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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 5 Series > E34 (1989 - 1995)

E34 (1989 - 1995)

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  #1  
Old 03-23-2013, 04:43 PM
jvmcdarby jvmcdarby is offline
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Location: alabama
 
Join Date: Oct 2010
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Mein Auto: 545i
rough idle

My 1995 540 great shape only 60k miles, original owner recently has a rough idle. Idle control valve, pcv valve, cam shaft sensor good. While driving and stopping at light the check engine light comes on but goes off once I speed up. Any ideas please JVMCD
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  #2  
Old 03-23-2013, 07:06 PM
E34ZombieHunter's Avatar
E34ZombieHunter E34ZombieHunter is online now
Nothin like an E34
Location: Lillington NC
 
Join Date: Feb 2013
Posts: 2,512
Mein Auto: 95 540i B/B
Have you done the stomp test?
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  #3  
Old 03-23-2013, 09:07 PM
jvmcdarby jvmcdarby is offline
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Location: alabama
 
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Mein Auto: 545i
yes I have and there is no code in obd.It is intermittent, could this be a bad coil, plug or injector ???
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  #4  
Old 03-23-2013, 09:55 PM
Mr._Graybeard Mr._Graybeard is offline
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Location: Wisconsin
 
Join Date: Oct 2011
Posts: 218
Mein Auto: '95 540i, '87 325ic
Look for vacuum leaks -- cracked intake boot (from MAF to throttle body), hoses at the throttle body or fuel pressure regulator, oil filler cap, dipstick O-rings. Those are the easy fixes. After that it's the intake manifold gaskets and fuel injector seals, which require a lot more work.

Look the intake boot over carefully first -- it's the most likely culprit. Does your idle "hunt" -- rise and fall? What does the tach read at idle?
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  #5  
Old 03-24-2013, 07:56 AM
jvmcdarby jvmcdarby is offline
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Location: alabama
 
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Mein Auto: 545i
Thank you so much for your reply. A lot of food for thought and work. I will check what you have suggested and get back. At idle the tach is about 500rpm,and no she does not seem to hunt .Thanks again. By the way I will be away from home for 2 weeks so will not work on her until I get back,JVMcD
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  #6  
Old 03-24-2013, 08:28 AM
Mr._Graybeard Mr._Graybeard is offline
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Location: Wisconsin
 
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Mein Auto: '95 540i, '87 325ic
It might be a little early, mileage-wise, to replace your oxygen sensors, but you might consider doing that too if they're original. 500 rpm is a little low -- it should be 600 plus or minus 50. That also would point to a small vacuum leak, something that might not trigger a steady error code.

You can do seat-of-the-pants testing for vacuum leaks, like spraying carb cleaner around likely weak points, but it's pretty easy to plug a vacuum gauge into the intake on this car. You can also use a MytiVac tool as a test gauge, which is what I do. A lot of big-box auto parts stores lend tools like this out ... you put down a deposit and get it back when you return the tool.

But really, a close inspection for cracks may turn up an obvious problem.
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  #7  
Old 03-24-2013, 08:34 AM
jvmcdarby jvmcdarby is offline
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Location: alabama
 
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Mr Graybeard,I thank you so much for you time and obvious knowledge . This old girl is my baby , I have owned her for 18 years and she is sweet. Now that I am retired I am slowly learning about her ,I mean slowly :o).I will take all your advice to heart ( and write it down as I am now prone to forgetting stuff:o).When I return I will go over her again and I will get back to you. Thank you again, you have been very helpful. JVMcD
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  #8  
Old 03-24-2013, 09:02 AM
Mr._Graybeard Mr._Graybeard is offline
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Location: Wisconsin
 
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Mein Auto: '95 540i, '87 325ic
Quote:
Originally Posted by jvmcdarby View Post
Mr Graybeard,I thank you so much for you time and obvious knowledge . This old girl is my baby , I have owned her for 18 years and she is sweet. Now that I am retired I am slowly learning about her ,I mean slowly :o).I will take all your advice to heart ( and write it down as I am now prone to forgetting stuff:o).When I return I will go over her again and I will get back to you. Thank you again, you have been very helpful. JVMcD
You flatter me, JV. I'm just a shadetree hack, but I've owned my 540i for eight years and have been thrashing around under the hood for a fair part of that time. Most recently I reasealed the valley pan and replaced all the intake manifold gaskets, which is a very doable job for a layman with a socket wrench set and a little time. The gaskets are well known for leaking as they age, so you may end up going there -- but it's always best to look for the easiest fixes first.

Good luck!
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  #9  
Old 03-24-2013, 12:04 PM
manuelwindows manuelwindows is offline
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Mein Auto: 1994 530i, 1977 320i
I would try just replacing the spark plugs.

I had this issue recently with a low idle and minor hesitation in the acceleration and got all kinds of stories about what it could be and different mechanics looked at all kinds of stuff and tests were done etc, and it was very frustrating, I was told I needed a new engine, that I possibly had a cracked cylinder head, and that it could be because my engine is a "Nikasil" block. All of those diagnoses by different mechanics including the dealership were incorrect.

I ended up replacing the spark plugs, the first mechanical thing I've ever really done on this vehicle and she ran like brand new after I put the new plugs in. I used Bentley's and borrowed some tools to do it. $28 for the 8 Bosch OEM plugs

Last edited by manuelwindows; 03-24-2013 at 12:06 PM.
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  #10  
Old 03-24-2013, 01:00 PM
jvmcdarby jvmcdarby is offline
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Thanks but I already have done this , glad it worked for you. JVMcD
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  #11  
Old 04-18-2013, 05:13 PM
jvmcdarby jvmcdarby is offline
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Location: alabama
 
Join Date: Oct 2010
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Mein Auto: 545i
rough idle.

A few days ago she died on the side of the road, had her trucked home and found I had a dead fuel pump. I replaced it and she is now purring like a kitten, no more rough idle . Thanks for all the replies. JVMcDarby
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