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7 Series - E38 (1995 - 2001)

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  #1  
Old 05-15-2013, 12:48 PM
signalzero signalzero is offline
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Location: Florida
 
Join Date: May 2013
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Mein Auto: 1999 BMW 740il
1999 740IL loosing rpms at speed

My car while driving at steady speeds will drop a couple 100 rpm's every 30-40 seconds and then jump right back to normal! Accelerates perfectly with no misses and the power seems great! It is just when I drive a steady speed that it does this?

I changed the plugs already!

Any ideas?
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  #2  
Old 05-15-2013, 08:46 PM
Mayorchuck Mayorchuck is online now
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Location: Farley, MO
 
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Mein Auto: '96 740iL
Put it in Sport mode and see if it stops. If it does:

http://www.meeknet.co.uk/E38/BMW_E38...dy_Misfire.htm

This happened to me. Started as you described and then started noticing the growl or 'droning' at low speeds while accelerating slightly.
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  #3  
Old 05-16-2013, 08:08 AM
signalzero signalzero is offline
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Location: Florida
 
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Mein Auto: 1999 BMW 740il
sport mode

I initially tried that and got the same problem! The only way it doesn't happen is in Manual mode, which causes me to shift gears from 2 to 4. It appears that this reduces my gas mileage and I'm not sure if by shifting into D mode while in M mode actually shifts up to a higher gear or into auto?

It seems like a computer problem that wants to try to shift when its not needed!

Will driving in M mode and shifting all the time hurt my tranny or car?

I have only had the car 3 weeks and got it for a steal at $3000. The interior and exterior are mint with an ODO reading of 89K, but found out the ODO was replaced and actual mileage is more like 160K but unsure. It came with no service records or documentation.

I also hear creaking in front end while slow turning, which I assume it needs new struts or ball joints. The A/C works great but the illumination to show the A/C on works 50% of the time! Weird

This is my 14th BMW, but my first 7 series

1996 328i
1997 328CIC
1997 328i
1999 328i
2002 325i
2003 330xi
2004 330i
2005 M3
2006 325i
2006 330i
2007 335i
2008 328i
2008 X3
2011 328i

all were manuals except the X3

got hurt and retired so now
1999 740IL

notice I'm a huge 3 series fan!
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  #4  
Old 05-16-2013, 08:12 AM
signalzero signalzero is offline
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Location: Florida
 
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Mein Auto: 1999 BMW 740il
I know from reading and word of mouth that the E38's can be tricky at times! But I have always loved them and perfect for me now at 6'4" with a blown hip and back !!
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  #5  
Old 05-16-2013, 08:43 AM
signalzero signalzero is offline
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Location: Florida
 
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Mein Auto: 1999 BMW 740il
Possibly a speed sensor?
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  #6  
Old 05-16-2013, 03:08 PM
Mayorchuck Mayorchuck is online now
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Mein Auto: '96 740iL
Sport and Manual are actually the same in my car, '96. Having it in manual prevents the torque convertor from locking up, eliminating the rpm drop. Not saying this is your issue but I think it's going to be what you find it is. Some have eliminated the issue with a trans fluid/filter change. Others, such as myself, used a friction modifier Shudder Fix. And a few who simply leave it in M all the time. Won't hurt the car IMO, but will indeed hurt the mpg's as it will no go into overdrive. Do you have any warning lights on the dash? Have you had the codes (if any)read/cleared and read again?

Speed sensor should not cause this issue. It would cause one or more lights on the dash to appear. Depending on which sensor goes bad it can affect things like speedo. Here is a great write up on them:

http://www.bimmerfest.com/forums/showpost.php?p=4205801

Do you have a Tamper Dot next to your mileage? Mileage is store in the IKE and the LCM and if they differ, it will leave a tamper dot. While most features of the IKE/cluster will work, it's very difficult to get the mileage to match.

My HVAC control module works when it wants as well. Lights, blinking lights and no lights, depending on it's mood I guess.
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  #7  
Old 05-17-2013, 10:13 AM
signalzero signalzero is offline
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Location: Florida
 
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Mein Auto: 1999 BMW 740il
tamper dot

I have a red dot next to my reset mileage, but not actual mileage! Is that what you mean?

I was told that the ODO was replaced because of pixel loss!

I assume the tranny flush and filter can't be too expensive?

But the torque converter fix? Is that something I can do in my garage or is that a pro job? What was the other fix you used?

Thanks sincerely for the help
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  #8  
Old 05-17-2013, 10:15 AM
signalzero signalzero is offline
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Location: Florida
 
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Mein Auto: 1999 BMW 740il
no lights on dash! What is friction modifier Shudder Fix
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  #9  
Old 05-19-2013, 04:02 PM
Mayorchuck Mayorchuck is online now
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Mein Auto: '96 740iL
That red dot is the tamper dot. Do you know if the PO has the original cluster?

I did a tranny fluid/filter CHANGE. Indy refused to do a flush as he says it can cause issues on high mileage cars. There are differing opinions on this.

Dr. Tranny's Shudder Fix is an additive that goes in with your transmission fluid.

I have no experience with torque convertors and hope I never do!!
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  #10  
Old 05-19-2013, 05:45 PM
signalzero signalzero is offline
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Location: Florida
 
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Mein Auto: 1999 BMW 740il
I put sea foam transmission tune up in when i bought it

Should I add that shudder fix to it also?
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  #11  
Old 05-19-2013, 05:57 PM
Mayorchuck Mayorchuck is online now
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Mein Auto: '96 740iL
That's a personal decision. It's only 4 oz. I believe. Some have resolved the issue with the a fluid/filter change. Others had to add the Shudder Fix after the change because they still had the issue. IMO, it can not hurt anything but can certainly help. So personally, I would recommend to do. Your car will have the 5HP-24. A good thread on our transmissions:

http://forums.bimmerforums.com/forum...on-Info-Thread
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