Rich and lean craziness

[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?

[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]

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?

[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 emptied out all the old gasoline before I started working on the fuel system.

Alright, a new Bosch O2-sensor is ordered.

I'll report back in a week or two when I've got it installed.

[SmilesPerHour]

Okay, so I swapped in some known good injectors and a brand new Bosch O2-sensor. But the issues persists.

The engine feels utterly gutless when pushed. It revs slowly up to 5000rpm and cuts out. And then longer you drive that rev limit drops lower and lower. It cut out at 3500rpm after 10min driving.

I'm back to square 1.

Possible causes;

1) Problem is b/w the steering wheel and seat.
2) Bad crank position sensor (CPS)
3) Blocked catalytic converter
4) Broken rocker arm, valve spring, etc
5) Fuel pump relay
6) Injector loom connection
7) Throttle position sensor (TPS)
8) ECU

[SmilesPerHour]

Would a bad alternator cause these kind of problems?

[AndrewBird]

Not unless your battery was completely dead, but then you wouldn't be able to start it.

I would do a smoke test and check for vacuum leaks. Also pull your cap and rotor and check them out.

[SmilesPerHour]

Not unless your battery was completely dead, but then you wouldn't be able to start it.

I would do a smoke test and check for vacuum leaks. Also pull your cap and rotor and check them out.

I'm not sure how to do a smoke test but the intake boot and valve house vent hose are all new.

And if I unplug the vacuum hose from the fuel pressure regulator to intake manifold it sucks like crazy and the engine sounds like it's quite unhappy.

[packratbimmer]

Do a fuel delivery test per Bentley instructions. Basically measure fuel into a jar for a given duration. I can look it up if you do not have a manual. You might have good pressure, but not enough fuel.

[SmilesPerHour]

Do a fuel delivery test per Bentley instructions. Basically measure fuel into a jar for a given duration. I can look it up if you do not have a manual. You might have good pressure, but not enough fuel.

I followed the instructions in the bentley manual.

And when I switch the fuel pump on, I clearly hear a buzzing sound but nothing comes out into my container.

The fuel pressure regulator is new and the old one looked perfectly fine inside.

[packratbimmer]

Are you jumping the relay to actuate the pump? How long is is buzzing?

[SmilesPerHour]

Are you jumping the relay to actuate the pump? How long is is buzzing?

I built the jumping thing with the fuse and toggle switch. It buzzes for as long as the toggle switch it turned on.







I guess a new pump is in order?

[packratbimmer]

Yea - I had a bad pump that would work great until I got to wide open throttle. It just could not deliver the fuel. It finally went kaput at the post office one day.

[SmilesPerHour]

Thank you so much for the help!