Cutting out under boost - 03 WRX

Pertinent info:
03 WRX - High miles, ots Cobb Stage 2 tune, catless up/down, GS EBCS. Plugs changed somewhat recently (August, I believe) w/ NGK platinum.

I know right off the bat that the ots tune is not the most desired thing in the world, but it's been running with no apparent problems for 3 years with it.

Anywho, I noticed today that the car is cutting out under boost all of a sudden, but not until it gets about halfway up the gauge (it's an oem Mpa one, so I'm estimating maybe 7-8 psi?).

The Google is telling me all sorts of different possibilities from coil packs, to plug gap, to vacuum leaks, to fuel pressure, etc.

Any suggestions on what to check first? Seems odd to me that it'd just kinda happen outta nowhere, or so I think. I drive pretty laid back for the most part so might not have noticed it immediately. That and all of the components seemed to have been working in harmony quite nicely as far as I can tell.

Thanks for any help.
-Cody

 

Start with all you listed. I've had iridium plugs go bad. Coil packs go bad too, you should notice laminations pealing or rusting. Also check your grounds (engine, battery, chassis) and connectors (map, iac, coils, harness by the battery). I've had a loose one confuse me for a while once or twice before.

 

I’ve seen ringland failure cause boost to cut too. So many things could cause it. Easy check to pop the oil cap while running and see if it’s blowing smoke.

 

if you keep it under a specific psi does it seem to pull fine?

 

I had something similar happen to me over the summer with my STi cutting out at 11 psi. Pulled over to check everything out and there was a vac line that had come loose. Re-connected it, zip tied it for security, and no problems since.

 

If it’s 10ish psi cut every time I’m pretty sure that’s wastegate pressure only and the computer is saying no more, something wrong here.

 

This can be a frustrating problem. I'm hoping its the plugs/coils. Those are usually the culprit and the easiest fix. If its not those, then you are wondering a bit.

Explain the symptoms more. Is it a stuttering and stumbling when you are hitting the boost? Does the car drive normal and will accelerate fine as long as your only boosting a bit? Is it EVERY TIME or just sometimes? How is your vacuum?

 

As far as I can tell, yes. If I drive "normal" without getting into boost it just seems like a normal car.

 

Yes to pretty much all of your questions. Spot on. I'd say every time, in 2nd, 3rd, and 4th gears for sure. Didn't really try to push the issue too much as I'm assuming whatever's happening in there isn't a good thing.

I did read something about checking the vacuum at idle. Any idea what I should be at on this stupid oem gauge? I can look up a conversion online, too.

 

You had to go and just throw out the worst one possible, didn't ya. Haha. Let's try to keep the bad juju to a minimum here.

 

You asked for easy checks for misfire symptoms. Haha. Check and see and go from there.

 

If it's a vacuum leak, your idle will likely be off or fast or "searching" for correct idle I would think. My money is on bad plugs/coils.

 

Sometimes the little clip that holds the electrical connector onto the coil pack breaks when removing them because they get so brittle... so then there's nothing securing the connector to the coil pack. It may have been fine for a while, but could have worked itself loose. Quick and easy to check that all the connectors to the coil packs are fully seated and secure.

 

Thanks to everyone so far. Looks like I got a busy night ahead of me combing through the engine bay. Hopefully I come up with more than these guys...

 

So took a few videos on my phone on the way home tonight to try and make it a little easier on the diagnosis side (for you guys). Unfortunately, the phone didn't really pick up the sound of the engine that well and the boost gauge is also a little misleading when comparing it to what I was feeling in the car. Anywho, I did let it ride out just slightly farther than any other time to kinda see what would happen (maybe a couple seconds). I ended up with a flashing CEL that went away after about 5 seconds. I was able to get my scan tool off the floor behind me and plugged in but just after the light stopped flashing. It did still pull a P0301 for me, tho, so at least I think I might have a spot to start from.

