Idle control

[Danny172]

Hi all
Have a 1998 z3 1.9 16v and have a problem with a lumpy idle.
The car runs and pulls great until I come the a stop, the revs go to 1000rpm and then settle down to 800 or so.
It’s when it’s idle if at 800 it’s very lumpy and you can feel it in the car rocking the car.
Doesn’t feel like a misfire, and there is no engine light on.
I had a quick feel of the intake hose from the air filter, and could not see any splits etc, but it was a very quick look as it was raining hard!
The car doesn’t seem to be running rich to me, nor do the revs hunt, nor can I hear the clacking associated with a duff disa valve.
I’ve yet to check the plugs etc, as I’ve only just taken ownership.
Any pointers in the right direction would be greatly appreciated
cheers
Danny

 

[NZ00Z3]

The M44B19 engine does have a lumpy idle. Yet, yours may be worse than normal. Maybe compare your idle with another local Z3 owner's car.

Check:

• Plugs. Old worn plugs with large gaps may contribute.
• With a scanner, check your fuel trims. If the short or long term fuel trim at hot idle is > 4%, then you may have a vacuum leak between the MAF to the engine to find.

There is also a timing adjustment that can be done to smooth the engine a little. This is a technical fix, which I'll let you know about and keep it in reserve if you are still having issues after fixing/checking the basic's.

 

[t-tony]

Get a can of Carburetor cleaner and spray around the inlet rubber while it's idling and listen for increases in engine revs and smoother running. This should detect and vacuum leaks on the inlet side.

Tony.

 

[Danny172]

The M44B19 engine does have a lumpy idle. Yet, yours may be worse than normal. Maybe compare your idle with another local Z3 owner's car.

Check:

• Plugs. Old worn plugs with large gaps may contribute.
• With a scanner, check your fuel trims. If the short or long term fuel trim at hot idle is > 4%, then you may have a vacuum leak between the MAF to the engine to find.

There is also a timing adjustment that can be done to smooth the engine a little. This is a technical fix, which I'll let you know about and keep it in reserve if you are still having issues after fixing/checking the basic's.

Thank you so much for the reply! I thought I’d start with the plugs as I have no idea when they were last changed

 

[Danny172]

Get a can of Carburetor cleaner and spray around the inlet rubber while it's idling and listen for increases in engine revs and smoother running. This should detect and vacuum leaks on the inlet side.

Tony.

Thanks tony, will give it a try

 

[Atlanta]

I have owned two z3s over the years and both have done this ,no amount of fiddling has cured the problem . The rev counter is rock solid idling at 800rpm but still get a slight judder at idle . Car drives A1 in all other respects so I live with it.