[badgerbrock72]

Hi everyone and Happy New Year!

I have noticed on recent mornings, only when the engine is cold - on my 330D Auto that when i lift off the gas, say approaching a junction, the revs drop away to idle (approx 700rpm) - this can be whilst travelling at 40mph or so.

I would have thought, with an auto box, when lifting off to allow the car to naturally slow itself (not braking) that it would have held the current gear - and if left long enough - automatically change down the ratios until eventually creeping (if left long enough) - it seems to do this once fully warmed up.

yet mine (only whilst engine warming up) drops away to idle - similar to me sticking it in neutral to let it coast.

still under warranty so should i get it to stealer, or is this normal behaviour. Ive never noticed it before and ive had the car 18 months now.

Thanks in advance

Garry

[seanblee]

Normal, for emissions reasons. Part of the engine ECU's warm-up strategy is to disable the torque converter lockup clutch, allowing some slip under load and permitting the engine to return to idle on the overrun. It's because it can keep putting fuel in at idle, whereas on overrun it cuts the fuelling completely if you're off the accelerator, which would mean the catalysts wouldn't warm as quickly.

[BanziBarn]

Originally Posted by seanblee

Normal, for emissions reasons. Part of the engine ECU's warm-up strategy is to disable the torque converter lockup clutch, allowing some slip under load and permitting the engine to return to idle on the overrun. It's because it can keep putting fuel in at idle, whereas on overrun it cuts the fuelling completely if you're off the accelerator, which would mean the catalysts wouldn't warm as quickly.

Very interesting. I've always wondered why it did this when it is cold!

[badgerbrock72]

Seanblee- thanks mate for your detailed reply, has put my mind at rest.

BanziBarn - so i take it you have same symptoms? Its strange as mine doesn't do it every day, this morning for example it behaved as it does when warm

Garry

[BanziBarn]

Originally Posted by badgerbrock72

Seanblee- thanks mate for your detailed reply, has put my mind at rest.

BanziBarn - so i take it you have same symptoms? Its strange as mine doesn't do it every day, this morning for example it behaved as it does when warm

Garry

Yep, exactly the same. I've noticed that it does it more and for longer on very cold mornings which ties in with the temp of the cats

[badgerbrock72]

excellent, thats great so i can forget it then lol!!

have a great weekend

Garry

[BanziBarn]

Originally Posted by badgerbrock72

excellent, thats great so i can forget it then lol!!

have a great weekend

Garry

You too mate.

[Reece]

Yeh i have this when cold going from 2nd to 3rd it seems like clutch slipping and it wont change up, mines a 2008 320d auto.
Thought it mite have cost me but seems this is how its supposed to be

[hey joe]

Every day a school day .....

Had a look at this yesterday. Car is 2009 built e92 330d auto. After start from cold (with OAT 7'c) idle was 750 ish rpm. Trundling thru the village (mostly downhill) in D at about 30 mph, I lifted a couple of times and sure enough the revs fell back to a little over idle with the speed nearly constant.

However, after only about a mile thru the village and onto dual carriage at normal speeds, I lifted and coasted a couple of times. The speed and revs now decayed together untill the revs flicked up as the box (presumably) changed down a gear. Like it normally does.

I wonder if this 'free-wheel-when-cold' feature described above only applies to the lower gears ??

But defo the gearbox always feels more 'slushy' when cold - mind you, I also TRY to drive it gently before it warms up !!

Happy Motoring !