Engine Idling Speed
- Thread starter shiney28
- Start date
Mine does 
Its posts like the one above, that stop alot of people posting on forums. Preferring to browse and read rather than contribute.
Obviously the poster has never had a problem with a vehicle engine?
The thought behind the post was due to the fact that I had a 1999 z3 2.8 which I sold in 2004, and in its 5 year life and 23,000 miles it constantly struggled with its idling speed with countless visits to the dealer (idling too high or too low)
So, for the benefit of the previous poster. As he has identified by the responses 750 rpm appears to be the SHOCKING NEWS that healthy engines that are the same have the same idle speed. Congratulations.
Maybe now the poster might consider, not all engines are as healthy as each other on occasions.
Obviously the poster has never had a problem with a vehicle engine?
The thought behind the post was due to the fact that I had a 1999 z3 2.8 which I sold in 2004, and in its 5 year life and 23,000 miles it constantly struggled with its idling speed with countless visits to the dealer (idling too high or too low)
So, for the benefit of the previous poster. As he has identified by the responses 750 rpm appears to be the SHOCKING NEWS that healthy engines that are the same have the same idle speed. Congratulations.
Maybe now the poster might consider, not all engines are as healthy as each other on occasions.
shiney28 said:
You say you noticed the engine idle was 750rpm after 3 weeks. What was it reading in the 3 weeks prior that made you think 750rpm was wrong.
BTW, I've got a Z4MC and the idle when you start is about 1200rpm and then settles down a minute later to about 800rpm.
Alright, alright I was kidding aroundshiney28 said:
. I'll put even more smileys at the end next time to make it clear I'm only kidding.It was not related to the OP at all because there's nothing wrong in asking. I simply found it amusing that the responses all read the same. That's all, no more and nothing serious
bras0782,
No probs....took it the wrong way. I can see your amusement when you look at it now the way you intended. Apologies to you.
Hadnt taken any notice of the speed in the 1st 3 weeks, so nothing to compare it against. It was just when i did look at it and remembered the probs i had years ago with the Z3 it got me wondering what should be the norm for a Z4. (and as you say, better to ask here than ring a garage for things like this)
From cold or warm start it fires up to 750 and is constant at 750. So everything is OK.
No probs....took it the wrong way. I can see your amusement when you look at it now the way you intended. Apologies to you.
Hadnt taken any notice of the speed in the 1st 3 weeks, so nothing to compare it against. It was just when i did look at it and remembered the probs i had years ago with the Z3 it got me wondering what should be the norm for a Z4. (and as you say, better to ask here than ring a garage for things like this)
From cold or warm start it fires up to 750 and is constant at 750. So everything is OK.
I know this is an old thread but my 2.2 z4 seems to fire up at 1100 and then settle to 750 after a few mins recently, sometimes smells slightly rich too. Is this a problem?
thanx- this seems new to my car- maybe just needs a tune.
Nah this is perfectly normal Paddy - its the car running in closed loop startup mode. Basically this means that it uses a standard set of pre-determined fuelling and timing parameters (based mostly on Intake air temp i think!) on the ECU mapping to maximise warmup time and more importantly, stop the engine from stalling. Closed loop over-richens the fuel mixture which is required for a cold engine; as the fuel does not atomise as well and can condense on the cylinder walls. It is also becuase the O2 sensors in the exhaust cannot reliably detect the emissions when cold.
After a minute or so, the ECU switches to 'open loop' mode which monitors O2, timing, knock etc. The engine will then slow down to its normal idle pace with normal fuelling.
Hope that explains the rich smell
After a minute or so, the ECU switches to 'open loop' mode which monitors O2, timing, knock etc. The engine will then slow down to its normal idle pace with normal fuelling.
Hope that explains the rich smell
cheers ed- very technical!
Shipkiller
Lifer
EdButler said:Nah this is perfectly normal Paddy - its the car running in closed loop startup mode. Basically this means that it uses a standard set of pre-determined fuelling and timing parameters (based mostly on Intake air temp i think!) on the ECU mapping to maximise warmup time and more importantly, stop the engine from stalling. Closed loop over-richens the fuel mixture which is required for a cold engine; as the fuel does not atomise as well and can condense on the cylinder walls. It is also becuase the O2 sensors in the exhaust cannot reliably detect the emissions when cold.
After a minute or so, the ECU switches to 'open loop' mode which monitors O2, timing, knock etc. The engine will then slow down to its normal idle pace with normal fuelling.
Hope that explains the rich smell
You got that backward.
When the engine is first started up, it is on Open-Loop mode, which is a pre-programmed mapping internal to the ECU.
When the engine is first started, the Air-Pump starts up and injects air (oxygen) into the exhaust manifold to help burn off any unburnt fuel, reduce emissions and to help heat up the O2 sensors. It does this for 90 seconds then terminates. Also during this time, the heating elements internal to the O2 sensors (BMW uses four wire sensors), heat the sensors to approx. 600' (optimum temp for O2 measurement). When those sensors get within a set temperature range, about 500', the ECU then puts itself into Closed-Loop mode, using the pulsed-voltages from the O2 sensors to determine the Fuel Charge (based on fuel pressure and injector pulse width) and timing advance. There are other variables but those are the main ones.
Based on outside temp, and the initial temp of the O2 sensors, the car could be in open-loop for 30 seconds or four minutes. The O2 sensors heat up VERY quickly.....
I don't want to get too deep here, but that is the jist of what happens...
