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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > Regional Forums > UK > UK Technical Forum > 57 E92 325d auto slows down too much?



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      01-21-2016, 01:23 PM   #1
slomotion
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57 E92 325d auto slows down too much?

Forgive the weird title, not too sure how to concisely describe this problem!

Anyway the issue is that the car seems to 'drag' as soon as I let go of the accelerator. It feels as if it's stuck in a low gear and the engine breaking is pulling it back - but the gears seem to be OK. Is this normal behaviour?

It slows down so much I've noticed I'm braking significantly shorter distances than most cars! (I think the average driver brakes too much anyway but besides the point )

I've driven plenty of other cars including: e90 320d, e46 325i and a 730d none of which exhibited this behaviour, at least not as much. All were autos.

Any ideas?
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      01-21-2016, 01:38 PM   #2
Thermobaric
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Silly question perhaps, but have you ruled out a brake issue? Like a stuck caliper?
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      01-21-2016, 01:40 PM   #3
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Doesn't sound right. Mine rolls pretty far on lift off.

Have you tried neutral?
Other than that it could suggest maybe the brakes are on slightly. Check the temps of your brakes after a drive around (try not to brake!). Be careful, they may be hot!
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      01-21-2016, 02:08 PM   #4
slomotion
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Neutral is fine, rolls forever! And tyre pressures are ok too - I run 40psi all round. So don't think it's a brake issue.
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      01-21-2016, 05:40 PM   #5
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Quote:
Originally Posted by slomotion View Post
Neutral is fine, rolls forever! And tyre pressures are ok too - I run 40psi all round. So don't think it's a brake issue.
That eliminates the brakes, so we have to look at the transmission.

Do you mean a gentle lift off of the throttle, or when you lift off fast. The first case, the car should coast without too much resistance from the drivetrain. The latter, that can be the gear change suppression function.

From BMW...

Quote:
The intention to apply the brakes can often be anticipated from the accelerator pedal being rapidly released to the zero position. If such an action is detected, the upshift is suppressed for as long as the accelerator pedal is in the zero position and the vehicle is in overrun mode.
It can feel like a form of engine braking, if you don't add throttle to get an upshift. Also remember if you are driving down hill you may not get upshifts, gears hold until you level out or apply throttle. Use of the brakes can trigger down shifts for engine braking, in fact you can deliberately instigate deliberate down shifts with brake action. The above actions can contribute to transmission drag.
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      01-22-2016, 08:25 AM   #6
Aragorn30d
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Older Autos would disengage the lockup clutch when you lifted off the throttle, leaving you with no engine braking, the engine RPM's would also drop down to idle.

Newer cars can keep the converter locked, giving you engine braking, as it saves fuel. A sign of this is that the engine RPM's WONT fall back to idle when you lift, it'll stay up.
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      01-22-2016, 03:03 PM   #7
HighlandPete
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Quote:
Originally Posted by Aragorn30d View Post
Older Autos would disengage the lockup clutch when you lifted off the throttle, leaving you with no engine braking, the engine RPM's would also drop down to idle.

Newer cars can keep the converter locked, giving you engine braking, as it saves fuel. A sign of this is that the engine RPM's WONT fall back to idle when you lift, it'll stay up.
Seems we have closed the circle with the latest autos having a coasting function, revs drop back to idle off the throttle as well. We've got the function in a VW Caravelle. Strange to see the revs drop away on the over-run at 60mph or so.

Back to the OP's situation, I'm surprised if it holds back to feel intrusive on normal deceleration. My E91 330d would stay in the same gear until about 1,100 - 1,200rpm and then change down, much as you would in a manual on easy slow downs. Current 535i with the 8-speed is even more gentle, goes down to about 1,000rpm on the gentle over-run, before a down change.

One thing I have noticed, if I'm in traffic and follow other cars slowing down without braking, (clearly they are on the over-run). I often have to use my brakes, as my car runs on much easier and I catch them up. Partly the weight of the 5-series, but it does seem to run on more than a lot of other cars. I have to nudge it down a couple of gears if I want any engine braking.

Then we know diesels and petrol engines without throttle plates (valvetronic) have little engine braking anyway, unless we use higher revs to get some additional 'friction' to assist us.
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      01-24-2016, 04:41 PM   #8
slomotion
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Thanks for all the replies guys, I will check the revs next time and also make a mental note of when it's changing gears.

Still definitely slowing down much quicker than any other car I've driven! Makes me think I'm getting less mpg as I'm giving it more gas once traffic moves off again (when driving I plan quite well so there's not a lot of braking)
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