CHANGED SPARK PLGS CAR THROWING CODES?

Tiny
HOOKIE
  • MEMBER
  • 2008 BMW 328
  • 2.0L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 110,000 MILES
Hello I changed ^ bmw spark plugs but think they were aftermarket. The car misfired all over the place till I regapped the bmw spark plugs. #6 coil was very hard to pull off.I hope I did not crack the valve cover.

now the car is throwing a maf sensor codes and 2 lean codes bank 1 and bank 2? Both cyliners (all) running lean 29e) and I think it was 2901
please help
Sunday, January 4th, 2026 AT 9:21 AM

6 Replies

Tiny
HOOKIE
  • MEMBER
  • 99 POSTS
  • 2008 BMW 328
  • 2.0L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 110,000 MILES
Hello I put in bmw spark plugs and I think they were aftermarket. They misfired like crazy till I fixed the gap.I did not touch the maf sensor.I havd trouble pulling the coil off cylinder # 6 I hope it did not crack anything on valve cover.

Now I get 2 lean codes. Bank one and bank 2 and a maf sensor code?

29e0 and I think its 29e1 both are for bank #1 and bank #2 and the other code is for MAF sensor.I cleaned the sensor and codes still on car. PLEASE HELP
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Monday, January 5th, 2026 AT 9:17 AM (Merged)
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,494 POSTS
So you will get these codes because the engine is misfiring, I would remove the spark plugs and check them for cracks which is common when installing hard to get to spark plugs/

2D9E / 2D9F (very commonly misread as 29E0 / 29E1) OR sometimes shown as:

29E0 - Mixture control, bank 1
29E1 - Mixture control, bank 2

These are lean condition faults, meaning the engine is adding fuel but still can’t correct the air/fuel ratio.

Also, it is advised to replace the ignition coils as well, they have a high failure rate. Also, I would install either

NGK ILZFR6D11 or Bosch ZGR6STE2 gapped at.044 if they look off, most of the time they come pre-gapped so no adjustment is necessary. Clear the code once completed. Please upload a short video in your response of the problem, so I can see what's going on

Ken
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Monday, January 5th, 2026 AT 10:32 AM
Tiny
HOOKIE
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HI KEN thank u very very much for ur reply. Please answer the following questions
1. The car was throwing MISFIRE codes when I first installed spark plugs. They were not gapped, now that I regapped them, why dont they still throw any MISFIRE CODES instead of both banks being lean codes?
2. Also, I did not see any cracks in the plugs they are set at.040. Is that too NARROW of a GAP?
3. ALL coils are new except oone has some black rubber missing off of the side of it. Will this cause MISFIRES?
4. The engine runs fine at high speeds. Weird.
5. I dont have a smoke machine so any more advice MUCH appreciated.

ALSO why is it throwing a MAF CODE? I cant download a video. So sorry GAIL
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Tuesday, January 6th, 2026 AT 1:59 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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Sometimes it takes awhile to trigger the misfire codes from the computer, the gap should be.044, the codes must be in good shape which it sound like one is not so I would replace that one with the rubber missing. For the MAF code it could be you need a new MAF sensor or the electrical connector is not seated completely or you have a leak between the sensor and the throttle body, so I would check those first before replacing the sensor. Clean the codes once the repairs are made and recheck please, Ken
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Wednesday, January 7th, 2026 AT 11:40 AM
Tiny
HOOKIE
  • MEMBER
  • 99 POSTS
HI KEN thank u very much for your help. So should I REGAP all the spark plugs? They are at.040 and not.044. The second thing is my oil filter housing GASKET is leaking. Will that throw lean codes too. AND if I dont have the plugs torqued down tight enough, can that also throw the lean codes?

I am going to replace the bad coil with missing rubber insilation. Should I also but new plugs? I think these are AFTERmarket bmw PLUGS. THANKS
gail
oh ONE OTHER THING MY maf SENSSOR HAS THREE CONNECTORS ON ONE SIDE AND 4 ON THE OTHER SIDE. IS THAT NORMAL?
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Friday, January 9th, 2026 AT 8:12 PM
Tiny
KEN L
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So a misfire will create the lean codes, So we need to fix that first and then clear the codes here is a guide to help give you more information on lean conditions.

https://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers

Also, this video will show you how to look for vacuum leaks.

https://www.youtube.com/watch?v=LRKWV4Are5c

and

https://www.youtube.com/watch?v=xN5pcM-5bso

So the MAF sensor should have 4 wires on the sensor and electrical connector. Can you upload an image? also, does this car have a 3.0 liter engine?

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Saturday, January 10th, 2026 AT 9:27 AM

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