Z3 1.9 takes time for idle speed to reach correct point.

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Brittas
Joined: Tue 09 Jun, 2009 12:07
Posts: 20

  Z3 roadster 1.9

Z3 1.9 takes time for idle speed to reach correct point.

Post by Brittas » Wed 13 Mar, 2019 15:08

When stopping in traffic engine stays at 1300 rpm approx. After a short while it drops to a 1000 rpm. Eventually it settles to its normal idle speed of 700-800 rpm. Is there some sort of air leakage problem here or nothing to worry about?

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colb
Joined: Sat 05 May, 2012 23:46
Posts: 651

  Z3 roadster 1.8 TU
Location: Newport South Wales UK

Re: Z3 1.9 takes time for idle speed to reach correct point.

Post by colb » Wed 13 Mar, 2019 18:17

Have a look at the butterfly in the throttle body and check its operation, it may need cleaning and a touch of lubrication to make it move correctly, it could be sticking open when the trottle is closed hence the irregular idle. Would be a good idea to whip the small idle control valve off and clean the internals with some carb spray, they do get gummed up over time, a clean would be benificial.
Also check the actual throttle cable is in good order and lubricated, smooth operation of the cable is essential, if the cable is sticking because its dry that would also be a possible cause of the slowness of returning to correct idle speed.
Colb
1999 BMW 1.8 Z3
1998 Honda Deauville NT650V

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Robert T
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Joined: Mon 12 Jun, 2006 11:35
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  Z3 roadster 1.9
Location: Cheshire

Re: Z3 1.9 takes time for idle speed to reach correct point.

Post by Robert T » Sat 23 Mar, 2019 11:26

This sounds like the behaviour of my car and what I would consider to be "normal". 1300rpm sounds a little high, but it depends upon how well warmed up the engine is - the idle speed gradually reduces as the engine warms up. The two phase reduction in rpm is what I normally see - you pull up and the rpm stays at a fast idle for a few seconds - after a few seconds it drops and if you still haven't moved after a few more seconds it reduces again. This is on an M44 engine. The only other issue is a slight cough every now and then when at the slower idle speed.

Cheers R.
Arctic Silver '99 Z3 1.9 & Black '59 Frogeye 1275cc
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Brittas
Joined: Tue 09 Jun, 2009 12:07
Posts: 20

  Z3 roadster 1.9

Re: Z3 1.9 takes time for idle speed to reach correct point.

Post by Brittas » Mon 25 Mar, 2019 08:08

Sounds exactly how mine behaves. You could have same 'problem'.

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Southernboy
Joined: Thu 07 Oct, 2010 13:39
Posts: 6423

  Z3 roadster 3.0i
Location: Johannesburg

Re: Z3 1.9 takes time for idle speed to reach correct point.

Post by Southernboy » Tue 26 Mar, 2019 08:27

Other than the above advice, you may want to check the IACV - Idle Air Control Valve. This item on the 6 cylinder models is fitted to the intake manifold below and slightly right of the DISA.
It is a very simple piece of equipment, but it has a sliding shaft in a tube type valve system. It gets dirty with black sooty stuff and tends to stick. Removal is extremely easy and cleaning can be done in minutes using carb cleaner or throttle body cleaner.
When clean, the "piston" inside should move freely when you shake the unit longitudinally. It has an electrical connector at one end which must be removed to get it off the car.
I'm assuming you have a 4 cylinder motor, so I can't say if they have a similar item as do the 6's. Perhaps someone in the know will correct me or inform you correctly. However, your car does have one.

perhaps this video link will be a help:-
ttps://www.youtube.com/watch?v=lhIM4bsjOaY

Also, here's a link to one on eBay for sale - it will provide some visuals of the item :-
https://www.ebay.com/itm/New-Idle-Air-C ... SwggpZcvI3
"Normal is overrated"
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