MAF, O2 and Transmission
 

OK, so i was doing some research and found out that a bad MAF can cause some hard shifting in the transmission. (i just got my transmission rebuilt 10K ago and it sporadically downshifts hard.) basically what i found was that if the MAF is giving bad info it can effect the engine RPM and computer and give bad shift signals to the trans. sounds logical. what do you guys think?

i have 105K on my 2002 4.4i, recently some rough idle, and plan to do the following. (hoping to fix issues and restore some performance)

NEW MAF
New Pre CAT O2 sensors. forget the post CAT O2s as they only tell the computer that the CATs are working.

is my thinking correct?

also, ream OEM does not show a part number for the pre and post O2 sensors. bavAuto and other sites show them as different parts. i'm sure i can find the right part number searching here, which i will do. if you know them please post here.

I was planning to do all O2s but now you got me thinking to replace only Precats. and get used post cat so computer has no errors.

from what i know, the post cats just report that the CATs are working... therefore if they are not failed and work there will be no performance change, pre CAT O2s however...

pre-CAT (up stream) Oxygen Sensors by BOSCH
Part Number: 13477
Alternate Part Number: 13802

post-CAT (down stream)
Part Number: 15109

BOSCH MAF
Part Number: 0280217814 (BOSCH Part 0 280 217 814, BMW Part 13 62 1 433 567)

i'll post any improvement. (will also be cleaning my intake filter.)

Good luck, Keep us posted

ok, so i after a week or so i have noticed that my MPG went up, car runs better and the throttle response is better. The trans still acts up occasionally, especially on down shifting. (and more noticeable when slowing on the highway to 2 and 1 gear after its warmed up) i thought at first it shifted better but it's hard to tell.

i would have to say that maybe i have a problem with trans cooling, or some of the sensors in there are acting up. i will have to go back to AAMCO and see what they want to do. i was hoping that i wouldn't have any trans issues since my rebuild 10K miles ago. (105K on the odometer and counting.)

Good news that is. O2s are on my list now. I get the same feeling occasionally also and I just got my rebuild for tranny. Got to find out what it is.

RealOEM.com * BMW E53 X5 3.0i Lambda Probe Fixings
lik to the o2 sensor . they are called LAMBDA PROBE (pre cut ) and Lambda Monitor sensor (post cut)

and they are for?? they are in addition to O2 or something? never heard of it.

they are o2 sensors . BMW has a different name for them it calls them Lambda sensors