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E34 (1989 - 1995)

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  #1  
Old 11-26-2012, 03:33 PM
Microtesties Microtesties is offline
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Location: Concord, NH
 
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Mein Auto: 1990 BMW 525i
Question Poor acceleration and stutter around 2000 rpm

Hey guys I've been having a problem with my '90 525i for about two weeks now. When I'm in low rpm (under 3500) my car has hardly any acceleration, if I'm cruising at 50 in 4th and mash the gas it very slowly picks up. The other (worse) problem I have is jerking/stuttering around 1800-2200 rpm at normal throttle, you can feel it below and above slightly that but it's worst in that range. I'm just about out of ideas of what it could be. The idle sounds off, kind of a wub wub instead of a hum, there are no misfires.

Here's what I've done:
-New spark plugs
-New plug wires
-New fuel and air filters
-Tested o2 sensor
-Cleaned air flow meter
-Checked for vacuum leaks
-Injector cleaner in the gas tank

My only other ideas is the distributor, fuel injector, fuel pump, or fuel pressure regulator.
Anyone else have or had this problem? Ideas on what it could be?
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Year: 1990
Model: 525i
Transmission: 5 speed
Mileage: 250k
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  #2  
Old 11-26-2012, 05:09 PM
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BMWFatherFigure BMWFatherFigure is offline
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Mein Auto: E23;E30;E38;E32;E34 +
Injector cleaner that is added to petrol is a non starter (pardon the pun) IMO. Take them out and get them rig cleaned and tested. +1 on the other things you've done. Only other constructive suggestion is to check air flow meter and TPS for smooth resistance changes over their operating ranges.
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  #3  
Old 11-26-2012, 05:22 PM
paperplane94 paperplane94 is offline
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Mein Auto: 1989 525i M20B25
How to test an AFM:
http://www.the944.com/afm.htm
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  #4  
Old 11-28-2012, 07:16 PM
Microtesties Microtesties is offline
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Location: Concord, NH
 
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Mein Auto: 1990 BMW 525i
Quote:
Originally Posted by paperplane94 View Post
How to test an AFM:
http://www.the944.com/afm.htm
Very helpful link! After messing around with my AFM I've decided that is the problem. I attempted the fix in the article it helped but needs to be replaced.
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Year: 1990
Model: 525i
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  #5  
Old 11-28-2012, 08:58 PM
robertobaggio20 robertobaggio20 is offline
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Drive with it disconnected meanwhile. The engine will perform normally after that but your consumption wont be good thats all.

Delete the codes after disconnection.
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  #6  
Old 11-29-2012, 02:29 AM
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_Ethrty-Andy_ _Ethrty-Andy_ is offline
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sure its not in limp home mode...???
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  #7  
Old 11-29-2012, 11:30 AM
Microtesties Microtesties is offline
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There is no CEL and I don't think M20 engines even have knock sensors.
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Year: 1990
Model: 525i
Transmission: 5 speed
Mileage: 250k
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  #8  
Old 11-29-2012, 04:12 PM
robertobaggio20 robertobaggio20 is offline
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Quote:
Originally Posted by Microtesties View Post
There is no CEL and I don't think M20 engines even have knock sensors.
Well your car's error reporting system is screwed or at least acting up right now. This is not uncommon for our cars.

Have you tried our suggestions ? You made no comment about that.

Another suggestion for you : disconnect the ect (engine coolant temp sensor), located just behind the thermostat area. Its blue in colour, and take a little care when disconnecting it as its in a tight spot. Do not disconnect the brown one sensor - that's informs the gauge in your dash. Then, start the engine, and go for a drive.

Check the attached tables as well.
Attached Files
File Type: pdf E34 Troubleshooting Tables Searchable.pdf (1.04 MB, 73 views)
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525i 1990, acceleration issue, idle problem, jerking, m20, stutter


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