Unstable engine RPM during warm-up after parking for several days

[Aleks Mys]

Hello, all!

I own Z4 E85 2004 with engine M54B30 and 6 speed manual transmission.

After winter parking began to observe a strange start of the engine.

1. If I start the engine after 2-3 days of parking, then at the start it throws up RPM to 1500 and then, within half a second, resets them not to warm-up RPM (900-1100 rpm), but to 700 RPM where it is very close to stalling, after which is aligned to the warm-up RPM. All this happens during the first three seconds after starting the engine and only when the engine has not been started for several days.

2. When the engine warms up in the first 5 seconds after the start, the RPM arrow floats in a small but noticeable range of 50-100 rpm. Is it good?

3. After warming up, the idle speed of the engine drops to about 700 rpm and there is a slight vibration on the body of car, but if I raise the RPM by 50, then the vibration disappears.

Could this be related to some sort of RPM controller? Maybe some adaptation is needed. I had drained battery on winter parking.

Thanks to everyone who answers!

 

[Zulu4]

I'd check that the battery is fully charged and in good condition. Also do an OBD scan of the car for fault codes.

 

[SonnyA85]

Throttle body or whatever it's called may need cleaning it's near the disa valve.

Could be the disa valve is on its way out. Or it may be your vanos needs re-built.

What oil are you using and how old is it? Could be it's a thicker than spec oil in the car that takes time to warm up and become more fluid. A 10-40 oil for instance instead of 5-30.

Could be a bad batch of petrol also or spark plugs need replacing. Fill it up with new petrol elsewhere and see if that sorts it.

Italian tune up could possibly help.

 

[dwoodford1987]

Valve cover gasket leaking.

It probably doesn’t sound like it would be the cause but a lot of people make the mistake of replacing lots of other things instead of this and they just end up living with it.