2004 BMW 325i E46 M54 ready to blow it UP

[Rickt1962]

My car might be old but only has 120,000 miles on her.
I live in Pennsylvania where Emission with Check engine light can be a NIGHTMARE ! I only have a small rough idle in the beginning when cold and just turn off the engine and it clears up perfect.

Before taking my car in for inspection I have check engine light and after reading the CODE it was P0174 which I call it the 12 days of Christmas Blues

This is the first time I ever took any Vehicle in for Inspection I always did the work my self....... But I gave up and the Shop Has know CLUE !

Since it has 120k on her I put in new plugs , new coils , Air filter, Cleaned the MAFF sensor found a crack on the boot replaced it.
Air Intake Manifold Flap Adjuster Unit Disa Control Valve was melted a little so replaced it.

Took off the Idle Control valve cleaned it and ripped the old hose so that was replaced

Went ahead and replaced both 02 sensors bank one and two Hey got over 120k on the original.

Found some moisture in the Air pump so replaced the Secondary Air Injection Check Valve also clean the other MAFF sensor after the Air Pump aka SMOG.Smoke test at 6 psi didnt show anything.

No leaks in the exhaust or CATS not clogged I have all the power in the world driving.

Thought it might be the gas cap throwing that code but the engine runs rough for a short time I don't think a gas cap would be it.

I just know ITS GOING TO BE something STUPID !!!


HELP anyone have any other Ideas to check ? Driving a month past do for Inspection and the garage has no clue .

I hope this is in the correct section of the FORUM

[shadowpuck]

a lean code.....

i'd start with a smoke test with a smoke machine capable of building pressure...
in general, p codes are quite unhelpful on bmws, but, a lean code is pretty obvious.

i'm rather surprised a qualified bmw shop couldn't fix it - rather common issue...

[Rickt1962]

I posted the smoke test at 6 psi with nothing to show for it

[shadowpuck]

it was unclear in your post what exactly you smoke tested? did you check the entire intake tract?

have you looked at any live data (especially related to the MAF sensor)? have you checked the injectors? have you scanned the car with a bmw specific code reader?
since you've replaced parts and such have you retested with a smoke machine?

what did the shop do? is it a bmw shop?

[dworthy]

+1

BMW's are very sensitive to vacuum leaks. The smoke will go out the largest hole it finds first. Once the hole is fixed, you have to get another smoke test done, aka wash rinse repeat.

[Rickt1962]

+1

BMW's are very sensitive to vacuum leaks. The smoke will go out the largest hole it finds first. Once the hole is fixed, you have to get another smoke test done, aka wash rinse repeat.

Thanks guys I printed this off and heading back to the shop with it.

[bmwdirtracer]

Shops just LOVE to hear a customer say "I heard it on a forum", much less have them wave those replies at them.

You'll find that a technician, or even a service advisor, will be more likely to give at least a tiny bit of credence to your information if you present it in a more acceptable manner -- like, "my brother, who is a master BMW technician, advised me that I need to visit a BMW specialist shop, and ask them to continue further diagnosis of my issue, including reading BMW specific codes, smoke testing the entire intake/ccv system (not just the secondary air system) to make sure we've fixed all the leaks, perhaps send the injectors off for testing and ultrasonic cleaning, testing the fuel pressure, crankcase vacuum, etc.,etc.,etc.

Seriously, if you walked into your generic shop and waved pages from a forum, you will never be taken seriously again at that shop. Which is fine, because you needed a better shop anyway.