2005 M3 === Request Help with Rough Running Engine

[riderosa]

2005 E46 M3 (6 SP) 110K miles

After the car warms up I am getting codes 171 and 175. When the car is hot is when the engine runs rough, If I shut off the engine and turn it on it seems to run fine again. The history is that I installed AA headers with pre cats only (new), replaced plugs, replaced coil packs, new intake boot , and new factory MAF sensor. I have verified that the pre cat O2 sensors are in the correct location on the headers.
I should also mention that the ECU was sent to AA for an update after the header changes.

[Fresh1179]

Is it a rough idle? Did this only occur after your ECU flash? I would start by cleaning the ICV valve with some throttle body cleaner and check the surrounding vacuum lines while you are in there. I had the exact same issue with my 110k S54. The next step would be to replace/clean the injectors and make he fuel pump if you are experiencing surging. Finally, if she new to you I would do a valve adjustment and simultaneous Beisan treatment. Reset adaptations.

Edit: I would also clean the throttle bodies and check throttle linkage for freedom of movement when the air box is off for the ICV valve.

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[Tbonem3]

I think 171 is SAP and 175 is oxygen sensor for bank 2 (cly 3-6).

Maybe you didn't plug SAP in or you deleted it, but it wasn't addressed in the tune?

Double check O2 locations/connections.

[riderosa]

The problem manifests after the car has run for awhile and I bring the revs up to 5000 rpm. At that point the engine stumbles and I have to shut it off and restart it. I am thinking it may be the injectors but it revs freely when the engine is not fully warmed up.

[Arith2]

Look at the voltages of the O2s when this is happening. Compare them. Also the SAP should not be throwing any codes with AA if you decided to spend the extra $50 or whatever. You don't need INPA to see voltage.

[riderosa]

I only have the pre cat O2 sensors. Should they both be approximately the same voltage?

[Arith2]

I only have the pre cat O2 sensors. Should they both be approximately the same voltage?

Yes. Around .4 to .5

[riderosa]

If the left and right bank pre cat 02 sensors are swapped would that cause the engine to stumble when in CL (fully warmed) condition?

[Tbonem3]

Yes, check your locations. That is the main problem people have. The connectors are color/shape specific, so that's harder to mess up. The actual sensor end is all the same between the 4, so easier to misplace.

[riderosa]

I will try his since it is easy and I have nothing to loose. Not sure I fully appreciate why there are 2 banks for the pre cat.

[Tbonem3]

bank 1 cyl 1-3, bank 2 cyl 4-6 that's both for pre cat and post cat, so 4 total. Left and right, more resolution than a single.

[riderosa]

Quick follow up............I had the precat 1 and precat 2 swapped. When I corrected this the car is working fine again.

[lemoose]

Quick follow up............I had the precat 1 and precat 2 swapped. When I corrected this the car is working fine again.

Lmao this seems to happen to everyone (myself included) even though we swear up and down we couldntve swapped them

[jet_dogg]

I love when people come back and update threads for closure to help others who may come across these issues.

[peterr991]

Great that you solved a problem. In mine bmw recently broke the timing chain, so I had to buy the whole new engine https://orbimotors.com/ because it was not worth repairing :/