Car lurches intermittently when A/T shifts - BMW Forum -
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#1 (permalink) Old 10-30-2005, 01:53 PM
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Car lurches intermittently when A/T shifts

hey folks i'm so frustrated

My 94 325is lurches intermittently when a/t shifts, it's like my car is hit from rear boom! on shiftup & shiftdown on 'D' position.

If this comes constantly I would say A/T is messed up. But it comes 7 out of 10 attempts. I mean, it's unpredictable. If once a/t shifts good on 'D' position, car never lurches while driving on 'D'. But if I move gear selection knob to 'P' and 'D' and restart as I stop by shopping mall and restart, car lurches on shifting point.

It never lurches on 1 or 2 or 3 position. it comes only on 'D'.
So if this happens, I put it on '3' until I get to stop signal and then I repeat slide the knob P <-> 1 more than 5 times. On green lights, if shifting's good I keep crusing or repeat it at each signal until it shifts good.

here is the list i've been through.

1.ran diagnosis - i got a code for bad knock sensors

2.while I replaced knock sensors, I replaced ICV alternator hoses lines sealing rings filters, new throttle body unit.

3.changed transmission fluid twice with new filter & gaskets.(it never leaks)

4.restored stock dme chip & tcu chip from dinan chip sets.

5.replaced DME & TCU whole units with same s/n oem ones.

I've been wasting too much money & time but nothing's improved used:
I wonder if there's any automatic transmission position sensor or something.

bcuz after several attempts of sliding tranny knob 'P <-> 1' , at a certain point it shifts good and at certain point it lurches. So I doubt any kinda tranny gear position sensor.

The weird thing is i've never had '!' on dash even though I've checked the bulb is working good. And It never gave me 'check engine light' yet.

I've used to have some old a/t cars and when their tranny started slamming, they 'always' slammed to shift. I'd say my bimmer doesn't always do the same slamming. I mean, it intermittently lurches while shifting and Idling surges in the mean time.
Other old a/t cars never had this idling surging and lurching even though they slam to 2nd or 3rd gear.

any good idea? thnx in advance

Last edited by wango; 10-30-2005 at 01:56 PM.
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#2 (permalink) Old 10-30-2005, 06:47 PM
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Looks like it's time to sell it..

If it's not the fluid\filter, not the TCU chip, not the TCU unit itself, then it's gota to be mechanical wear\failure. I've read that the automatic transmissions are prone to failure around 120K.

I bought my car used at about 70K, and when I had my car on a lift at about 95K, I noticed the bellhousing bolts were FRESH, brass colored anodized bolts, telling me the transmission has been dropped before. No telling what's been done to it, and it's beginning to act up again at about 117K. (low fluid symptom where when I brake really hard, and tell it to change gears, it dosn't engage for a few seconds since the rear sump looses fluid. - Engine revs beacuse there's no load, and then it engages, slamming into gear, and effectively doing the same thing as "dropping the clutch"

Last edited by bitcore; 10-30-2005 at 06:55 PM.
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#3 (permalink) Old 10-31-2005, 04:28 PM
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thnx for the advice.
Now I take it for granted that it's time to sell or swap the tranny but sad :-(
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