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Discussion Starter #1
I've been fighting a rough idle issue on my 2000 328i for the last 4 months. The funny/sad thing is, I've owned the car for only 5 months. Back when I bought the car, it had a cold start idle fluctuation, so I immediately replaced the vanos seals.

About a month later it began idling rough again (when both cold and warm). The cold start idle would throw misfire codes on cylinders 2 and 5 along with an evap leak code after about 2 minutes of idling. I took the car to a bmw mechanic for diagnosis and an oil change. He recommended changing the spark plugs, fuel filter, and fixing a vacuum leak (back of intake manifold -> secondary air pump). I did all three, but nothing changed.

After extensive research, I made the decision to replace the entire CCV system with the cold weather equivalent. I had to modify the cold weather CCV in order to run the vacuum line from the CCV through the insulating foam, and up to the fuel rail. When replacing the CCV, I noticed that the original vacuum line running from the CCV to the fuel rail was broken. After everything was put back together, the idle was still the same.

Yesterday when I started the car cold and left it to idle, I no longer had misfire codes for cylinders 2 and 5. Now I have codes p1477 & p1478. p1477 means the leakage diagnostic pump reed switch did not open, while p1478 indicates that there is a small leak in the fuel evaporative system. This leads me to believe that there is a leak between the fuel system and the intake manifold.

When I get home from school, I'm going to check the top of the fuel rail, back of the manifold, and fuel filter for any potential vacuum leaks. Any additional locations I should check? Any other thoughts as to what the issue may be? Has anyone else had this issue? I'm determined to solve this idle gremlin.

Thank you!
- Patrick
 

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I believe the elbow bend on the back of the intake manifold...next to the line coming from the aft side of that black/white valve...might have dropped off. You may be able to reach in and get it back on without moving much, but I believe you'll need to remove the panel in front of the brake booster.

See realoem.com for fuel preparation (I think)

Hope that's it. If not, something else to consider. The ccv on the 328i has a plug on it in the front and doesn't take a vac line. Could you have maybe put on the line that should have gone to intake mani onto the ccv?

You should have a plug on your ccv port (in the front beneath the insulation)...as far as I know. I'm a '99 328i and that's what I have.
 

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Discussion Starter #3
I was thinking the same thing with the elbow bend. I'll check that when I get home.

As far as the plug on the front of the CCV goes, my original CCV had a vacuum line that went to a hard-line on the fuel rail, and then to the fuel pressure regulator. The new CCV came with a rubber block-off underneath the insulation which I removed, in order to fit the new vacuum line. The additional port on the back of the intake manifold that you are talking about is blocked off with a piece of rubber, similar to the rubber block-off that came on the new CCV.

If the elbow bend is still attached, I'll try blocking off the end of the vacuum hose from the front of the CCV and removing the block-off on the back of the intake manifold to attach the vacuum hose from the FPR.
 

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2000 328i MT
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Have you checked if your oil filter housing gasket is leaking? Chances are that it is (they all eventually leak). It can be a major source of vacuum leaks. I have the same car and until I replaced my leaking gasket AND the CCV system and alI vac lines I had issues with cold start idle and cold stalling. Since then no such issues and I haven't done the VANOS rebuild as of yet.
 

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Discussion Starter #5
With all this spare time on my hands, I've decided to revisit my cold start misfire issue. Funny enough, dmax was right. The elbow on the back of my intake manifold was off. I ended up reattaching the elbow to the back of the manifold and using a ziptie to hold it in place. While it did fix the codes p1477 and p1478, it unfortunately brought three new codes into my life. These codes are p0305 (misfire, cylinder 5), p0302 (misfire, cylinder 2), and p0456 (minor leak, 0.5mm). These codes are triggered during cold start. The longer I go without driving the car, the worse it is.

I recently bought a smoke machine off of ebay to make sure I had no vacuum leaks. Hooked it up to my car and no leaks anywhere. What could be causing this issue?
 
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