Rich and lean craziness

[101]

Did you drain the old gas and put in fresh gas? If not - do that first.

Next, I'd start with the O2 sensor. Any time I've cleaned one I've just used heat and a wire brush - no chemicals. The gasoline you used may have fouled it.

As your car has been sitting a few years having the injectors cleaned would be a real good idea. They do develop deposits which can cause sticking and affect the spray pattern.

[SmilesPerHour]

I've got a spare set of injectors that I was gonna send away and have serviced and flow tested. The C191 plug was full of dielectric grease and looks fine thank god!

I've already changed the fuel hoses that looked cracked, the fuel feeder line as it was leaking when I bought it, and the FPR to be safe, as well as fuel filter. But it didn't solve anything.

The engine is getting too much air/ or too little fuel. I'm down to fuel pump, blue temp sensor, AFM, 02-sensor, or vacuum leaks.

I doubt it's the fuel pump, but haven't inspected it. I wouldn't expect these types of issues if it was failing though.

The blue temp sensor gave me the proper ohm-readings both when cold and hot when I measured from the ECU and seems to be working fine.

I switched in a known good AFM, but no difference. It actually runs "better" with the AFMs unplugged. Which makes the ECU go into fail safe mode and gives a rich fuel mixture.

I cannot find any vacuum leaks but I haven't checked the intake manifold gasket.

Since it switched from rich to lean after my stupid attempt of saving the old O2-sensor I'm leaning towards a faulty sensor. I'm not getting any CEL light or codes (Motronic 1.1).


What should I do first new Bosch O2-sensor or have the injectors serviced and tested?

[fenwick]

I'm in the exact same situation. But I can hear a misfire. I let it run and sprayed wd40 at injectors. New injectors and intake gasket on the way. Should fix it I'll let you know

Edit: I may just also need the o2 sensor

[SmilesPerHour]

Hello,

I have a 325i that had been sitting for a few years. I took it out and discovered I got sooty spark plugs and had a very dirty O2-sensor.

I changed the spark plugs and cleaned the 02 sensor in some gasoline and with a fine grit sand paper.

Now the car runs lean and chugs at high rpms, feels down on power, and it gets worse when the engine gets hot.

The plugs are super clean when I check them and I seem to have a fuel delivery issue.


All things being the same except for my stupid clean of the O2-sensor, could a faulty o2 sensor first cause rich running and then lean running?