over now.