Cold start issue getting worse

[benebob]

My new in Feb to me 06 955i has a cold start issue.  Starts just fine all the time but idles around 500 or less for a good 5 seconds, will sometimes stall, then it revs up to 1500 and is good to go.  If it stalls, it'll take the normal idle when you restart, if you give it any gas until it reaches 1500 it'll also stall.  9k miles, serviced well by the previous owner (a VW of NA master mechanic I'm told)   Any ideas where to look at first.  Tried a reset by starting and letting it relearn the warm up procedure and it didn't change anything.  Runs good overall, a bit of popping from the stock muffler but not nearly as much as my 885i.

[John Stenhouse]

Sounds like a sensor fault, being injected it has cold start activated by sensors for outside temp. that sounds like its not reading correctly. No help really as I don't know where that sensor is.

[benebob]

It has me stumped as it does it regardless of the outside temp and is gone in no time, or upon a restart if it stalls.

[Timbox2]

Id probably be inclined to look at the ol stepper motor/piston as again sounds similar to the issues I and some others have had. mine only got fixed after a new stepper but some have had luck by cleaning, youve gotta  be careful though if you go taking it apart, and watch what lube you use, probably best to use a plain carb/injector spray. Yes, it requires tank and airbox removal. There is a temp sensor also in the airbox, Im not aware of any other temp sensors but dont take that as gospel.

Oh and finally, if you do go this route, dont forget to check that the little sponge gasket is in place on the idle housing before you put the airbox back

[John Stenhouse]

Scratch my reply then if it does it regardless of temp, try Tims fix and while your there check the vac hoses too.

[Bixxer Bob]

I was holding off suggesting the stepper motor because it involves cash to replace, but as Tim says, you could try cleaning it first.  The temp sensor in the airbox is used by the ECU to work out how much oxygen there is in the air going into the engine.  The other temp sensor is in the thermostat housing and senses the coolant temp.  The ECU uses this value to regulate the fan and to decide what the tickover revs should be.

It does sound like a sticky stepper motor though.  I've cleaned mine and done everything else that I can think of, and still have a tickover problem.  It starts ok, revving to about 1800rpm then dropping to about 1500 and then decreasing as it warms up.  Completely normal.  But then when coming to a halt it drops to about 900 rpm and only creeps up to 1200 (where I have it set at) after a minute or two.  It's bloody annoying.  It looks like I'm going to have to replace it.  Funny thing is it cycles ok if you run the diagnostic test.  It's got me baffled at the moment.

[Chris Canning]

Since having a new map blown in before we went away mine has been all over the place,trying to separate the fuel map from the rest is my problem,now we've got got home it starts and runs like a good'un but in Spain in the hot weather it's been a bit of a tinker,but before doing anything drastic still need a few more decent nights sleep and a lot more thought :icon_wink:

One thing is for sure must be close to Metals map any speed you like and still 60 odd to the gallon.

After I have been back to shop and found out what map it is I'll do another post.

[Dutch]

60+ mpg, that's impressive. Even with the big UK gallon thats better than 21 km on a liter. Mine does about 18-19 km/l.

[benebob]

Why would the stepper or a temp sensor not work the 1st start then work the 2nd or even after a few seconds?  CI'm still not quite back to doing too much work myself yet from getting hit so I'd rather not chase  things w/o being kinda sure ifyou know what I mean.

[Chris Canning]

60+ mpg, that's impressive. Even with the big UK gallon thats better than 21 km on a liter. Mine does about 18-19 km/l.

Well that isn't normal for mine it's always been around low 40's to the gallon the way I ride it,the hike in mpg is down to the new map.

[Bixxer Bob]

Why would the stepper or a temp sensor not work the 1st start then work the 2nd or even after a few seconds?  CI'm still not quite back to doing too much work myself yet from getting hit so I'd rather not chase  things w/o being kinda sure ifyou know what I mean.

I don't think the temp sensor has anything to do with your problem but the only way to be sure is to plug in TuneECU and have a look.   

We aren't saying the stepper motor is broke, just that it is sticking hence the suggestion to clean it.  If it's sticking some of the time you get the symptoms you describe.  As for it being fine when you start up, the ECU goes through a process when you turn the ign off. It parks the stepper at a pre-determined point, saves all the trim information to memory then shuts itself down. If you listen you will hear a click a couple of seconds after turning the ign off. That is because there is a relay which is controlled by the ECU that provides its power.  This allows the ECU to control its own power supply independently of the ign.

[benebob]

Still not sure I grasp how it would only get stuck every cold start and if it does stall that it is unstuck every second time you start it.  I've just not had something not stick so methodically.

[Chris Canning]

Bixxer and Metalguru are way ahead of the game with mapping well ahead of me,but there's one thing I'm sure of it ain't an exact science,I had a new map blown in a week or so before out trip,I knew from the popping and banging it was running lean so expected good MPG,but in town in hot weather it was an absolute nightmare,come home runs like a charm!!!

[Bixxer Bob]

As I said at the beginning mine is doing something similar and I've not worked it out yet, so only tabling ideas. 

@Chris; yours will have trimmed itself back to where it needs to be.  Bear in mind it only stores trim adjustments when pre-determined criteria are met.  My guess is that the dealer put in a standard map (that's all he can do with theTriumph tool unless he used something else) and then reset the trims and then wound back the long term fuel trim to whatever the book says it should be. This is like changing the main jet in a Carb.  If it was wound back a long way it would run as you describe but using the feedback from the O2 sensor the ECU would eventually put it back where it needs to be. 

[Chris Canning]

At the moment I've half a dozen balls up in the air with the bike things that need sorting but I shouldn't complain too much thought for a while the speedo was reading slow or the traffic was,ran the bike out today 95 on the speedo shows 112 on the GPS,no wonder we did Portsmouth/B'Ham in 2 hours flat must have been running around the 115 mark  ,and finally found the 02 plug which was where you said but I forgot to take it on the trip ran quite well today with it in.