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Old 12-18-2007, 12:03 PM   #66
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Join Date: Aug 2006
Location: New Brighton MN
Posts: 5,018
My Ride: 2000 E46 with 254K
Originally Posted by Rajaie View Post
I seriously doubt a new CVV valve will resolve the vanos cold engine start idle problems. I have a new CVV with new hoses. Iíve performed lots of seals testing. When I have old seals (pistons) I get the idle problems. When I have new seals I donít have the idle problems.

Fuel injector cleaner has been known to temporarily solve the idle problems. Buna O-rings are susceptible to many harsh chemicals. These chemicals will cause the O-rings to swell. This swelling will initially act beneficially. The vanos Buna O-rings have significant compression set, flat top and bottom surfaces, and shrinkage. The swelling will increase their size and cause them to provide better support and seal to the Teflon seals.
But this is all temporary. The presence of the fuel injector cleaner will diminish, and the O-rings will lose their swell. The injector cleaner will have acted determinately on the O-rings. It will have dissolved from them the components that give them their elasticity. Thus although there is temporary improvement, the end result will be the hastening of the O-ring demise.

The DME utilizes the vanos to help heat up the cats faster on cold engine starts. It is at this time that the idle problems occur due to the failing vanos.
The DME does not perform this vanos maneuver immediately at startup. It waits until the engine warms sufficiently to handle the vanos (timing) maneuvers. Thus the colder the temperature, the colder the engine, and the longer the engine needs to warm up before the DME performs the vanos maneuvers.
It might be that you are not waiting long enough to allow the engine to warm up to the point where the vanos is used to heat up the cats. When the car is driven the idle problems donít occur, unless the car soon comes to a stop and idles again.
I have to ask where you get this info because the vanos has no effect on the catlist warm up. They use overlap from the vanos to control NOX when the car is running they uses secondary air to WARM up the cats. i know you have identified and issue with these cars but you seem to put all the blame on the vanos(yes it does cause alot of issues) However the Crank vent valve can cause cold start issues. Software can cause cold start issues and so can a failing fuel pump or 3/2 valve and even the MAF(no disconnecting it is not a valid test). The Crankcase vent valve when they fail cause an internal air leak that cause the computer to add way to much fuel and can cause stalls check engine lights or worse. So while the vanos is a REAL issue it is not the only thing. Please properly diagnosis the car before throwing parts and causing to the wind.

Seth Thorson
Service Manager/BMW Tech
JB Eurotech Service "Your Reasonable Dealer Alternative"

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