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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 3 Series / 4 Series > E30 (1982 - 1993)

E30 (1982 - 1993)
God's Chariot. The E30 was produced primarily from 1982 through 1991. The cabriolet was the one exception which was produced through 1993.

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  #1  
Old 06-21-2013, 03:12 PM
vnamvet vnamvet is offline
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Location: Florida
 
Join Date: Mar 2009
Posts: 14
Mein Auto: 1987 325i
Engine Surging

Anybody have any ideas about what might be causing an engine surge of about 500 rpms ( 1,000 to 1,500) upon deceleration? Surges about 3-4 times before it settles down to a slowing decending idle upon braking or slowing. Also seems like the engine rpm doesn't want to drop down like it should when you take your foot off the accelerator. It's an intermittent issue but if it starts to surge to a higher rpm or more frequently it could be a problem. Recently replaced O2, fuel filter, cleaned all ICV/MAF, etc., new air filter,new rubber boot, replaced vacuum hoses, plugs, wires, distributor button/cap. Did a quick superficial throttle linkage lubrication. Over all runs smooth and idle is steady and dead on at 700 rpm.....
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  #2  
Old 06-22-2013, 03:51 PM
markseven markseven is offline
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Location: John 3:17
 
Join Date: Apr 2004
Posts: 7,349
Mein Auto: BMW M Power
Are you running an aftermarket chip?
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  #3  
Old 06-23-2013, 04:28 AM
vnamvet vnamvet is offline
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Location: Florida
 
Join Date: Mar 2009
Posts: 14
Mein Auto: 1987 325i
The fella I bought it from said there was a performance chip installed by the original owner and to run 91 octane....don't have a clue as to what brand/type. Yesterday, when the engine was cold, I was going down a hill near my house and when I took my foot off the accelerator, it started the surging (7-8 times) and quit when I pressed the brake pedal (that makes me think some type of vacuum association). The rpms didn't really fall back to idle as quickly as I think it should have....almost acts like a stuck throttle or dragging accelerator cable issue (or maybe a flat spot in the TPS). Today I'm going to attach a very small bungee cord or thick rubber band to the throttle mechanism to make sure it will return to the idle stop and lubricate the cables, etc. and see what happens....
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Old 06-23-2013, 05:33 AM
7pilot 7pilot is offline
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Location: i dunno
 
Join Date: Feb 2011
Posts: 251
Mein Auto: 90 Ford Tempo
1, look for unmetered air leaks.
2, Test the resistance values of the ICV. Cleaning the ICV does not repair a unit that has failed electrically.

m
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  #5  
Old 06-23-2013, 09:49 AM
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BigBoy740il BigBoy740il is offline
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Location: Arizona
 
Join Date: Jan 2012
Posts: 234
Mein Auto: 1989/1991 E30; 2000 E38
Re: Engine Surging

In addition to checking for vacuum leaks and cleaning/checking the resistance of the ICV (should read 40 ohms from two outer terminals, and approximately 20 ohms between the outer terminals and the center pin), you should check the adjustment of the throttle position sensor(TPS). It's a small, three pin black box located below the throttle body. There's two checks. First, you should have continuity with the throttle closed and hear a small click when you open the throttle butterfly. Secondly, at full throttle you should hear another click and have continuity between the center pin and outer pin.
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