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Thread: p0491 p0492 Secondary system issue.

  1. #1
    Join Date
    Mar 2016
    Location
    Las Vegas
    Posts
    4
    My Cars
    2000 BMW 540i

    p0491 p0492 Secondary system issue.

    Wsup guys! I need your help.
    I have a 2000 BMW 540i.
    Recently the vehicle has developed the P0491 and P0492 codes.
    (I checked the codes before the rough idle and right after I check it rough idles the next day... go figure.)
    When warm the car has a rough idle and I wonder then why it has anything to do with the secondary air system.
    (Does it? I assume so because the codes say so, but some times things can be a little tricky.)
    --I have put Sea Foam into the system (before the valve) and it only goes through the system at start up, so I know the pump is working. Smoke plumes out during the warm up period, but none after. Does this sound like the secondary system?
    --Sorry, the way the valve is set up, I can not check to see if the valve operates correctly. If the valve is stuck open, would the vehicle idle rough? If it were stuck closed then there would be no smoke during the warm up stage right? Just trying to narrow down the part I need to replace so that I am not wasting money. Thanks ahead of time for your help. Not many threads for a 2000 BMW 540i. I am not even sure where to put the sea foam if I were to be trying to clean the rest of the system of carbon with out depending on the secondary system.

  2. #2
    Join Date
    Mar 2016
    Location
    Las Vegas
    Posts
    4
    My Cars
    2000 BMW 540i
    By the time I get any help here I will have found my own answer. Thanks for nothing. I'll try a site that will help.

  3. #3
    Join Date
    Mar 2003
    Location
    St. Joseph, Mo.
    Posts
    3,000
    My Cars
    95 m3+, 03 ZHP, Mk4 Tdi
    well, gee, i didn't realize you had purchased premium support! let me jump right on this!

    ummm. well, p0491 and p0492 codes - first, p codes are very unreliable when troubleshooting bmw's. that said, sometimes it's all you have.

    secondary air systems shouldn't specifically cause a rough idle when warm. the secondary injection system only functions for a brief period of time when temperatures are below 40 degree F (i think that's the right cutoff) at startup.

    that said - rough idle is more than likely caused by vacuum leaks - both intake and exhaust side. the troubleshooting step when leaks are suspected is to perform a smoke test with a professional smoke machine. repair the leaks, then test again.

    at the likely mileage of this vehicle, you didn't tell us the mileage - the engine likely has several leaks, and the crankcase pressure should be checked as well to ensure proper operation of the CCV system.

    i did a google search and found tons of hits - this is a really common issue....i'm sure you've done some searching already, but if you look at bmw 540 p0491 p0492 then you'll find several helpful posts here and elsewhere.

    the bmw software has a test process for checking the secondary air system.

    finally, a note, i get it that you wanted a response to fix your problem (we all hate it when our cars act up), but all of us do this in our spare time. sometimes, posts get missed - get over it.
    '95 325iS - auto to manual swap done!

  4. #4
    Join Date
    Mar 2016
    Location
    Las Vegas
    Posts
    4
    My Cars
    2000 BMW 540i
    Oh gee, I didn't realize there was a premium support available! Let me pull out my credit card.

    Umm, well, resolved it in a forum that is not dead.

    Thanks for your day late and dollar short response.

    Finally, a note, a forum that responds days later is a day late. How well used is my time if day by day I check with no response... How do I know there will ever be a response... Meanwhile my care issue needs to be resolved asap. I will ask for help and be told to wait until when unless I pay... Believe me, I got the help, quick, free and we all had fun resolving the issue. ==get over this sorry sight.

    - - - Updated - - -

    This sight was too stupid to allow me to recover my login info with out a 15 minute lock out. There is no doubt why this site never has a car issue resolve listed in a search. No clear answers, no report of resolution.

  5. #5
    Join Date
    Mar 2003
    Location
    St. Joseph, Mo.
    Posts
    3,000
    My Cars
    95 m3+, 03 ZHP, Mk4 Tdi
    *laughing*

    someone still thinks this is a business or something.....

    complaining about a site's lockout procedure - that's one of the funniest things i've read all day. glad you are able to get your car fixed....

    this is one of the funniest post i've read in a long time - thank you for posting!
    '95 325iS - auto to manual swap done!

  6. #6
    Join Date
    Feb 2015
    Location
    London, United Kingdom
    Posts
    1,184
    My Cars
    E36 328is, E87 116i
    Why you acting like anyone owes you anything ? I've been active in this thread and sometimes have my posts missed or ignored.. you've come from nowhere and expecting people to attend your problem ? Sorry mate there's no mechanic ambulance here... just a bunch of friends who are pro's and techs who offer their advise and help FREE OF CHARGE. Yes that's right FREE OF CHARGE! If your expecting some sort of instant reply or fix for your car warm up your credit cards and find a pay to repair service somewhere. I personally don't welcome ignorant and rude people such as your self that come here with a stinky attitude demanding instant replies.
    C217 S63 AMG S Cabriolet ( Daily )

    E87 116i with mild cams, headers, cold air intake making 136 bhp Lol (My Learning Track Car)

    E36 328i Sport ( Project in making and future race/track car )

  7. #7
    Join Date
    Jun 2002
    Location
    Aberdeen, NC (yes, again)
    Posts
    23,672
    My Cars
    E39M5, E500 4WD
    We're going to have to adjust the Dikfor Lockout System, if it's only holding for fifteen minutes. That was supposed to hold for fifteen YEARS, dammit.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  8. #8
    Join Date
    Dec 2004
    Location
    Huntsville, AL
    Posts
    25,923
    My Cars
    87 325is
    I agree with Chris. Now if I can just find that ban button...
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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