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My 2004 330i ZHP with about 75,000mi encountered some difficulties this winter when it was cold and snowy. Symptoms were a rough idle, hesitation, and reduced power. I don't have a long commute and it was parked outside, so I suspect a CCV issue.

The car did pop a SES light with codes P0171 and P0174, but I suspect these were due to a leaky DISA valve seal (found with carb spray). When I pulled out the DISA, the flap was wet with an oily substance that smelled strongly of gas. I cleaned the valve and used RTV to seal the vacuum leak. After clearing the SES code a few weeks ago, it hasn't come back.

Since these incidents, I have noticed reduced MPG (at least 3 MPG lower) and it seems slower (it also has a VANOS rattle, but I think that's a separate issue). I tested the CCV this morning by detaching and blowing into the crankcase vent tube. There was no resistance (is this normal?!), but if I blew enough volume of air I could hear a bubbling sound, suggesting that the valve is now okay(?).

So here's the question: should I replace the CCV (with the cold weather version)? I suspect it was stuck (open?) for a little while and squirted blowby into my intake, thus wetting the DISA and fouling my spark plugs. But the CCV valve seems to have returned to normal operation now that it's no longer cold here. I don't want to put in new spark plugs just to have then fouled again, but I do now park in a garage. I know the CCV is a PITA to replace and I don't want to replace a part that isn't broken. What would you do? Thanks!
 

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One thing you can do is put some plastic wrap over the oil fill cap and see if there is suction or not.

Does the car smoke from the exhaust when it's cold? Does the oil fill cap have yellow sludge? Do you hear some weird honking sounds? I'd check for any oil leaks in that area.
 

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Hey solidjake - thanks for the quick reply, I love your DIY vids. I have lots of suction at the oil fill cap and at vent hose from the crankcase to the CCV. The idle changes slightly when I remove the oil fill cap too. I see no current symptoms of a CCV problem: it's not honking, smoking, and doesn't have the indicative mayo. I've been keeping an eye on the oil level, and it seems okay. I wish I had tested it back in the cold spell.

I'd actually be much better if it was displaying CCV symptoms because then I'd replace it and move on. It is possible for a CCV to fail during a brief cold spell and then return to normal (or at least what seems to be normal)? Should there be any resistance when I blow into the CCV from the crankcase? Is it okay that my DISA (and intake near the DISA) were wet with blowby-like fluid? Would fouled plugs lead to my symptoms of reduced power and gas milage?

I'll take a look at my plugs this afternoon following your DIY, of course. If they do appear to be fouled (although I'm no expert), should I be concerned about the same thing happening to the next set of plugs if I don't replace the CCV? Also, should I try to clean the blowby-like stuff from the intake manifold or just let it be?

Thanks again, really appreciate the advice!
 

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Intake manifold removal/ gasket replacement for code:p0171/P0174

I've been searching the entire web for pictures about how to perform this heavies jobs on my: (2001 BMW X5 4.4i M62) but unfortunately no body seems taking their chance to do this type jobs. Amazingly! I came across of: E38 BMW 740i/iL M62 Intake Manifold Removal

which is a link showing you how to do the same job, but on a different BMW models. However I have to say thanx to the guy who has posted these pictures on the web because by following them I was able to succeed and also saving me:$ 3,265 dollars jobs in labor. Please don't get me wrong! the entire job cost me:$405 dollars, only because my car was due for tune-up service and this is a perfect time for me to do everything at once. But some parts are not pictured.
Because the procedure of the intake manifold removal, replacing all the gaskets: rear, front, under the intake took me about: 8hrs job.

See pictures below for details....

How to resolve a Learn condition with code: P1158/P1160/P0171/P0174
In order to remove the intake manifold, we will need to remove the plastic engine/cylinder cover, (unhook the injector's clips are the most part on this job, otherwise remove the throttle body and the top fuel rail together with the injectors are easy. You may used 2 markers with different colors just to identify certain plugs. Certain BMW's model are much different than other because I found the job more easy on my car than E38 model explained.

(REMEMBER THIS WAS ON A: 2001 BMW X5 4.4i M62)

I hope this helps for some of you... Because The $tealers will charge you $$$Thousandsss of dollars to get to this point, now you can do it for free. At this point, you can clean out the intake manifold, intake valves, the fuel injectors, replace the back plate of intake manifold just like I did! Good luck! And for those who need to replace the valley pan gasket, you will need to remove the water pump and take out the center "cap and seal" part... However I do not mess with it and mine looks ok, once I do not have any leaking antifreeze under the vehicle.

Be careful on the gas pedal when testing the car later, because as the engine notice there is no more vacuum leak, the compression now build-up inside the entire intake system pushing his way back normally through the muffler now, which resulting the car to take-off like a jumbo airplane.
 

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code:p1158/1160 P0171/P0174 fixed solution!!!

How to resolve a Learn condition with code: P1158/P1160/P0171/P0174
In order to remove the intake manifold, we will need to remove the plastic engine/cylinder cover, (unhook the injector's clips are the most part on this job, otherwise remove the throttle body and the top fuel rail together with the injectors are easy. You may used 2 markers with different colors just to identify certain plugs. Certain BMW's model are much different than other because I found the job more easy on my car than E38 model explained.

(REMEMBER THIS WAS ON A: 2001 BMW X5 4.4i M62)

I hope this helps for some of you... Because The $tealers will charge you $$$Thousandsss of dollars to get to this point, now you can do it for free. At this point, you can clean out the intake manifold, intake valves, the fuel injectors, replace the back plate of intake manifold just like I did! Good luck! And for those who need to replace the valley pan gasket, you will need to remove the water pump and take out the center "cap and seal" part... However I do not mess with it and mine looks ok, once I do not have any leaking antifreeze under the vehicle.

Notes: if you've tried many other options by ordering alot of parts and nothing seems to resolve your vacuum leak, than you definitively have to visit a mechanic shop for a smoke test. This was my last options by having my entire intake manifold tested for:$60 and found out whole much smoke was coming from: under the intake manifold gasket from the front corner driver side.
 

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