1500RPM surge?

gregorio · #1 09-20-2010, 07:04 PM

Hi everyone - wouldn't you know it? I just paid the transfer fee, registration and sales tax today and on the way home, I notice a surge or stumble at 1500RPM (37MPH in 5th) at steady cruise. It is almost as if fuel was being cut but there is NO dip in RPM. I just had it smogged and there were no codes.

Anyone hear about this?
Greg

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mgbmwx5 · #2 09-20-2010, 08:24 PM

Quote:

Originally Posted by gregorio

Hi everyone - wouldn't you know it? I just paid the transfer fee, registration and sales tax today and on the way home, I notice a surge or stumble at 1500RPM (37MPH in 5th) at steady cruise. It is almost as if fuel was being cut but there is NO dip in RPM. I just had it smogged and there were no codes.

Anyone hear about this?
Greg

It sounds like a dirty fuel filter.

gregorio · #3 09-21-2010, 11:24 AM

Dirty fuel filter? Wouldn't that be more apparent at higher RPM and greater amounts of throttle? It seems to have good upper RPM performance but I have not really pushed it past about 4500RPM. The performance does seem a little soft on the bottom but I was thinking it was caused by the transmission upshifting so fast.

mgbmwx5 · #4 09-21-2010, 11:51 AM

Quote:

Originally Posted by gregorio

Dirty fuel filter? Wouldn't that be more apparent at higher RPM and greater amounts of throttle? It seems to have good upper RPM performance but I have not really pushed it past about 4500RPM. The performance does seem a little soft on the bottom but I was thinking it was caused by the transmission upshifting so fast.

How many miles on your X5?

mgbmwx5 · #5 09-21-2010, 11:54 AM

It hits 5 gear at 37 MPH?

Jordo · #6 09-21-2010, 01:37 PM

I have the exact issue you do! and funny enough, I noticed it at the same time! On the way home after buying it!

I asked this same question. Read this thread completely. It should shed some light on it.

http://www.xoutpost.com/bmw-sav-foru...ause-pics.html

EDIT: what you called a "surge" I called a "mis-fire". Just a FYI.

gregorio · #7 09-21-2010, 08:50 PM

Jordo - did replacing the hoses fix your problem? I really don't know what to call it; surge, misfire, stumble. It feels like the vehicle is being jerked from behind for a split second every 4-5 seconds. It is not a typical engine misfire where it runs on 7 cyls for a few seconds and clears. It happens around 35-37 MPH and 1400-1600RPM in 5th. Yes, it shifts into 5th in DRIVE or I can force it by pulling the lever over in MANUAL.

My mechanic said it threw a CYL8 Misfire a few times and he found water in the spark plug/coil area. The engine was steam cleaned a few days ago so this was a likely cause. No other codes were found after blowing out the water but it did not solve the problem.

The only thing we can find at this time is that the transfer case has a 0x1E4154C8 54C8 Classification Resistor code that cannot be cleared. Could that have anything to do with it?

The car has 88,000 miles on it and has been maintained by the dealer until 50K and then by an independent BMW specialist here in the South SF Bay Area.

Thanks everyone.
Greg

Jordo · #8 09-21-2010, 11:04 PM

Quote:

Originally Posted by gregorio

Jordo - did replacing the hoses fix your problem? I really don't know what to call it; surge, misfire, stumble. It feels like the vehicle is being jerked from behind for a split second every 4-5 seconds. It is not a typical engine misfire where it runs on 7 cyls for a few seconds and clears. It happens around 35-37 MPH and 1400-1600RPM in 5th. Yes, it shifts into 5th in DRIVE or I can force it by pulling the lever over in MANUAL.

My mechanic said it threw a CYL8 Misfire a few times and he found water in the spark plug/coil area. The engine was steam cleaned a few days ago so this was a likely cause. No other codes were found after blowing out the water but it did not solve the problem.

The only thing we can find at this time is that the transfer case has a 0x1E4154C8 54C8 Classification Resistor code that cannot be cleared. Could that have anything to do with it?

The car has 88,000 miles on it and has been maintained by the dealer until 50K and then by an independent BMW specialist here in the South SF Bay Area.

Thanks everyone.
Greg

Greg,

I finished replacing the hoses for the oil seperation system. I then went out and drove my X for at least 25 mins.

I COULD NOT GET IT TO surge, misfire, stumble... what ever you wanna call it! I will say this tho. It was a Royal pain in the ass to get to the lower hose end. But so far it seams worth it.

I notice an over all smoother running, at lower RPM's then before. No noticable power increase, but I feel its def smoother, and best of all no stumble.

Do you notice any oil at the back of your motor, if you take the top cover off? The way I understand this system, is it takes the crankcase pressure, which is full of a oil vapor/fine mist, and processes it into a collector, which dris back into the crankcase. But the "air" is put directly into the intake manifold. If it is not hooked up, it is sucking raw air into the system and, which is "unaccounted for", and causes a misfre, stumble, surge.

I hope that helps. The first thing I would do is look for riped, damaged hoses on this system. Refur to the link I provided to see the location.