E39 engine rpms go down while idle,help!

[sorin3q]

hi everyone,when i'm turning the engine on and it's running in idle mode(not in any gear),the rpms go down and quickly back up, repeatedly ,its not affecting the ride ,but the engine light is on and the code is P1423 i searched and it appears to be the secondary air pump issue,i wonder if this rpm thing has anything to do with this code and air pump..????

[brandon5069]

I'd bet it has something to do with Vanos....

[sorin3q]

vanos? can you be more specific? i'm still learning bit by bit about bimmers..

[brandon5069]

The M52tu engine (the one in your car) is very susceptible to having the vanos seals deteriorate over time due to heat cycling and crap for material.

Bmw is aware and made a software update that band aides this problem.

There is an aftermarket manufacturer that makes a kit to replace the seals made of better material. (I think the name is beisan or something similar...)

Usually symptoms of vanos seal failure are seen during cold start idling.
-engine start
-RPM's stay elevated for a few seconds
-RPM's fall to normal level
-RPM's drops below normal level
-engine almost dies
-RPM's return to normal level
-RPM's drop again about 15-20 seconds later
-and this continues until car is warm.

During normal operation after warm the engine will run fine, but not at optimum performance. Poorer gas mileage is a result..as well as a moderate drop in power. Both of these hardly noticeably unless you've had the car since new.



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That said...
It could also be a vacuum leak, ccv failure, or clogged icv

[sorin3q]

thanks i got it now,so can i find just the rubber O rings ?how much will the labor cost,is it a preety complicated procedure for DIY?

[brandon5069]

Here you are...

http://www.beisansystems.com/

read up!

[pbonsalb]

You can DIY if you are patient and careful. It is far easier than installing Vanos on an older single vanos car since retiming is not necessary on the dual vanos M52TU. I did mine about a year ago.

[jamesdc4]

Listen to Brandon!

What is VANOS? (http://www.automotiveforums.com/vbulletin/showpost.php?p=773611&postcount=2)

Does my engine have VANOS/single/double? (http://forums.bimmerforums.com/forum/showpost.php?p=12432585&postcount=15)

What is the 52*i/530i double vanos problem? (http://bimmer.roadfly.com/bmw/forums/e39/7494631-1.html)

And, finally, the DIY...
Vanos/Double (I6) (http://www.beisansystems.com/procedures/vanos_procedure.htm)

[NewEnglandJason]

So us v8 guys dont have the Vanos??

[allamer35]

So us v8 guys dont have the Vanos??

Pre 98, no. Very fortunate. :buttrock

[NewEnglandJason]

I have a 98 though..... so no then right? Im a lil tired been up since 4am