318i e46 rough idle misfire

[nickoz]

hey fellas hows it goin got a bmw 318i e46 4cyl runs like crap at idle changed plugs, o2 sensor, checked leads for ohms and primary on coil, air flow meter good. long term fuel trim met its limits rich, removed plugs 1,2 and 4 are black number 3 is clean any suggestions

[oldford]

Heavy (maybe constant) misfire on cylinder 3. This lets O2 into the exhaust. The O2 sensor is fooled and sends a signal mixture to lean. Ecu will enrich, enrich, ......

Do you have a good spark on cylinder 3?
Do you have fuel at cylinder 3?
To test the fuel: change the injector from cylinder 3 with say 4. Does the problem stay at cylinder 3? or does it go to 4? When it goes to 4 replace injector.
When it stays at 3: remove injectors to see spray pattern while starting. Is there fuel at cyl. 3?
No, check wiring.
Yes, measure compression.

[Meat-Head]

Heavy (maybe constant) misfire on cylinder 3. This lets O2 into the exhaust. The O2 sensor is fooled and sends a signal mixture to lean. Ecu will enrich, enrich, ......

Do on.

AWESOME post dude, think you should be called 'Alton Toweres', because
that's where "wounders never cease"

[ADTS]

and you cant rule out an air leak in pipes or breather. and seen air flaps in manifold colaps and damage valves.

[bebiloku]

hey fellas hows it goin got a bmw 318i e46 4cyl runs like crap at idle changed plugs, o2 sensor, checked leads for ohms and primary on coil, air flow meter good. long term fuel trim met its limits rich, removed plugs 1,2 and 4 are black number 3 is clean any suggestions
clean all spark plug after change coil no3 with no 4.