MAF disconnected causes HARD shifting (auto) - BMW Forum - BimmerWerkz.com
3-Series (E36) Chat relating to the BMW 3-Series from 1992-1999. Autodoodad Specific models include: BMW 316i, BMW 318i, BMW 318iS/ti, BMW 320, BMW 323, BMW 320, BMW 324, BMW 325, BMW 328.

 
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#1 (permalink) Old 08-22-2014, 02:08 PM
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MAF disconnected causes HARD shifting (auto)

Hello All!

I've got a '97 328i convertible.

I had a bad MAF where the car would hardly idle with the MAF connected, but would idle fairly well with it disconnected. However, if I tried to drive it with the MAF disconnected, the auto trans would shift with a real hard clunk at each gear.

I cleaned the MAF to no avail so I ordered an aftermarket MAF and installed it.

The car ran great again, shifted real smooth when I took it around the block. When I came back to it that afternoon, it was difficult starting and the "sproket" light was on on the dash (as it had been with no MAF.)

I cleaned the connector plug to the MAF, plugged it in and viola, it worked again! So I took it for a drive and about four miles into it the "sprocket" light came back on and the rough shifting returned.

Now, cleaning the connector has no affect and I wonder it it was just coincidence that it seemed to work before.

Any ideas?
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#2 (permalink) Old 08-22-2014, 03:35 PM
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These are the OBDII codes it's throwing:

P1250 -- unknown

P0170
P0173 -- upstream O2 sensors

P0740 -- torque converter clutch circuit open.

also
P1188 - fuel control, bank 1, sensor 1
P1189 - fuel control, bank 2, sensor 1

P0442 -- evap. sys. small leak detected, faulty purge solenoid, fuel vent solenoid, loose or faulty purge line or fuel cap.

The torque converter clutch solenoid worked when the MAF was first replaced, didn't work with old MAF disconnected and doesn't work at all now.
I am assuming there is a chain of symptoms springing from just one or two causes.
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#3 (permalink) Old 09-01-2014, 02:50 AM
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Question mr

Hi I have a BMW e46 318i 1999 model automatic and the air flow is disconected but the car work and has power but it shows a telle light comes on next to the D sign when driving but when we connect the air flow the light does not appear but the car does not have the power any more. Please tell me what to do and how this is bad as I use it when disconected is it put the engine to denger. Or do I need a new air flow.
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#4 (permalink) Old 09-01-2014, 02:56 AM
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Question mr Bonginkosi

Hi I have a BMW e46 318i 1999 model automatic and the air flow is disconected but the car work and has power but it shows a telle light comes on next to the D sign when driving but when we connect the air flow the light does not appear but the car does not have the power any more. Please tell me what to do and how this is bad as I use it when disconected is it put the engine to denger. Or do I need a new air flow.
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#5 (permalink) Old 09-01-2014, 05:34 PM
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Quote:
Originally Posted by George Delves View Post
These are the OBDII codes it's throwing:

P1250 -- unknown

P0170
P0173 -- upstream O2 sensors

P0740 -- torque converter clutch circuit open.

also
P1188 - fuel control, bank 1, sensor 1
P1189 - fuel control, bank 2, sensor 1

P0442 -- evap. sys. small leak detected, faulty purge solenoid, fuel vent solenoid, loose or faulty purge line or fuel cap.

The torque converter clutch solenoid worked when the MAF was first replaced, didn't work with old MAF disconnected and doesn't work at all now.
I am assuming there is a chain of symptoms springing from just one or two causes.
Check all fuses and hoses for a vacuum leak. Strictly speaking, when the MAF is replaced, adaptation values should also be cleared (as the DME will have attempted to compensate for faults by adjusting the air/fuel mixture). Your car will eventually re-learn the correct values and compensate accordingly, but clearing the adaptation values makes this process a little easier by reverting the values to factory default settings. When checking for vacuum leaks, check the intake boot as often cracks will appear underneath and are not immediately apparent.
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#6 (permalink) Old 09-02-2014, 11:04 AM
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Thank you David.

I am planning to replace all of the intake-associated vacuum hoses as they are all looking pretty sorry and this would be simpler than chasing what could be multiple vacuum leaks.
The intake boot, however, looks like it may have been replaced in the not to distant past, but I will inspect it carefully when I have if off.

Meanwhile, is there a listing somewhere of the sizes of all of these different hoses such as the CCV, ICV and Fuel Tank Breather Valve, etc.?
I would like to purchase enough of the proper sizes of hose before disassembling the intake components if possible.

Thanks again!
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#7 (permalink) Old 09-03-2014, 06:01 AM
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George, input your VIN number into RealOEM.com for exploded parts diagrams and original part numbers. I source the bulk of my parts from Pelican Parts and Schmeidmann.
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#8 (permalink) Old 09-03-2014, 08:15 AM
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Thanks David.
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