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Old 01-12-2013, 09:38 PM   #1
Rajvosa
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Idle drop (shudder) upon stopping

Hi guys,
Bought a 330ci m sport (2004) for the wife. It's an auto and a beautiful car to drive. Would have preferred a manual but she can't drive it.
Noticed two things I'd like to check to see if it's an auto thing:
1) when taking off normaly car seems sluggish for the first couple of seconds but then it wakes up. I'm taking just normal take off from lights, not spirited at all.

2) upon stopping the car at lights or whatever, there seems to be a slight engine shake/ idle drop for a second or so then normal. Like the revs drop a touch under desired range and then back up. It isn't extreme but noticeable to me. Haven't felt that before in my manual 325ci.

Many thanks
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Old 01-12-2013, 09:41 PM   #2
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Sounds like coil packs or need new injectors to me..
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Old 01-12-2013, 09:54 PM   #3
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First off I assume you have no check engine light, as you're not reporting one.

How many miles/Km?

Sounds like a couple of possibilities:

1.Vacuum Leak
Intake boots could have cracks, or not seated properly etc.

2. Fuel pump could be soft failing, and, or relay and filter

3. When you mention sluggish take- offs, I think of cam position sensors, but they would throw a light, and a code. I have experienced sluggish, downright unsafe acceleration, as a result of a failed intake cps (cam sensor)

It could be many things, if you can find someone, perhaps a local fanatic that will scan your OBC for codes, it will help immensely.

Search user jofj and see his SIG for info on your issue.

Good Luck.


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Old 01-12-2013, 10:03 PM   #4
Rajvosa
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Originally Posted by ///MPR77 View Post
First off I assume you have no check engine light, as you're not reporting one.

How many miles/Km?

Sounds like a couple of possibilities:

1.Vacuum Leak
Intake boots could have cracks, or not seated properly etc.

2. Fuel pump could be soft failing, and, or relay and filter

3. When you mention sluggish take- offs, I think of cam position sensors, but they would throw a light, and a code. I have experienced sluggish, downright unsafe acceleration, as a result of a failed intake cps (cam sensor)

It could be many things, if you can find someone, perhaps a local fanatic that will scan your OBC for codes, it will help immensely.

Search user jofj and see his SIG for info on your issue.

Good Luck.


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96kms.
It definitely isn't unsafe acceleration. Car goes but I got a feeling it's designed like this maybe on purpose to provide a gentle/soft take off if you know what I mean. (if I plant it, it bloody goes hard!)

Also rev drop is very slight...Half a second maybe...maybe I should get my mechanic to lift the revs up a touch and see if that fixes it
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Old 01-13-2013, 01:15 AM   #5
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I don't know about the 6cyl engines but with the 4cyl ones I've found that a rev drop when stopping is usually associated with a vac leak.
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Old 01-13-2013, 05:48 AM   #6
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Had both those problems. I solved my hesitation with the correct spark plugs but consider vacuum leaks, the DISA or VANOS. I've had coil packs done too but only because one completely failed.

I solved my vibration by having the idle raised, nice and easy permanent band aid fix was only by 100rpm and it solved it. I suspect VACUUM leaks but will have that solved in two weeks.

If you need anything I've got a library of part numbers for the systems in the 330i/Ci.
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Old 01-13-2013, 08:44 AM   #7
ubersaloon
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Not sure about the hesitation but my manual 325i does the idle drop all the time when coming to a stop but I've given up trying to fix it.
I don't think it's an auto-specific thing and can be caused by all manner of problems, some of which have already been mentioned.

If you can be arsed, try disconnecting the MAF sensor and see if it goes away like it does with mine.
NB doing this will throw a code and you will lose cruise control and the ability to heel-toe, which is no biggie in an auto unless your wife likes to stall it up on the brake at the lights or is a habitual left foot braker.

My theory is that disconnecting the MAF sensor forces the DME to use a basic failsafe mode or map for airflow.
With this basic (ie rich) map, there is less tendency for the idle to hunt around trying to chase some sort of balance that might otherwise be affected by a leaky, dirty or faulty component elsewhere.
Of course I could be on drugs but I'd be interested to hear what you find if you try it.

This doesn't necessarily tell you where the fault lies either but in my case it wasn't the MAF sensor.......or the DISA, OSV, CPS, CAS, ICV, VANOS, TB, coils, plugs, boots, gaskets, battery, fuel filter etc.
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Old 01-13-2013, 05:58 PM   #8
trive2
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Originally Posted by ubersaloon View Post
Not sure about the hesitation but my manual 325i does the idle drop all the time when coming to a stop but I've given up trying to fix it.
I don't think it's an auto-specific thing and can be caused by all manner of problems, some of which have already been mentioned.

