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Old 08-29-2012, 02:17 AM   #1
mcygan67
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Idling RPM irregular and hesitate to go

Hello everyone,

I am trying to determine possible causes with my E46 318i N42. It is giving the following symptoms:

I just got the oil sump gasket one of the oil separator hose replaced.

1. Occasionally (seems more frequent of late) the idling RPM (about 700rpm) is slightly irregular. Most of the time after coming to a stop at lights but sometimes just after start, whether cold or warm engine. It feels like the idling dropped and then picked up again slightly repeatedly.

2. When the above happened, the car hesitated to go when the accelerator is depressed. Once the RPM is above (i think) 1500, power is back and the drive is smooth.

3. I've also noticed that the above 2 symptoms are not likely to occur if the air-cond is switched on (which brings the idling rpm to above 900, closer to 1000).

4. On 2 separate occasions, when driving off after a cold start, the engine started knocking and significant lost of power was experienced. It felt like either the engine was misfiring or have lost at least 1 cylinder. This symptom goes away after turning the vehicle off and start again on both occasions.


Base on the above, I'm wondering if this is the start of a serious problem?

Thanks for any help.

Regards.
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Old 08-30-2012, 11:54 PM   #2
94583
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Based on your symptoms above have you checked for unmetered air leaks? aka vacuum leaks. If none found I would make sure that the idle control valve is not sticking/clogged.

Good Luck!
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Old 08-31-2012, 01:12 AM   #3
mcygan67
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Hi 94583,
I am not a mechanic and don't know how to check for unmetered air leaks. Do you know of any article/diy? Also, how can I tell if the idle control valve is not sticking?

Thanks very much.
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Old 08-31-2012, 03:04 AM   #4
mcygan67
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Additional information:

Just changed the set of spark plugs. Inspected all the old plugs and they are all fine with no sign of oil. However, I am using like 1L every 500km.

I've recently (6 weeks ago) had the sump gasket replaced as it was leaking. After that, I have not noticed any leak as the bottom of the car is clean. No sign of oil.

Any idea?
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Old 08-31-2012, 03:07 AM   #5
mkodama
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Vacuum leak.
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Old 08-31-2012, 12:32 PM   #6
Viktimize
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If you already had to replace one of your CCV hoses, good chance the others are on the verge or have a crack that is big enough to create a vacuum leak. Assuming you're over 60-100kmi, I would replace all the CCV and hoses, air intake tubes, clean ICV, etc. All that basic maintenance stuff that should be done anyway. Good chance your problem will be solved after that.
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Old 08-31-2012, 08:34 PM   #7
mcygan67
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Quote:
Originally Posted by mkodama View Post
Vacuum leak.
Thanks for the links. I have a copy of TIS but it is not very descriptive and because I am not a mechanic, I find it hard to understand. That is why I am looking for DIYs from other owners.

Quote:
Originally Posted by Viktimize View Post
If you already had to replace one of your CCV hoses, good chance the others are on the verge or have a crack that is big enough to create a vacuum leak. Assuming you're over 60-100kmi, I would replace all the CCV and hoses, air intake tubes, clean ICV, etc. All that basic maintenance stuff that should be done anyway. Good chance your problem will be solved after that.
Thanks for the information. I will attempt to locate DIYs that show me how all these can be done.

Will post back the result but this may take awhile.
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Old 09-05-2012, 07:50 PM   #8
mcygan67
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Update:
- Cleaned the MAF but did not notice any improvement.
- More research from the Net tells me that my 318i E46 N42 engine does not have ICV.
- Can't find any DIY on replacing the CCV/PCV/Oil Seperator for my car although there are plenty for other engine types.
- I have a copy of TIS but can't find any information about replacing CCV/PCV/Oil Seperator. The oil seperator is mentioned at various places like checking crank case pressure and the intake manifold.

Anyone knows of any DIY for the 4 cylinder N42? Please help. Thanks.
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Old 08-31-2015, 07:13 AM   #9
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I hope it helps
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Old 02-09-2017, 10:33 PM   #10
lhuy2733
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Hi,

Old thread revive sorry.

If you are still around how did you go with this?

Easiest and cheapest fix would be to check the hoses?

I am suffering the same symptoms.
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