Got the dreaded Misfire/Judder!

[Davies31]

So,

My 325iS manual has developed the dreaded misfire/stutter/judder. Gutted!

It seems to only happen when the throttle is being partially opened as in cruising in traffic. Seems to happen most often between 2000rpm and 3000rpm and all gears although rarely on 5th.

Usually the judder can be avoided by changing gear to alter the revs. But occasionally if you do not change up/down the judder gets worse and then there seems to be a loss of power. The engine is still running normally soundwise and revs but there is no power?

Engine smells rich when idling and seems to run hot. Fuel consumption is pretty high also. The little black cover on the airflow meter is'nt sealed very well. (If that is the air flow meter? Above the air filter with the little copper arm on a concentric spring traveling in a semi circle )

Any ideas would be very gratefully received.

Having read a couple of threads that sounded similar to my issue I guess I had better get prices and availability of: 1 Blue temp sensor. 1 Crankcase Position sensor. 1 Throttle position sensor. 1 Air flow meter.

Cheers

[Speedtouch]

Use a multimeter to test the AFM resistance, which should vary linearly as you open the flap. You may need to reposition the wiper on the resistance track if it's worn.

http://e28-535i.com/technical/AFM%20Repair.pdf

[Davies31]

Thanks for that. Where do I put the contacts to test the AFM resistance? And does repositioning the wiper mean just bending it somehow?

[redcar]

This may be of some help to test the AFM:

When i tested my AFM, it was suggested that one puts 9V across the potentiometer track, then measures voltage changes in the arm and the start of the track.

[Speedtouch]

http://www.autolib.diakom.ru/CAR/BMW/19 ... /fig02.pdf

According to this diagram, 2 is the wiper, and 3 & 4 are the track, so put a multimeter lead on 2 and the other on 3 or 4 and move the flap.

There should be a smooth progression in the resistance reading. Any dropouts (infinite resistance readings) indicate no contact being made between wiper and track.

In this case, you may need to bend the wiper arm slightly to make sure it's wiping a clean area of the track, but try spraying electrical contact cleaner or isopropyl achohol (tape head cleaner) on it first to remove any residue or oxidation.

Once you have it working consistently, seal the lid back on with silicone sealant to prevent moisture ingress.

[Davies31]

Had a better look in the daylight today. Should there be two shiney black lines on the matt black track where the wiper runs? Would this indicate a worn track?

Incidentally drove the car today and it didn't seem to happen on the way home, but did on the way out? Could it be the TPS? It seems to be intermittent.

Any ideas, anyone?

[Speedtouch]

Yes, it would indicate some wear, but this is inevitable, and may well be harmless. It wouldn't hurt to clean it as mentioned above.

Check engine earth strap and all electrical connectors (C101 on bulkhead, and the one under the inlet manifold, etc.)