Stumbles at Idle

[JMI]

The Car: 1989 535i Auto 125,000 miles

The symptoms: Happens only at idle (about 700 rpm). The engine will start to stall, rpm dropping off, and then will surge momentarily to about 1100 rpm and then settle back to 700 rpm. Sometimes it will completely stall. I can usually prevent this surge/stall by slightly stepping on the accelerator.
There appears to be no regular pattern when this happens except maybe when slowing quickly.
Stomp test gives 1444 - no code.
Can't find any vacuum leaks, but have not ruled that out altogether.
Have cleaned ICV throughly. It buzzes when engine runs. Resistance is in range -approximately 40/20/20.
Throttle Position Switch checks out OK.
Tempted to change out ICV but don't want to spend $145 bucks for nothing.
Been wondering if it could be a fuel delivery problem but wouldn't that show up at any speed?
Any ideas what to try next?

TIA

Jim

[632 Regal]

fuel pressure or vacum leak is my guess. Did you reboot the computer yet?

[JMI]

fuel pressure or vacum leak is my guess. Did you reboot the computer yet?

Did the shogun reset if that's what you mean.
Wouldn't a vacuum leak be more steady instead of this intermittent deal?

Thanks

Jim

[califblue]

if you would have used the Search feature ...you would have found this...
http://www.bimmer.info/forum/showthread.php?t=21305

[JMI]

if you would have used the Search feature ...you would have found this...
http://www.bimmer.info/forum/showthread.php?t=21305

Going to check the crank position sensor and the oxygen sensor now.

Thanks

[JMI]

Going to check the crank position sensor and the oxygen sensor now.

Checked the crank position sensor (pulse generator) and the resistance between pins 1 and 2 is 540 ohms on the dot. So that's good.

The oxygen sensor is going to be a little harder to test... have got to find it first :p

Jim

[BillionPa]

if you have never replaced it, it would be good to do so, since it affects fuel econ as well.


.... check your distributer and ignition coil.

[JMI]

if you have never replaced it, it would be good to do so, since it affects fuel econ as well.


.... check your distributer and ignition coil.

The oxygen sensor was replaced by PO about 20,000 miles ago. Replaced distributor and rotor as well as spark plugs and ICV, that still hurts. Still no go :(

About the ignition coil, as per Bentleys:
Primary Coil, terminals #1 and #15 should = 500 ohms + or - 10% / reading below 200 ohms.
Secondary Coil, terminals #1 and #4 should = 6000 ohms + or - 10% / reading 9700 ohms.

Would tend to indicate it was bad but I'm wary of throwing more expensive parts at the problem. I have a hard time understanding how if the coil is bad that it only shows itself at idle.
Could someone explain that?

Thanks

Jim

[BillionPa]

have you replaced your DME relay?

[JMI]

have you replaced your DME relay?

Replaced DME & Fuel Pump relay a while back - 5000 miles ago.

Jim

[BillionPa]

it almost sounds like the car begins to stall, then whatever mechanism thats loosing power gets power, and the car tries to "start" while its running, causing the idle to jump to where it wont stall. (no starter motor involved though)

possible loose solder point in the DME?

[JMI]

it almost sounds like the car begins to stall, then whatever mechanism thats loosing power gets power, and the car tries to "start" while its running, causing the idle to jump to where it wont stall. (no starter motor involved though)

possible loose solder point in the DME?

I have to search some threads to see if I want to go that route :p

[JMI]

Well I'm fed up and ready to buy some parts. Going to replace the crankshaft position sensor (as per 'califblue').
Also thinking of replacing some hoses.

I'm trying to identify the following part(s):

http://usera.imagecave.com/jmi/535i_id_me1.1.jpg

http://usera.imagecave.com/jmi/535i_id_me2.2.jpg

The hose ties into the activated carbon filter but I can find no reference to the electrical part.

TIA

Jim

[BillionPa]

no clue, is it an air intake temp sensor?

the hose goes from the carbon filter to the intake manifold to inject fuel.

[JMI]

The Car: 1989 535i Auto 125,000 miles

The symptoms: Happens only at idle (about 700 rpm). The engine will start to stall, rpm dropping off, and then will surge momentarily to about 1100 rpm and then settle back to 700 rpm. Sometimes it will completely stall. I can usually prevent this surge/stall by slightly stepping on the accelerator.
There appears to be no regular pattern when this happens except maybe when slowing quickly.
Stomp test gives 1444 - no code.
Can't find any vacuum leaks, but have not ruled that out altogether.
Have cleaned ICV throughly. It buzzes when engine runs. Resistance is in range -approximately 40/20/20.
Throttle Position Switch checks out OK.
Tempted to change out ICV but don't want to spend $145 bucks for nothing.



Unbelievable!
Posting, reading, playing parts jockey. Sensors, sensors, sensors!!! Checked them all or so I thought. Checked the resistance/condition of spark plug wires twice. Saw no need to replace. Not once anywhere does the pulse generator/cylinder ID sensor - #9 (http://www.realoem.com/bmw/showparts.do?model=HD23&mospid=47408&btnr=12_0049&hg=12&fg=05) come up.
Maybe because the pulse generator is generally included with spark plug wires it does not get mentioned. When someone replaces the wires in an attempt to fix an idle problem what really is doing the fix is the new pulse generator.
Bentleys only shows it in a picture where it plugs into a wiring connection but no discussion of it or how to test it. So much for the Bentley BMW bible :(
Arrrggghhhhhh
Kudos to Eastside Bavarian, Issaquah, WA (424 392-4450) (http://www.eastsidebavarian.com/) for pinpointing the problem. 1 hour charge for the diagnostic. Replaced the spark plug wires/cylinder ID sensor myself, saved a few bucks.

The car is now again a joy to drive :D

Thanks to all who offered their help!

Jim

[shogun]

http://imagizer.imageshack.us/a/img844/6393/m30intake9.jpg
As for idle control I just found this comment and pic:

There's four culprits there, the idle control signal (the larger looking hose in the center-bottom of the pic), the fuel pressure regulator signal (the tiny port on the upper left), the fuel tank vapor vent (from the center), and the plenum sump drain (on the upper right). Check the integrity of those four pieces of tubing and their connections.