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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 Yesterday, 09:44 PM
FabianE34 FabianE34 is online now
Fabian
Location: Massachusetts
 
Join Date: Oct 2014
Posts: 8
Mein Auto: 1994 525i
Bad idle, shuts off

LOL my car is always giving me some problem as soon as i have plans to do something the next day but anyways, 1994 525i , when i start my car it idles around 400-500 rp,s and itll try to give itslef the power to stay on but itll die out. To keep it running i have to keep on pressing the gas pedal to keep up the rpm. It was misfiring so bad and i noticed a weird smell. I also did the stomp test and fault code 1215 came up which i think is MAF sensor. I took that apart and checked the intake box and the throttle body and it was all good, EXCEPT that i noticed a bit of motor oil in the throttle body. I'm not sure if it was like that when my mechanic put in a new motor for me or if theres an oil line/tube that can be leaking around the intake system. I cleaned the MAF and still did the same thing. Also cleaned out the throttle body. Honestly IM almost sure theres a vacuum leak somewhere because the brake pedal went stone hard while i was driving and would only be easy to depress if i floored the gas.
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  #2  
Old Today, 10:21 AM
ThoreauHD ThoreauHD is offline
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Location: Virginia
 
Join Date: Feb 2006
Posts: 685
Mein Auto: 02/1994 530i 8cylinder
See the brake booster vacuum leak thread below. Also keep in mind that your MAF may simply have gone bad.
But as that is one of the most expensive parts on the car, explore the vac leak first.
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  #3  
Old Today, 12:57 PM
tristero tristero is online now
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Location: 805
 
Join Date: Mar 2014
Posts: 29
Mein Auto: 95 525i
When I was troubleshooting a misfire, at one point, I did get a MAF code. I sprayed it with MAF-cleaner, cleared codes, and it didn't come back.

(I did have oil in my spark plug wells, and I also changed my Valve Cover Gasket, just in case the misfire was caused by that oil; but my coil boots were also gunked and cracked, so I also replaced those and bought new plugs; one of my plugs was burnt - so ultimately, my problem could have been caused by ANY of that; including, maybe a loose intake boot on the throttle body that I snugged down).

What I'm saying is: sometimes, the root cause of these kinds of problems can be hard to pin-down, and your best bet is to check out everything that's a potential cause, and eliminate those causes as possibilities - and when you've got everything buttoned down, (which is not easy on cars this old) - it should run right as rain.

Idle issues seem to be primarily related to the Idle Air Control Valve, or problems with intake leaks, vacuum leaks, throttle body, or MAF. I think the MAF code points at the MAF, but it could also be an intake leak.

One great test for the MAF is to unplug it (at the connector) and see how the engine runs. (mine hunted like crazy) - some MAF failures will do crazy things. Try spraying it with some MAF cleaner (not carb cleaner! - harsh solvents can damage a MAF). You can hose-off any contaminants or deposits, dust, oil, or other crud that's sitting on the MAF and interfering with how it responds to air flow. If it's not burned out, that should clean up the MAF's behavior. Another thing to try, is if you have a known-good MAF from another car (same model) - then swap them. (otherwise, swap it with a brand-new MAF; which is costly, like $200-ish).

Otherwise, you can order new intake gaskets, throttle body seals, and probably injector seals, and start taking the whole intake plumbing apart, and look for leaks, and replace the seals and gaskets which are a primary source of leaks that will cause inconsistent behavior like this.

Idle Air Control valve is sort of a bypass to the throttle body - when that throttle-plate is fully-closed, the air flows through the ICV, and that's how your idle is controlled. So if that's leaky, or clogged, or the adjustment is off, that can affect your throttle.

These articles are some good background info:
http://www.pelicanparts.com/BMW/tech...leshooting.htm
http://forums.pelicanparts.com/porsc...how-works.html
http://www.bimmerfest.com/forums/sho...d.php?t=379225

Great DIY procedure:
http://www.bimmerfest.com/forums/sho...d.php?t=759718

ANother one with pictures (dead links though)
http://www.bimmerwerkz.com/forum/3-s...ing-48667.html
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1995 525i M50TUB25 Automatic; 231k miles.
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