Fellow BMW techs...especially those with 4.6's

[imola38]

As a BMW technician working basically on my own I rarely see, much less work on another E53 4.6is. See loads of 3.0's and 4.4's though.

I have an 03 4.6is bone stock with 97k miles. I've had the truck about a year and love it so far. Though I will say that coming from an E38, I can't tell it wasn't built in Germany and isn't nearly as smooth. But, it's got a fat V8, makes great sounds and looks damn good!

Couple nagging problems that are irritating and software hasn't cured.

-When taking off, especially when cold, acceleration just isnt smooth at all. It's not a shifting concern because I 90% of the time use manual mode which eliminates the typical "bang" into first every few stops. It's more like the engine has a lean spot or something. It's really "herky jerky" and annoying. It seems to get better when warm but I still notice it. Is this just a trait of the higher comp. 4.6 variant? Any other 4.6 drivers notice this?

Also, the aforementioned transmission slam at a stop which is rediculous. My 740i always shifted creamy smooth. The only way I've found around it is to drive in manual mode and gently downshift myself and it never happens.
I've flushed the trans using factory Esso fluid, changed the fuel filter, air filter, plugs, intake gaskets etc. All the usuals when buying a used Bimmer.

Sorry for the novel-like post! Anybody with the patience to read it I hope will have some advice, experience with this.

Thanks in advance!

-Ben "BMWTEK"

[X5 Meister]

Have you read about 'the lurch' ? Common problem. No clear remedy.

[imola38]

No, I haven't but I'll search that. This problem occurs probably more between the 2k-3k rpm range more so than anywhere else. Thanks for reading my long post!

-Ben

[X5 Meister]

Do a thread search and you'll find a lot of info on transmission issues, particularly the ones you describe above. Here is also a good read:

Jaguar S-Type ZF Gearbox Lurch fault

[Weasel]

Eh, I've read much longer posts than that just in the politics section.

As a fellow BMW tech with a 4.6is at 97k miles I understand what you're talking about. I think what you are feeling with the acceleration is the VANOS kicking in as it seems to do it pretty suddenly on the 4.6is for some reason. It felt so much better for the first couple weeks after I reprogrammed the DME and cleared tranny adaptations last year. (used latest version of progman as ista was too unreliable on older stuff at that time)

Being a BMW tech (or are you at an independent?) you could try that first to see if it makes a desired difference. If it does maybe consider the dinan software as it should open the VANOS solenoids earlier and under slightly less load making the power jump seem smoother.

As for the tranny, I usually don't see that issue on the 4.6is as much as any other model because of the beefed up internals etc. But if you clear tranny adaptations then drive pussy-footed for a day or so it may help clear it up a bit, if not it might be more mechanical than control in nature.

[c4racer]

my trans occasionally has a hard downshift into first, but it only happens on maybe 10% of stops - seems to happen more often with very slow braking - when you brake hard, it almost never happens. I don't bother running in manual mode to avoid it because it doesn't really bother me and doesn't occur all that often. Seems like a programming issue to me because certain specific conditions bring it out. Probably the Dinan trans tune would cure it, but otherwise I love how the trans works, so it is something I am willing to live with.

I don't really notice the non smooth take-off - is this under light throttle, medium throttle, 3/4 throttle? My 4.6 is a super smooth operator under just about any situation. I think the 4.6 motor and the Alpina tuned ZF is one of the best drivetrain packages in any car or truck I have ever driven. Close second is the Nissan Titan, but that is a very different animal - but put that motor in a mid sized SUV with some fat tires and responsive chassis and you would have something. Oh wait - no need, we have something in our X5 4.6is models already!! Cheers!!

PS - mine has 108K on it, 13K of those put on since I got it.

[Weasel]

I never really have the harsh downshift... maybe 1% of the time as I did get a mild case of it once after a long highway drive with truck and trailer loaded down. (after unloading truck and trailer) But not really since then.

[jst2878]

Clean your throttle body and your MAF sensor. Two easy things to do.

[imola38]

Thanks for the replies guys. I failed to say that I have researched 'the lurch" issue extensively I just didn't know that's what it was called.

Weasel- Thank you for the technical reply and it at least eases my mind that someone else has experienced this. I was a dealer tech for about 5 years but now I work at an independant, basically a sub-contracter for the shop itself as i'm the only factory trained BMW tech locally here.

I do have GT1 with Progman which is about 2 years old. I reprogrammed with this but I'm sure it's not the latest version. I may give the Dinan a try if I can find it to be worth the 3-400 bucks...

Since your intimate with your ride I have a couple more questions.

-What tires are you running?

-Do you have any squeaks or rattles? Especially from the rear gate?

Thanks in advance!

-Ben

[JoshGM]

Originally Posted by c4racer

my trans occasionally has a hard downshift into first, but it only happens on maybe 10% of stops - seems to happen more often with very slow braking - when you brake hard, it almost never happens....

Exactly like mine, but just like you I dont really get bothered by it!