Rough idle when Air con is on

K

Kenya

Dedicated Member
Joined
May 12, 2021
Points
28
Dear Friends,
My 1997 BMZ z3 1.9L M44 has a rough idle when an air con is on at Cold start. After 10-20 minutes, the idle become stable. Fuel trim is +-5% for both short and long. Any advice is appreciated.

Regards
Kenn
 
I'm an absolute beginner at Z3s so pardon the impertinence of trying a reply... BUT: this sounds like an issue when cold but not when warmed up. A choke / fuelling issue when cold aggravated by the extra strain of the A/C? Does it go away completely when A/C is off?
 
It may be worth cleaning out the idle control valve, as a sticky ICV would be more apparrent when the engine is cold. Check for air leaks into the intake bellows too.
 
M44 engine is known for lumpy idle, once fully up to temp what are the fuel trims showing, if they are high then look for an air leak, splits or holes in the rubber and plastic vaccum pipes and intake boot. Cleaning the idle control valve with some carb cleaner is a good idea they do get gummed up over time.
 
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