Sputtering down low, stalling, intermittent CEL

[Vincent Brick]

1991 325i 5-speed, engine has approx 250k and was fully resealed and had good compression upon installation 13 months / 15k miles ago.

All of a sudden a few minutes ago my CEL came on at a red light. It went off when I pulled away. Two red lights later I try to pull away and the car stalls. I then have to rev the shit out of it to make it not stall pulling away. Low speed through my neighborhood in 2nd and it sputters if I try to give it gas, makes no power. When operating the throttle from under the hood the engine seems to shake more than normal when revving it. Temp is normal, it has 3/4 tank of gas.

Any ideas? I have to get this fixed in time for my 80+ mile work/school commute tomorrow. I don't even know where to begin in troubleshooting such an issue.

Thanks.

[UlrichFennec]

Have you checked any codes with a stomp test?

[Vincent Brick]

You know, I meant to do that when I got home and spaced it, gonna go do it now. Headed to my buddy's shop in a little bit for a smoke test and general look-over, he works on E30s not every day but at least every week and he thinks its just a vac leak or bad AFM.

[Vincent Brick]

Code 1222 lambda Control 1.

I have a spare O2 if I need it. I have had 14# injectors in it since it was on its previous engine (2 people told me they would tune it for free then said they wouldn't bother since the gains would be so low) but they have never given me any previous issues so I don't think that is it.

My buddy will know what's up, I'd love to learn how to diagnose things better myself though.

[UlrichFennec]

That's most likely a bad O2 sensor or a vac leak. They'll hide in all sorts of places too. I had mine at the oil return tube upper, throttle body gasket and a couple injector o-rings. Just replaced every vac line and the O2 sensor and haven't had any problems since. Idle settled back down to 750-800 too.

Check your injectors and your temp sensor, if you wanna be thorough.

Good luck!

[Vincent Brick]

Drove over there and it wasn't messing up. Threw the smoker on it and no leaks. Fancy scanner said O2 out of range more than one start cycles prior, not-so-fancy mallet said my IAC was on the way out. I had a spare O2 sensor, the shop gave me a good IAC they had laying around, and now it runs great, noticeably better than it has been leading up to this, and it still may need another couple start cycles to learn the IAC I would imagine.

So yeah, good call on the O2. And you can get a lot more info out of these things with the big money scanners (I'm not sure this particular model, it was blue and had a large color touchscreen) than I was previously aware.