PDA

View Full Version : Stumbling on hard acceleration



adb1028
02-18-2011, 07:33 AM
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
02-18-2011, 07:35 AM
Vanos would be a prime suspect for me.

Had yours had the DME update?

jjcools
02-18-2011, 07:59 AM
Does it feel like your clutch is slipping?

Vanos would be guess #1

danewilson77
02-18-2011, 08:12 AM
Try to move.....from a stop.......in 6th gear. If you can...it probably isn't the clutch

adb1028
02-18-2011, 08:23 AM
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
02-18-2011, 08:32 AM
Whistle could very well be the boot. Certainly would contribute to your acceleration problem as well.

Linh
02-18-2011, 08:42 AM
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
02-18-2011, 08:51 AM
Torn intake boots would, however, most certainly cause a lean condition, therefore, most certainly prompting a code and SES light.

kayger12
02-18-2011, 08:53 AM
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
02-18-2011, 08:54 AM
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
02-18-2011, 09:00 AM
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
02-18-2011, 09:42 AM
Is there a way to check the lower intake boot without taking it apart?



Sent from my DROID2 using Tapatalk

kayger12
02-18-2011, 10:15 AM
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
02-18-2011, 10:17 AM
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
02-18-2011, 10:48 AM
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
02-18-2011, 11:28 AM
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
02-18-2011, 11:32 AM
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
02-18-2011, 11:41 AM
http://img822.imageshack.us/img822/9190/20110218143217432.jpg

this could be a problem:blink

kayger12
02-18-2011, 11:44 AM
Lol-- Yep-- that's where they tear. Nice find.

That'll definitely get rid of your whistle.

danewilson77
02-18-2011, 12:53 PM
While in there you should clean your ICV, inspect your disa....

Sorry for the late reply.

adb1028
02-18-2011, 08:46 PM
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
02-18-2011, 08:48 PM
I like the Shark from everything I've read-- and the fact that it's possibly in my car...

pyreguy
02-19-2011, 10:59 AM
I'm happy with the Shark


Sent from my iPhone 5 using Tapatalk

adb1028
02-19-2011, 09:41 PM
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
02-20-2011, 04:12 AM
Now you're talking.

adb1028
02-20-2011, 02:23 PM
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.....