Sputtering under load

[I Like It Sideways]

This problem just came up today while I was driving my RS. I wasn't driving hard, nor for an extended period.

The engine began to cut out, wanting to die under load. If I pushed in the clutch and let it idle for a bit, it would be fine again for a few seconds, and then it would begin to sputter again. Then it began to idle really rough, between 400 and 500 rpm.

I've put about 30 miles on the car since I swapped in this engine.

Things of note: I have no cat, I am running EL headers, and a sawed off catback (stock catback with the muffler hacked off). The engine has been running super rich since I first started it up (I attribute this to an exhaust leak at the head, but that has been fixed since). Having as little backpressure as I have, this probably also contributes to the rich condition.

I reset the ECU, and it ran like a champ. So coil pack, plugs and wires are good.

This leads me to believe it is the front O2 sensor. Running as rich as the car has been running (backfires everytime I step off the throttle, and then get back on it), I just think the O2 sensor has been burned out.

Any ideas on what else it might be? I will be installing the Cobb catback that is sitting in my garage once I get the flange welded back on, so hopefully that will alleviate the situation.

[BlackParis]

Running super rich will make any car stumble bad in colder weather...


Did you drive it long enough to get into closed loop? Or was it just bogging in open loop?

[I Like It Sideways]

It was in closed loop. I let the car warm up for a good 10 minutes, and drove it for another 15.

[UP2MTNS]

fuel pump?

[I Like It Sideways]

fuel pump?

I thought it might have been, but after I reset the ECU, it ran fine

[kreitz3]

Maybe it just forgot what it was supposed to do. It has been a while.

[Qman]

O2 sensor for sure. Check the plugs to make sure they have a good connection. I have a bad connector and it forces it to go into limp mode.

[dome24]

Im having a similar issue on my EJ22 swap. I took a 700 mile road trip for tday and on the way back at cruising speed the car would just chug like it was out of fuel. only one chug then back to normal,It did this multiple times with no pattern, at least that i could tell. then today driving around at work it happend again at slow speeds and from a stop. Let the clutch out and nothing there, it would come back after a second or two but still really irritating.
Im gonna scan it tomorrow with my bosses tool.

EJ22 LongBlock
EJ18 Intake Manifold and injectors/wiring
Borla Headers
LGT Cats and back w/new 02's at swap time ~10k
1 yr old Fuel Pump/net and Under hood Filter

[dome24]

so after scanning mine it was a MAF low volt code, sprayed out the MAF and so far no stall

so far

[I Like It Sideways]

Interesting! Mine threw a low voltage O2 sensor (rear). So I'm not too worried about it. After fixing the exhaust, reseting the ECU again, the car runs perfect. Still rich, but with no cats, that'll happen :D

[dppaladino]

Theres a stickyed thread on RS25 in the troubleshooting section about hesitation and everything that can cause it.

[I Like It Sideways]

yeah, I saw that after I posted a thread over there too. :D

But I have that thread readily favorited in case that happens again

[dome24]

so i sprayed the maf, changed the fuel filter and no change, gonna change teh plugs tomorrw to subaru oem ones

[I Like It Sideways]

Yeah, OEM plugs and wires are the best to go with. I need to change both on my new engine

[dome24]

replaced the plugs, picked up a junkyard MAF still bogging every now and then, when i pulled my autolite platnums they were kinda white
http://i126.photobucket.com/albums/p113/dome24/Subaru/IMG00062.jpg
so i figured i was running lean. im wanting to swap in the injectors off my spare 2.2 manifold but i cant get them out of the rail, they spin but won't pull out. Ive tried prying up, sticking a flathead in the seam and prying but no go, just pissin me off more

:shootsself: