Rough idle and vibrates when gear engaged in D or R

Tiny
BIGGIEG55
  • MEMBER
  • 1998 BMW 318I
  • 1.8L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 145,000 MILES
It has even stopped sounding the reverse bell and the reverse light have also stopped. The power has been lost even just on the very small sand it gets stack but in the tar mark it just move fine. But again I am not sure if the gears change but when it gains speed it just moves fine. I don't know what the problem is but my mechanic says it is the air mass sensor which he demonstrates by pulling off the cable but again without the air mass connected it switches off when gear is engaged in D or R. But how can the air mass has something to do with the reverse lights? Can someone please help me? Because the car was even put on the diagnostic machine and it only showed the air mass according to the mechanic. Help me please!
Sunday, October 13th, 2019 AT 9:25 AM

1 Reply

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,127 POSTS
Welcome to 2CarPros.

What code was retrieved? Also, the back up lights and the reverse bell, it sounds like the reverse light switch has failed, and it has nothing to do with the mass air flow sensor. I attached a wiring schematic below. Note that I broke it into three pics so you could read it. I did, however, overlap it so it is easier to follow.

Take a look at the pics. You will see power is provided via fuse 26 in the power distribution box under the hood. It then goes to the reverse light switch. Once the switch is closed, power travels to the back up lights and to the chime module.

Power is supplied via the same fuse to the transmission range sensor and that appears to be working, so I don't suspect a fuse. It could be the bulbs, but if that was the case, I feel the chime would still alarm. First, make sure the bulbs are good. If they are, check the switch for adjustment. If it is properly adjusted and still not working, replace the switch.

As far as the rough idle, if you could provide the code, it would help me.

Let me know if this helps or if you have other questions.

Take care,
Joe
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Monday, October 14th, 2019 AT 7:23 PM

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