E39 rough idle

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11-02-14, 17:56
satumashirt611

E39 rough idle

Yesterday noticed the idle was down to around 600 and then would settle to normal,today while ticking over for a while it almost cut out and sounded rough,drives fine when moving.noticed the other day too kinda water gulping sound when heater switched on,,wondering if they are connected in some way,heater works fine and all else is normal.new plugs are going in tomorrow.i changed the rocker gasket nearly 2 weeks ago and all went fine there.any ideas..no leaks under car..car is a 2 litre petrol e39
11-02-14, 18:01
Dod

RE: E39 rough idle

Sounds like a vacume leak is causing the idlr issue, try the rubber hoses in and around the throttle body. Try reving the car slightly to hear any loud air or sucking sounds.
11-02-14, 18:19
satumashirt611

RE: E39 rough idle

Quote:

Originally Posted by Dod

Sounds like a vacume leak is causing the idlr issue, try the rubber hoses in and around the throttle body. Try reving the car slightly to hear any loud air or sucking sounds.

tried that earlier but nothing,wondering if it could be dirty petrol.should have time to check more tomorow
11-02-14, 20:03
Gar

RE: E39 rough idle

Clean the idle control valve , remove both rubber boots from the car and check them thoroughly its very hard to see the hairline cracks in them until you have both in your hands id bet theres a split in one of them
11-02-14, 21:21
satumashirt611

RE: E39 rough idle

had a quick lookover now in the dark!!wiggled every hose and nothing.took it to the shop for a spin and idle worse and down a lot on power.getting worried now.hopefully weather will improve tomorrow so I can have a good look over...if its something expensive it will be a excuse for bigger engine...hopefully not too bad.
had a check on the coolant and it looks a bit dark but that's with torch on my phone,no oil on it or any creamy bits...
12-02-14, 10:01
Gar

RE: E39 rough idle

Unplug the maf and try driving it , how old are your plugs ?
12-02-14, 10:44
Dod

RE: E39 rough idle

I'd still bet its the vacume hoses betweeh the Air flow meter and the throttle body.
12-02-14, 13:05
satumashirt611

RE: E39 rough idle

had a few minutes so changed the plugs and no difference.barely any power now and cuts out.next to check as dod said is the hoses for cracks or wear and disconnect the maf to see any difference..
very worried about things..would a diagnostic unit show up whats up even if it was cracked hose.might know someone who can check but he may be away.
12-02-14, 13:15
satumashirt611

RE: E39 rough idle

Quote:

Originally Posted by Dod

I'd still bet its the vacume hoses betweeh the Air flow meter and the throttle body.

well just disconnected airflow meter and car runs perfect..why is it running good with this unplugged.no cutting out at all but when I plug it back in straight away cuts out....
12-02-14, 13:16
Venom

RE: E39 rough idle

Quote:

Originally Posted by satumashirt611

had a few minutes so changed the plugs and no difference.barely any power now and cuts out.next to check as dod said is the hoses for cracks or wear and disconnect the maf to see any difference..
very worried about things..would a diagnostic unit show up whats up even if it was cracked hose.might know someone who can check but he may be away.

You need something you can spray on the hoses so you can spot air being released.
12-02-14, 13:18
satumashirt611

RE: E39 rough idle

Quote:

Originally Posted by Venom

Quote:

Originally Posted by satumashirt611

had a few minutes so changed the plugs and no difference.barely any power now and cuts out.next to check as dod said is the hoses for cracks or wear and disconnect the maf to see any difference..
very worried about things..would a diagnostic unit show up whats up even if it was cracked hose.might know someone who can check but he may be away.

You need something you can spray on the hoses so you can spot air being released.

not easy with the gale force winds and heavy rain today....
12-02-14, 13:28
GERMANIKS

RE: E39 rough idle

Quote:

Originally Posted by satumashirt611

Quote:

Originally Posted by Dod

I'd still bet its the vacume hoses betweeh the Air flow meter and the throttle body.

well just disconnected airflow meter and car runs perfect..why is it running good with this unplugged.no cutting out at all but when I plug it back in straight away cuts out....

Thats it that's you sorted. Just get a new one.
Runs fine for now as it is no longer sending crazy info to the engine management. But you still need to get it sorted asap.

I think the maf-shop.com is a good bit cheaper but some managed to replace the sensor only from VAG dealer as it is the same one, as bmw does not sell the sensor on its own.