Process of elimination regarding my idle issues today..did a bit reading last night and I have a small list..if I'm wrong please excuse my lack of mechanical expertise..

Today I will check the 02 sensors are registering ok..ive read to take off air filter housing and data should show this has an affect (lean) then to spray a tiny bit carb cleaner in intake and it should run rich? If these show in my reader then sensors are ok?

I've had the maf sensor off and it looks brand new but will measure air flow at 600/200rpm and 3000rpm and compare it to the figures I have which are 17.1/44/76 kg/hr....mines is showing 24kg/hr at 600rpm but want to check other data..

I've already popped in a new air filter and new battery fitted tomorrow..

Another thing is the throttle position sensor is saying its sitting at 3% ? Reading up in that to better understand it..ive also filled car up with v power fuel as I've been using morrisons.. Probably won't help but worth a try...

If you just watch the o2 sensors readings they should cycle between around 0.3 to 1.2 or close, the engine ecu richens the mixture until the o2 sensor says it's rich, then it leans out the mixture until the o2 says it's lean, this happens many times per second, no need for faffing with filters or spraying extra fuel in... the o2 sensors are also checked by the post cat sensors and if they don't agree, i,e one is faulty, then you get a MIL light on...

Check the STFT (Short term fuel trims) these show how far away from the ecu's map the fuelling has to be to be corrected by the o2 sensors when the system is in closed loop... they should be + or - 10%, any further out indicates issues....

Don't know how far out your tickover is but mine does vary a lot of the time, the alternator is a smart one and gives power when needed and that affects it as well as the aircon, if the engine is clean with no hiccups when cruising at a constant speed and the tickover is close to it's 700rpm then i wouldn't worry too much...

The above description is greatly simplified for easy reading......  Pete
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2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand Sold
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Sold
2002 L322 Vogue 4.4 V8 Epson Green (Fatty Offroader) Sold
-Click for Project Fatty off roader-

Magic 02 readings are bouncing about between 0.025 to 0.070 and 0 025 to 0.82..will check the fuel trims tomorrow! Im slowing learning about this car and its workings so hugely appreciate the help! Cheers Pete...bedtime reading this week will be the rave manual ...lots of knowledge to soak up...

Ok I've managed to check the short term fuel trim..there's 2 sets.of readings .
First set
Bank 1 -4.4% to -10.2%
Bank 2 - 3.2 % to -10.2%

Second set are
(b1-s1) - 3.1% to 9.4%
(b1 s2) -99.2% ? Is this the problem? Thanks

Gut feeling - your MAF is on its way out. The 4.4 BMW seems very sensitive to its air flow reading being correct if the sensor is attached. Is yours showing an engine management light?

I was getting poor starting / idle / stalling engine which in the short term I resolved by disconnecting the air flow sensor ( the engine guesses the readings by other means ) which let me drive the car for a while.

What would happen is that when resetting the trim values, I would be able to see the trims drift out beyond tolerance when I accelerated moderately. (The trims seemed to only adapt on medium to full acceleration) and then the engine light would come on.

Changing the MAF resolved the idling issue and trim issues. BUT ONLY BUY A GENUINE ONE ! I tried 2 non-genuine ones first, and neither gave readings which the ECU was happy with. Bought a gen from a dealer, plugged it in, and the car was sorted instantly after resetting all the values. V8 or else ...

I've got some good maf readings here somewhere. Hold on I will have a look.
Your o2 readings are Good 😊 No7 - 2003 V8 Vogue

Here you go. These are known good readings. All loads off
600rpm idle - 17.1 Kg/hr
2000rpm - 44Kg/hr
3000rpm - 76Kg/hr.
Exactly as your info - did we get it from the same source ?

SO your idle reading is showing high..... No7 - 2003 V8 Vogue

@ fisha no warning lights or faults stored at all buddy..if I start car cold it idles at about 1500rpm for a minute or 2 then bounces between 500/600rpm. If I give it some gas in idle the revs drop,lights dim and it nearly stalls....it seems more stable with the air con switched on then after a while it does the bouncy rev trick again

@rewmer ..i googled them somewhere Yeah idles all over the place....cars going in for a full service and pcv valve/pipes ect getting replaced...got a new battery delivered today as well so that's going in shortly then hopefully addresse the idle issue

alistairh wrote:

@ fisha no warning lights or faults stored at all buddy..if I start car cold it idles at about 1500rpm for a minute or 2 then bounces between 500/600rpm. If I give it some gas in idle the revs drop,lights dim and it nearly stalls....it seems more stable with the air con switched on then after a while it does the bouncy rev trick again

Sounds to me like an air leak into the inlet manifold somewhere, it's getting extra air in somewhere, hence the low tickover...  Pete
__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand Sold
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Sold
2002 L322 Vogue 4.4 V8 Epson Green (Fatty Offroader) Sold
-Click for Project Fatty off roader-

That doesn't sound too bad then! Matter if finding said leak..one thing I have noticed is if I quickly rev car there's a huge sucking,vaccum noise from the external air inlets (gills)..probably normal as I've never had a rangey

That's weird as they aren't anywhere near the air inlet, it's right at the front of the wing, this has my elbow on it for the snorle the original one points downwards...!!!



The air leak will be somewhere past the throttle body, probably at the rear of the inlet manifold.. :thumbsup:

Admin note: this post has had its images recovered from a money grabbing photo hosting site and reinstated  Pete
__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand Sold
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Sold
2002 L322 Vogue 4.4 V8 Epson Green (Fatty Offroader) Sold
-Click for Project Fatty off roader-

Great..weekends jobs are to solve this issue(hopefully) I presume when the revs drop and all the lights dim its to do with my bad battery? Just tested it under load and its just over 11v....new one arrived yesterday and is going in on Saturday..cheers

Daft question but do you have an air filter in the housing? That can usually attribute to a sucking vacuum sound. ______________________________
Simon
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Yeah...just changed it...good point actually! I did have the air housing out to fit the drivers side headlight..i had a nightmare refitting the pipe at the bottom to the lower housing..maybe its not meeting right? Definitely never heard the sucking noise before it...only issue is I did have the problem idle before I fitted headlight