Stumbling on hard acceleration

[adb1028]

Just like the title says, on hard acceleration, the power delivery isn't smooth like it should be. It's really herky jerky (its almost like the tires lose traction then regain it). It feels like the car is tripping over its own feet when accelerating. Power below 3k RPMs is pretty weak and when you hit 3k it kicks in, albeit not smoothly.

At first I thought it was from the cold weather, but now its around ~60 degrees outside and its really getting on my nerves

Any thoughts?

[kayger12]

Vanos would be a prime suspect for me.

Had yours had the DME update?

[jjcools]

Does it feel like your clutch is slipping?

Vanos would be guess #1

[danewilson77]

Try to move.....from a stop.......in 6th gear. If you can...it probably isn't the clutch

[adb1028]

As far as I know, the DME has never been updated. I'm still waiting on BMW of Manhattan to send me the PO's maintenance records :facepalm

The clutch feels fine, I don't think its slipping. I did the test where you go 30mph, put it in 6th and floor it. RPM's didnt shoot up, they just gradually climbed as I gained speed, so I think the clutch is OK.

VANOS is my prime suspect also. I never noticed how loud it was until I was able to drive with my windows open yesterday, its actually pretty embarrassing how loud it is. Another thing I noticed when I had my windows open was a high pitched whistling sound when accelerating at low RPMs (I'm thinking torn lower intake boot?). Maybe the VANOS, DME, and this whistling are all related?

Thanks for the help fellas.

[kayger12]

Whistle could very well be the boot. Certainly would contribute to your acceleration problem as well.

[Linh]

Torn intake boots, Vanos, and DME can all create that bogging/hesitation through the power band. The whistling sound however, is usually traced down to a torn lower intake boot.

[danewilson77]

Torn intake boots would, however, most certainly cause a lean condition, therefore, most certainly prompting a code and SES light.

[kayger12]

Mine was weird on the 325 though, Dane-- I had just enough of a tear to get a high RPM whistle, but never threw a code--
leaning it a little, but just short of lean enough to trigger it I guess.

[danewilson77]

Mine was weird on the 325 though, Dane-- I had just enough of a tear to get a high RPM whistle, but never threw a code--
leaning it a little, but just short of lean enough to trigger it I guess.

Did yours stumble and drive like poopy?

[kayger12]

The boot only gave me a whistle, not enough to effect the engine noticeably.

When my Vanos was bad though, it bogged down low in the band and stalled with the AC on.

[adb1028]

Is there a way to check the lower intake boot without taking it apart?



Sent from my DROID2 using Tapatalk

[kayger12]

You can try to feel around for a large hole or get a mirror in there, but in reality it is really tough to see a crack or small tear until you have it off.

The boots are pretty cheap and you'll have to replace it eventually anyway-- if you want to pick one up and head down to my place, we can bang it out in no time.

[danewilson77]

Is there a way to check the lower intake boot without taking it apart?

Sent from my DROID2 using Tapatalk

You can by stuffing your hand in there and feeling around for a hole in both locations.

It is just better to buy one and replace.

Sent from my Droid using Tapatalk

[adb1028]

Just went to the dealer and picked up the boot, also picked up some MAF cleaner at Advanced Auto and got my codes read. Nothing came up.

Thanks for the offer Keith, I'll try this myself but if i need help I will contact you. PM me your address and I'll see if I have enough time to get down there today.

EDIT: Is there anything else I should do while I'm in there?

[kayger12]

Ok-- I'll PM you my address and my cell.

It's not hard to do-- you can just cut the lower boot off instead of struggling with the hard to reach screw on the hose clamp.

Give me a shout if you hit a wall.

As far as the MAF, does anyone else have an opinion on cleaning the MAF? I've read that it's not a good idea to do if it's not causing any problems. DW?

[Mtnman]

I hit mine with maf cleaner when i was in there changing the boots. But i just sprayed it and reinstalled. as directed. No problems to report 1 yr later.

[adb1028]

http://img822.imageshack.us/img822/9190/20110218143217432.jpg

this could be a problem:blink

[kayger12]

Lol-- Yep-- that's where they tear. Nice find.

That'll definitely get rid of your whistle.

[danewilson77]

While in there you should clean your ICV, inspect your disa....

Sorry for the late reply.

[adb1028]

The whistling is now gone idle seems a bit smoother.

Next on the list is a DME update, then that pesky VANOS.

What software should I got for?
-OEM (I assume 1/hr labor so lets say $150)
-Shark Injector ($350)
-Dinan Performance Engine Software ($299)

[kayger12]

I like the Shark from everything I've read-- and the fact that it's possibly in my car...

[pyreguy]

I'm happy with the Shark


Sent from my iPhone 5 using Tapatalk

[adb1028]

Reduced throttle lag is a big selling point for me on the Shark vs. OEM, and the extra HP is nice too. I might just pick up that BMW Performance intake to go along with it :eeps

[kayger12]

Now you're talking.

[adb1028]

Active Autowerke also has a tune. Power increase is 15hp and 12 ft lbs of torque, and its only $50 more than the Shark. Hmmmm.....