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Please help identify cause of rough idle?


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silvermist366
New User

May 14, 2012, 7:05 AM

Post #1 of 4 (1327 views)
post icon Please help identify cause of rough idle? Sign In

Year of vehicle- 2001
Make of vehicle- BMW
Model of vehicle- E46 325ci
Engine size- 2.5

Hi I'm new to this forum. I've tried quite a few web sites for help and visited nearly all the local garages around my area. The nearest BMW dealership is 133 miles away hopefully someone on here can help narrow down what could be the fault Unimpressed anyway here goes. When the engine is cold, it starts fine and the rpm goes to 1k and stays there for about 30secs or so before starting to drop to normal idle speed and that's when the problem starts. As soon as the rpms starts to drop, the car shakes and rumbles pretty violently and if I leave things as they are then the check engine light comes on but if I hold the throttle to keep the rpms above 1k and wait for the engine to warm up then let go, the rpms drop smoothly and there's no check engine light but I've noticed an increase in fuel consumption. So when the engine is cold I MUST hold the throttle above 1k to warm up or else the rpms will drop and cause engine misfire and check engine light comes on but after the engine is warmed up then everything works as normal which makes it extremely hard to identify the problem but the fuel consumption is really biting me because usually 1/4 of fuel lasts up to 109 miles but now its about 47 to 50 miles per quarter.So as suggested by the mechanics I've visited, the O2 sensors and ignition coils have been changed because when the code comes on, it says cylinder 4 misfire with fuel cut off according to the scanner. Then it was suggested that full service should be carried out ie change of all sorts of filters and oil etc so that was also done but problem didn't solve. Then it was suggested that throttle body and icv valve needs to be cleaned, so I asked that to be done too and that improved things a little. Its not as rough as before when cold and fuel consumption has improved a little but the misfire when cold and increased fuel consumption still persists. So what else could be faulty? Its starting to seem like something I have to live with and I'm pretty sure the car could fail emission tests. Any suggestions on what else could be causing this issue?



(This post was edited by silvermist366 on May 14, 2012, 7:07 AM)


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

May 14, 2012, 7:29 AM

Post #2 of 4 (1305 views)
Re: Please help identify cause of rough idle? Sign In

What is the code number being set when the check engine light comes on?



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



silvermist366
New User

May 14, 2012, 8:45 AM

Post #3 of 4 (1281 views)
Re: Please help identify cause of rough idle? Sign In

the code was P1349 but the check engine light doesn't stay on all the time. If it comes on then it will disappear once the engine has warmed up. Tricky huh.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

May 14, 2012, 9:41 AM

Post #4 of 4 (1269 views)
Re: Please help identify cause of rough idle? Sign In

That's misfire cylinder 4 with fuel cutoff. You're going to have to get to the bottom of why that cylinder is misfiring.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.





Please help identify cause of rough idle?


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