Light went out after the short flashing episode and didn't come back on. Another kinda weird thing is that the scan tool kinda restarted itself as if it lost connection to the car or something (I don't know, the tool itself was cold from being in the car permanently...). When it came back "online", it didn't read any codes and actually had a green light on for the first time ever with this car. This scan tool I has has green, yellow, and red lights, which light up based on the severity of whatever's going on (I believe). I've never seen it not be yellow at least, even after I've cleared codes. Who knows.

 

Sometimes the obd connectors can be finicky with connecting.

But I would try new plugs if you don't know the history and if that does not fix it buy a new coil pack or find someone with a used known good one and install it into cylinder 1.

Make sure the new plugs are gapped correctly too.

Check compression while your in there, quick and easy.

Also a boost/vacuum leak test. But likely a bad coil pack. With the newer subaru's you can see cylinder roughness and swap parts and see if it follows. With your car you need to swap a different known good part to test it. I'd say 90% chance a plug or coil pack.

 

On the bright side cyl 1 is easier to get to than 4! I have a working legacy coil pack or working sti one if needed for testing.

+1 on compression and checking gap. For sure on that cyl. Easy peasy.

 

Thanks for the offer! I'll let ya know if I need one.

 

I found out the hard way that these things are stupid picky about oem specific O2 sensors. Same thing with coil packs or will a decent quality aftermarket one suffice if I need to replace?

Certainly appreciate the help already!

 

Oem used will last longer then aftermarket when it comes to most parts. Coil packs are the same. Retail they are like $109 from the dealer. But the one that is bad (if that is the problem) is likely 15 years old! So always worth the money to go oem. If not new, then find someone with a good used one, but there are risks with that one too. Depends what your time is worth too.

 

$109 is without the mnsubaru discount at morries too. Got mine for $88 with the 20% off. Can’t go wrong there.

 

Thanks, gentlemen! Much appreciated.

 

So riddle me this. Drive to the store today and all is "fine" still. Go to leave and did one of those let the key go just before it starts things so had to try again. Started right up but had an active misfire. CEL flashing and definitely audible. Code reader came back with P0302 this time. Tried driving a little and it wasn't liking it (obviously), plus it smelled slightly gassy (not fart smell). So accelerate a little to get up the slight incline we were on so I could turn off at the next street. It barely hits boost but as soon as it did it cleared up the misfire and the light goes off... Returned back to running "fine" again.

So did my short burst of cranking but no fire cause the cylinder to flood out momentarily and it couldn't remedy itself without a blast of forced air?

Just filled up last night and got 24+ mpg the last tank, so now I'm even more confused. Where can I get some road flares I hear so much about on here?

 

Also, fwiw I do still have an AccessPort and could try to do some data logging if that would help. I've never done it before but wouldn't hurt to learn.

 

Got an early Christmas present this morning! Hooray...

Stepdad's got a pretty legit scan tool at home as he's an auto shop teacher at a high school. So I start the car to warm it up this morning and it seems to be running fine at idle. Go back out after a few minutes to read codes and the lights flashing at me again. Drove it around the block once and again when it hit boost for a second it's like there was a switch flipped and it instantly cleared itself. Only this time it came back again after about 10 seconds and then stayed there. Only code it pulled up this time was P0302 again. Below are some pics from the scan tool. While we were idling the car during the scan it seemed like it was again somewhat intermittent and would sometimes miss, sometimes clear itself. Sometimes the light would flash, sometimes would stop for a while. It did seem to smell awfully gassy again (assuming that one cylinder isn't firing and is just pumping that gas out the hole). Needless to say, we're not driving it home.

In his opinion, the B1S1 O2 sensor is reading funky. Coincidentally that's the one I replaced once already (with a used, working oem one). However, according to my Googling this morning it's not necessarily out of the ordinary to have higher readings on the front sensor. And since I know it's had a code specifically for that before, I'm assuming that if something was going on with it it would be telling me that instead.

