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E34 (1989 - 1995)

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  #1  
Old 10-28-2013, 06:32 PM
doomplug doomplug is offline
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Location: New Jersey
 
Join Date: Oct 2013
Posts: 10
Mein Auto: 1994 BMW 530i
Help diagnosing my car's automatic accelleration.

I'm trying my best not to sound like a total newb to the forum with a "fix my car plz" post but something is sort of baffling me. I'm asking to see if anyone else has heard of such a problem and further, I will report with my own actions as well.

I have a 1994 530i with standard trans and it seems to rev/accelerate on its own.

First I thought it was a bit of a vacuum leak, and I have yet to fix that. I'm planning on replacing the intake gaskets and cleaning out IAC/MAF.

As for a leak, in my head I felt the idle should be rough.. which it is. It seems to idle around 500 and will bounce back and forth between possibly even 300-1000 for the first 5 minutes or so in colder weather but does seem to stabilize when it reaches temperature. (assuming the gaskets are expanding to fill any gaps)

What is baffling is that its commonly building revs and not releasing them until I hit the brake/clutch. BMW's are new to me to work on. I'm wondering if there is anything else I should be checking? Is there some valve I'm not thinking of that may exist on these cars that release pressure at a certain point that is malfunctioning? would a malfunctioning o2 sensor send bad info to MAF and cause acceleration?

I'll be digging in a service manual in the meantime but I would love to hear some personal experiences from anyone on the forum.
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  #2  
Old 10-28-2013, 08:26 PM
BMR_LVR's Avatar
BMR_LVR BMR_LVR is offline
Humble E34 lover
Location: Asheboro, NC
 
Join Date: Dec 2008
Posts: 5,264
Mein Auto: 1992 525i
Just a stab here, but you may want to check/clean/replace as necessary the idle control valve (ICV).
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It's Deja Poo - as in, I've heard this **** before.
Steve

Calypso Red 1992 525i with 200K miles

1991 735i - Sold
1992 525i - Sold
1995 325is - Sold
2000 528i - Sold

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  #3  
Old 10-28-2013, 09:34 PM
_Ethrty-Andy_'s Avatar
_Ethrty-Andy_ _Ethrty-Andy_ is offline
E34 Converted E30 Fanatic
Location: Humble New Zealand
 
Join Date: Nov 2008
Posts: 6,138
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Mein Auto: E34 Touring AC Schnitzer
i agree. A dodgy ICV can cause either and both of the problems you are describing.
They are not cheap, and worth giving it a clean out and try to solve the problem that way. Also free to do this (well, you will need to get some cleaner if you dont have already). If it solves the problem great, either leave it till it plays up again, or go ahead and replace with a new part.

But it could also be vacuum leaks as well as you say, though that doesnt usually cause hunting.

You can also try resetting the adaptions in the ECU, just disconnect the ECU for 10 minutes or so and connect it again. Make sure you have the code for the Radio if its the original BMW one. If you dont have the code, then you can also reset the ECU by just unplugging it, it is found in the box by the strut tower on the right hand side of the car (passengers side of the car if you are from the USA and drive a LHD car)
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  #4  
Old 10-29-2013, 07:45 PM
doomplug doomplug is offline
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Location: New Jersey
 
Join Date: Oct 2013
Posts: 10
Mein Auto: 1994 BMW 530i
Now I feel quite stupid but wanted to give an update.. I went to work and picked up some seafoam and throttlebody cleaner, also thinking that maybe some carbon or other gunk may be holding the throttle open.. i thought i could spray out the icv and the throttlebody and see what happens, the seafoam just as a high mileage treatment and cleanout...

i sprayed out the icv/throttlebody and decided to go into the car and for whatever reason went to press on the pedal with my hand and saw that the aftermarket floor mat was up pressing on the pedal the whole time. my heel must have been putting pressure on the mat and pushing the throttle in when i let off.. i didnt expect it but the hinged throttle pedal doesnt allow that mat to go under..

i guess lesson learned, before i posted i searched the forum and all i got was this story of a family being killed because of faulty floor mats in a lexus.. i just bought the car and never thought to check, i dont even know how the previous owner could drive like that..

anyway guys, thanks for replying.. keep an eye out in the future when i put up the post of my getting the car.. once i figured it out i gave it a good ride and its amazing.
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  #5  
Old 10-29-2013, 09:08 PM
_Ethrty-Andy_'s Avatar
_Ethrty-Andy_ _Ethrty-Andy_ is offline
E34 Converted E30 Fanatic
Location: Humble New Zealand
 
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Posts: 6,138
Send a message via MSN to _Ethrty-Andy_
Mein Auto: E34 Touring AC Schnitzer
ahahaha

floormats

ill have to remember that one
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  #6  
Old 10-30-2013, 04:26 AM
BMR_LVR's Avatar
BMR_LVR BMR_LVR is offline
Humble E34 lover
Location: Asheboro, NC
 
Join Date: Dec 2008
Posts: 5,264
Mein Auto: 1992 525i
Thanks for following up. It makes sense. It also fell into the KISS category as most things usually do. Glad it was so simple for you
__________________
Most problems are usually something simple !

Quote:
Originally Posted by noego View Post
It's Deja Poo - as in, I've heard this **** before.
Steve

Calypso Red 1992 525i with 200K miles

1991 735i - Sold
1992 525i - Sold
1995 325is - Sold
2000 528i - Sold

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  #7  
Old 10-30-2013, 12:18 PM
E34ZombieHunter's Avatar
E34ZombieHunter E34ZombieHunter is offline
Nothin like an E34
Location: Lillington NC
 
Join Date: Feb 2013
Posts: 2,289
Mein Auto: 95 540i B/B
Sounds like my call with Apple support the other night. Updated my software and i had a black screen. Could hear the start up sound and everything. Turns out i accidentally turn my brightness all the way down. Figured it out before the guy even gave me some thing to try(saw some of the dim screen in the light outside).
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