1998 e36 323is, about 130,000 miles, check engine light is on. No starting or running problems, but it seems to be running rich.

I pulled the codes:

P1250 Mfr Ctrlled Fuel And Air Mixture
P0170 Bank 1 Fuel Trim Malf
P1188 Mfr Ctrlled Fuel And Air Mixture
P0101 MAF/VAF Circuit Range/Perf Problem

After I cleared the codes, these were pending:

P0170 Bank 1 Fuel Trim Malf
P1188 Mfr Ctrlled Fuel And Air Mixture

Using the stock air filter (no oil). I felt the hoses that attach to the intake and found no holes. So I'm thinking I have a bad pre-cat O2 sensor.

Does that seem likely? Any other ideas?

I have access to a Gensys scan tool. Does anyone know of a reading that would indicate the O2 sensor or MAF is bad?

Steve

Bump.

Anyone have an opinion?

At 130k you are 30k past the point that the pre-cat O2 sensors should have been changed. Changing those should be a top priority, but that may not be all thats wrong. The car is old enough that an intake leak from a bad hose or a failing CCV is likely A crankcase pressure check will tell if the CCV has failed and a visual inspection or spraying carb cleaner will find many intake leaks. A smoke test of intake will find any intake leak other than a failed CCV.

Thanks, Jim.

I plan on replacing the O2 pre cat sensor this week. I'll look for leaks and spray some carb cleaner for leaks while I'm at it.

I replaced the clutch and flywheel last year. I had the intake manifold off then to access the starter. The hoses looked fine then, but the car sits outside and a leak could have developed. I'll see if I can figure out how to check the CCV.

Steve, did you fix the problem?
I got the code P1250 yesterday and have been
trying to figure out what it is but the code
is generic and not BMW specific. Mine doesn't
have stalling issue or running issues. It runs like
champ but after a whole little shaking going on in the engine,
the car threw the code along with misfiring cylinder code.

Well, I replaced the oxygen sensor. That sort of fixed the problem. I also checked and found no leaks.

But after resetting the codes, the P1188 code returned. That surprised me, because that was the code that I thought was directly caused by a bad O2 sensor. I will say that the car ran much smoother and seemed to have more power.

After that my son had to drive the car back to college, so I couldn't do further diagnosis. I plan to do a bit more work on it when he returns for Spring break. I suspect the CCV or one of the hoses might be the problem.

I looked in my e39 5 series Bentley manual and I can't find a P1250 code. I guess it could be specific to 3 series, but I sort of doubt it. Most online code tables don't list it, either. The only thing I found was "Fuel level too low". I have no idea what that's supposed to mean. About as far as I can get is
P=pwertrain
1=BMW specific
2=fuel injection
50= some component.

Anyway, if you know you have a misfire, fix that and hope that the P1250 goes away.