Based on this info, anything else I'm missing here? I'll be honest I haven't messed with any of the coil packs and plugs yet as I figured I'd just wait til the holidays were over. I'm also kinda confused now as to why the code swapped sides (cyl 1 to cyl 2). Checking my back thread log the last time I had this #2 misfire was when the valves burnt. So that's cool.

 

It seems like this day is fast approaching.

 

Well, let the roasting commence...

Stepdad had a compression tester in the garage so I figured we'd give that a go quick before leaving because I'd at least have something to chew on for the week. Cylinder 2 came back with 120 so I didn't even bother with checking anymore. Plug in that hole was awfully dark, and yes, the gap was f**king ridiculous... Pulled #4 and it was also pretty big, but really white rather than dark.

Luckily for my ignorant a$$ O'Reilly's was open today. Ended up getting 4 new plugs and putting them in. Idle is pretty much mint now and my boost friend's back (and we're gonna get together!).

So I'll be taking this one on the chin and chalking up a life lesson.

 

Good deal. Cheap fix and I hope it is truly the fix.

 

Unfortunately I don't think I'm quite completely out of the woods yet (unlike Taylor Swift).

Car runs significantly better with the new plugs but still has a slight hesitation when in the upper end of boost, but not nearly as bad as before. So not sure if I should carry on down the coil pack route or what.

I came home to a Christmas "bonus" in the mailbox (if you haven't looked yourself up on the "missing money" website, I strongly suggest it. You never know...) so I might use it to pay the boys at JM a visit after this mess of a holiday season is over. Hopefully then I can at least get aimed down the right path.

Side note, below are some pics of the plugs I pulled out. My stepdad is claiming that all of them, other than cylinder 2, are running lean. According to the Google, I'm finding some conflicting results. Anybody care to explain?

#2 & #4



#3 & #1

 

Sooo is it fixed?

 

Not 100%. I'm hoping to have JM look at it when I get a chance to get it over there.

Edit - What I meant to say is, is it ever "fixed"?

 

Mine was running funny in the upper end of boost... I tightened the wastegate 1/2 turn seems fine now. I think the cold plays games with our old parts

 

Reviving this one to post the conclusion (I hate finding threads online that never have a result).

Anywho, finally broke down and took it to JM this week. He checked compression first (150-160 all around) and put in new iridium plugs. Still no better. Then started swapping coil packs around until finding some improvement. Apparently #3 was bad enough where swapping it out made a significant improvement.

Drove it home last night and it felt way smoother overall. Jesse suggested a proper tune as soon as possible so I'm hoping to replace all of the other coils before then just to be safe.

 

FWIW... My car did not like the OTS map with EBCS...went back to stock setup & stage 2 map till the pro tune

 

Cobb has a stage 2 with EBCS... I had fluctuation in higher than 14psi with it

 

Yeah, the Cobb website says the Stage 2 + EBCS tune is for a Cobb branded EBCS (of course). Mine is GrimmSpeed, but I figured they most likely do the same thing.

Either way, it's still not great so we're getting our ducks in a row here in order to get this tune that I've been talking about for years finally accomplished. Of course I'd love to put some more add-ons in before tune time to take full advantage of it, but I don't think that's gonna happen right now. However, the pro tune alone should make a noticeable difference over the OTS map, so maybe that'll tide me over for the summer.

 

Have you replaced your MAF sensor in the past X years?

 

Have not ever. I was actually considering that as well, but haven't called Subaru for that bad news (price) yet. Assuming it's another ridiculously expensive one (and probably has to be Subaru branded, like everything else apparently). I do clean it every time I'm in there, but it's also 15 years old like everything else.

 

Might want to pull the trigger, I think an OEM is around $100. I was just chatting with a very experienced tuner recently and he recommends it, says they can start to give erroneous readings after about 100k. Not bad enough to throw codes, but bad data that can affect the fueling calculations and make driveabilty suck.