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E34 (1989 - 1995)

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  #1  
Old 05-15-2013, 08:50 AM
mattv8188 mattv8188 is offline
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Location: Plano, Tx
 
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Mein Auto: 1995 BMW 525i
E34 1995 BMW 525i Rough Idle

Hello everyone,

New user and first time post!

I have a rough idle on a 1995 BMW 525i. When I start the car, the idle is so rough that the engine cuts off. So, when I start it again, I have to immediately press on the gas for about 10 minutes until the engine warms up. Once the engine warms up, I release my foot from the accelerator and the car idles on its own. However, it still idles rough....just not as rough as before where it would kill the engine.

When I am at a complete stop at a red light....the engine idles so rough that the car starts shaking/jerking forward. It is like I am trying to hold back a big dog from chasing a cat.

What I have done so far:

The Boot:

(Looking at the boot from an ariel view on the drivers side (american side) of the car) There are two tubes that go into the bottom of the boot. I disconnected the right tube, capped the tube I disconnected and the part of the boot it went into and started the car. No rough idle! However, when I went to back it out of the driveway, I couldn't gas the car without the engine dying on me.

So I reconnected everything back to where it was and the rough idle is back...but i can at least gas the car without the engine dying. However, the engine idles very rough when I am a red light.

My back yard mechanic is not sure, but his best guess is that the mass air flow sensor might be the problem. I am not sure that is correct because I replaced that damn thing a little over a year ago...I think. I'll have to check my receipts.

Any help would be greatly appreciated.
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  #2  
Old 05-15-2013, 09:01 AM
BMR_LVR's Avatar
BMR_LVR BMR_LVR is offline
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Location: Asheboro, NC
 
Join Date: Dec 2008
Posts: 5,264
Mein Auto: 1992 525i
At work so I can't go into details right now but:

1. Get a Bentley manual. It can be searched for and downloaded here.

2. Do the stomp test. It is explained in the sticky at the top of this forum about mechanical things you need to know.

3. Check for vacuum leaks.

4. Check your idle control valve (ICV).

#2 and #4 are covered in the Bentley manual.

Good luck, and Welcome to the Fest.
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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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  #3  
Old 05-15-2013, 10:48 AM
PlasmaE34 PlasmaE34 is offline
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If the stomp test does not help, do the disconnect test of all your drivability sensors, starting with any sensor you highly suspect for this situation. These would be the afm, o2 sensor (via the relay), air temp sensor, engine coolant temp sensor, idle control valve.

Disconnecting the bad sensor will normalise your idle immediately. If disconnecting a particular sensor does not change anything, reconnect it and disconnect the next sensor. This can be done live with the car running, although certain sensors like the coolant temp sensor and icv are very difficult to get to or very close to hot metal so its better to do it all when the engine is cold.

Do not have more than one sensor disconnected at a time. Sensor locations will be found in the Bmanual.

In all cases of rough running, it is also a good practice to inspect your spark plugs and confirm that there is no oil etc in the plug's wells. Good luck.
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  #4  
Old 05-15-2013, 11:04 AM
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Bimmerfan84 Bimmerfan84 is offline
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Location: South Florida
 
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Mein Auto: 1998 528i
I believe you may have solved your own problem or at least narrowed it down. The tube you disconnected goes to the ICV I believe (which is located on the side of the block under the intake manifold).
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  #5  
Old 05-15-2013, 11:08 AM
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Bimmerfan84 Bimmerfan84 is offline
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The ICV may be stuck or the tube that goes from the ICV to the intake may have an air leak.
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  #6  
Old 05-15-2013, 11:33 AM
mattv8188 mattv8188 is offline
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Location: Plano, Tx
 
Join Date: May 2013
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Mein Auto: 1995 BMW 525i
Thanks!

1. I was one of the fools that bought the Bentley manual.

2. Did the stomp test, it came up with 1221. I tried to do it again once I found out that if I pumped the throttle five times after each code the care would give me a new code. 1221 is the oxygen sensor which I replaced two years ago. As such, I do not know how much I can trust my car's computer. I will try the stomp test again here shortly to see if there are any other codes it may give to me.

3. I also cleaned my idle control valve with carb cleaner two years ago. Back then, I had a problem with the rpms reving up and down when I put the car in park. Today, that is not the problem with the car. That is why I do not think it is the ICV.

4. As such, I think it is a vacuum leak problem. I tried spraying carb cleaner around any tubes connecting to the boot or the engine to see if it would kill the engine/rev the engine (im not quite sure what reaction I am looking for). I didn't get any reaction but maybe I'm spraying the wrong part.

Can any body tell me what the two tubes connected to the bottom of the boot do? Both the left and the right? As I said before I disconnected the right tube and the engine idoled fine. But that does not make sense to me because disconnecting without capping the tube or the tube is a HUGE vacuum leak I would think. ( I later did put caps on them put initially I did not.)

I have to fix this car before I drive it back to Texas this Sunday (from Ohio). My school starts on May 21 and I cannot miss the first day of class or second...etc. Thanks for taking the time to help me!
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  #7  
Old 05-15-2013, 11:48 AM
mattv8188 mattv8188 is offline
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Mein Auto: 1995 BMW 525i
Thanks! I'll try this. Not sure how to disconnect, however. If these sensors have a fuse in the fuse box, simply just disconnect the fuse? or if they don't... remove the sensors themselves? l think I will try and disconnect the mass air flow sensor first. Then the oxygen sensor... thanks again!
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  #8  
Old 05-15-2013, 12:02 PM
mattv8188 mattv8188 is offline
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Location: Plano, Tx
 
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Mein Auto: 1995 BMW 525i
WOW! Disconnected the mass air flow sensor and the car began idling like normal. The next question is how long can I drive the car with the air mass flow sensor disconnected? Is it a good idea? Can I drive 1200 miles home back to Texas? Or do I need to get that replaced?
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  #9  
Old 05-15-2013, 12:37 PM
mattv8188 mattv8188 is offline
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Location: Plano, Tx
 
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Mein Auto: 1995 BMW 525i
WOW! Disconnected the mass air flow sensor and the car began idling like normal. The next question is how long can I drive the car with the air mass flow sensor disconnected? Is it a good idea? Can I drive 1200 miles home back to Texas? Or do I need to get that replaced?
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  #10  
Old 05-15-2013, 01:30 PM
PlasmaE34 PlasmaE34 is offline
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You can drive perpetually with the maf disconnected.

However your fuel economy would be less than ideal. Your looking at losing up to 20%.

I suggest you get a good used oem maf shipped to you overnight. Use ebay. Should run you $50-$60 for the afm alone. Dont bother with new unless you really wanna.

Dont buy new non oem mafs.

Last edited by PlasmaE34; 05-15-2013 at 01:32 PM.
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  #11  
Old 05-15-2013, 01:35 PM
PlasmaE34 PlasmaE34 is offline
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Longshot. Clean your current afm with contact cleaner. Google for how to do this its real easy, but usually does not help.
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  #12  
Old 05-15-2013, 01:41 PM
PlasmaE34 PlasmaE34 is offline
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Quote:
Originally Posted by mattv8188 View Post
WOW! Disconnected the mass air flow sensor and the car began idling like normal. The next question is how long can I drive the car with the air mass flow sensor disconnected? Is it a good idea? Can I drive 1200 miles home back to Texas? Or do I need to get that replaced?

Thats the beauty of the drivability disconnect test. Fast efficient, accurate.

Test drive your car under ALL the conditions that you had problems with. Confirm they are gone. Then take action to buy spare parts etc.
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