If you can be arsed, try disconnecting the MAF sensor and see if it goes away like it does with mine.
NB doing this will throw a code and you will lose cruise control and the ability to heel-toe, which is no biggie in an auto unless your wife likes to stall it up on the brake at the lights or is a habitual left foot braker.

My theory is that disconnecting the MAF sensor forces the DME to use a basic failsafe mode or map for airflow.
With this basic (ie rich) map, there is less tendency for the idle to hunt around trying to chase some sort of balance that might otherwise be affected by a leaky, dirty or faulty component elsewhere.
Of course I could be on drugs but I'd be interested to hear what you find if you try it.

This doesn't necessarily tell you where the fault lies either but in my case it wasn't the MAF sensor.......or the DISA, OSV, CPS, CAS, ICV, VANOS, TB, coils, plugs, boots, gaskets, battery, fuel filter etc.

Raise the idle man, you'll barely notice the raised idle but it completely solves the issue. It still dips as the computer struggles to keep up with the adaptations, but it won't dip far enough to shudder and you wont notice it anymore.


Also, if disconnecting the MAF solves your problem, you've most likely got vacuum leaks or possibly a faulty MAF (but unlikely).
The MAF measures the air before it enters the engine and the 02 sensor measures it as it exits the engine, both working together to perfect the mixture and timing. If either one is disconnected, the engine defaults to a certain map.


I'm curious, are you saying you've changed every single vacuum line in the intake system and you still have the problem? Could that then point to a soft failing fuel pump?
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Old 01-13-2013, 10:38 PM   #9
ubersaloon
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Thanks for that.
Pretty sure the idle was already raised when I got the DME update - not by a lot but you're right, it made a difference and now it's just a noticeable dip in revs when I come to a stop, but not really low enough for it to shudder.
It used to stall quite a lot prior to this but perhaps it's worth going a little bit higher again.
I have often wondered whether this is just a characteristic of the car/engine, and specifically with the early DBW cars.

The MAF is OK - I swapped it out with another and it made no difference.
I've also pulled the entire intake looking for leaks but didn't find any, even in all those obscure, hard to see places.
And not one code, ever, except when I have deliberately disconnected something.

I've read a bit about these soft failing fuel pumps lately but the trouble is, mine would have to have been soft-failing for about 5 years now and the car otherwise runs perfectly with none of the other fuel pump related symptoms.
I haven't done much with the fuel system though, other than replace the fuel filter so my (perhaps incorrect) assumption that fuel delivery is OK may need a rethink.

Thanks again
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Old 01-21-2013, 09:10 AM   #10
Geeds
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Running 98 RON fuel? Anything less may create these issues...

Last edited by Geeds; 01-21-2013 at 09:11 AM.
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Old 01-21-2013, 09:14 AM   #11
Rajvosa
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Running 98 RON fuel? Anything less may create these issues...
Always
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Old 01-21-2013, 05:10 PM   #12
forzamilan10
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Quote:
Originally Posted by Rajvosa View Post
1) when taking off normaly car seems sluggish for the first couple of seconds but then it wakes up. I'm taking just normal take off from lights, not spirited at all.
I thought this was common in all automatic E46s, there is almost a 'dead spot' in the accelerator pedal, then it picks up quite abruptly... or perhaps my car needs to go back to the mechanic!
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Old 01-21-2013, 07:04 PM   #13
trive2
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You're talking about different things.


Since changing the spark plugs, my hesitation around 2500rpm has gone away.

However, the awful electronic throttle has a deadspot for a centimetre or so (feels like way more) before it actually does anything, then it suddenly comes on FAST. Apparently some are better than others. Mine sucks. If you push the deadzone at idle, you'll find it does lift the idle, so it does SOMETHING, but obviously not enough to feel like anything more than deadzone on the move.

Stupid stupid BMW. I hate the throttle in this car.
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Old 01-21-2013, 08:14 PM   #14
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Stupid stupid BMW. I hate the throttle in this car.
First world problem. Ride a horse!
But I think it's really the drive by wire that causes the lag. I have no issues with my drive by cable and and leg operated clutch
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Old 01-21-2013, 08:28 PM   #15
Rajvosa
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Yes sounds like what I'm talking about, the 'dead spot'. Good to know its normal
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Old 01-22-2013, 05:57 AM   #16
trive2
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First world problem. Ride a horse!
But I think it's really the drive by wire that causes the lag. I have no issues with my drive by cable and and leg operated clutch
Yeah, I've driven all sorts. Some are better than others. You don't really notice it in a manual and the cable's completely eliminate it.
There's pretty much no way to convert without losing DSC apparently;

HOWEVER... I have a friend with a manual 328Ci that runs a half cable/half electronic set up from the early days. I'm looking into that, because his gas pedal is perfect.
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