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Thread: A/C and Mis-Fire related? Does anyone have any idea as to what this is? Please Read!

  1. #1
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    A/C and Mis-Fire related? Does anyone have any idea as to what this is? Please Read!

    Hello all,
    I have been driving a 1999 323i which just hit 130k for about 3 months now and just recently started to use the A-C. when i bought the car it was in the winter and could not tell whether the A-C worked properly. with that said i have noticed that when I have the A-C on which works and comes out cool, but when i drive the car I get this horrible noise almost like a grinding or a baseball card stuck in the spokes of your bicycle tire.

    I didnt think much of it since the A-C blew cold and worked just had an loud but odd noise. Last week I had gone out and replaced the spark-plugs (NGK Platinum) and oil. After driving the car a week and with the weather getting above 90 The car began to miss-fire. I had the codes checked and it showed every cylinder was misfiring so i went back and checked all the plugs and took them all out to see if i had made a mistake. I didnt find anything wrong with them and put them back in.

    Ok so here is where the odd thing comes into play here . My father wanted to see what was going on with the A-C thinking it was directly related by having the A/C compressor putting to much stress on the coils causing the miss-fire. But after he had taken some kind of sprocket off (not really sure what he did since i wasn't with him at the time) of the compressor and put it back on He decided to test the car out.

    Now the A/C no longer works and the car no longer miss-fires at all . When i got home I checked thinking he released the pressure from the system and it needs a recharge but when i checked the pressure it showed it was at critical.


    So now this brings me here to the forums, hoping that someone within the forum has had this happen or has had experience with this sort of problem. Otherwise I'll have no choice but to bring it to a mechanic to fix.



    Sorry about the length of the problem just wanted to make sure I got everything in that you all will need to know in order to diagnose.

    All input is appreciated. Thanks in advanced

  2. #2
    hooRAH is offline Certified Ziptie Mechanic
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    Did you use the correct plugs for this car? I know the correct plugs are NGK, but don't know if they're platinum or not. Probably not, and this is probably the cause of your misfire.

    There are no sprockets on an A/C system. Perhaps he removed the belt? Removing the belt would cause it not to work.

    If you check the low side pressure of the A/C system when the system isn't running, the pressure will be circa 100psi, which will appear to be critical if you're using a low-side-only auto parts store gauge.
    01 330Ci 5spd / 07 Honda Pilot EX-L
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  3. #3
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    When i was replacing the spark plugs. I made sure that as i was taking them out they were similar and the guys at my local import store assured me these were the plugs to use. I've heard you can use platinums or rubidium ones for NGK if you decide not to go Bosch.

    But why would the car run perfectly fine for a week and then send a misfire and put out codes would it do this right away if it was the wrong plugs?

    He did remove the belt but he put it back on. The fan will blow but doesnt come out cold. with whatever else he took out i can not be positive. and yes i believe i did check it when the A/C was not running so with that said i will go and see what the pressure is at.

  4. #4
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    The Pressure is still in the red at critical, although he allowed some of the pressure to be released and told me that he doesnt hear the noise anymore but i have to drive the car for a bit to find out. but even still the A/C still remains not working.

  5. #5
    hooRAH is offline Certified Ziptie Mechanic
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    I would stop making changes until you understand how these systems work. You don't want to vent off your refrigerant charge, its NOT overfilled. You need to understand how the low-side pressure gauges work. When the system isn't running, the static pressure in the system should read around 100 psi, which is normal. If you've dropped the static pressure to 40 psi (what the auto-parts store filler gauge would read as normal), you've released all of your refrigerant and will have to charge it back up before the system will work again. This is why you really need to understand what the pressures mean in an AC system before messing with it.

    Second, just because the auto parts store guy says the plugs are the correct ones does not make it so. Similar doesn't cut it. Some people run bosch platinum +4 plugs and have no problems, other people run them and get horrible misfires. We don't know why. What we do know is that the NGK plugs with the correct part number (don't know the whole thing, ends in EQUP I think) have the most reliable track record for not misfiring, so thats what most people use. Use anything else and you risk a misfire (or at least a misfire code).

    Is it possible that the misfire is caused by something OTHER than the plugs? Of course it is. On the other hand, theres no sense in making the problem more complicated by running plugs that are more prone to misfire.

    I can't see anything that would cause the A/C system running to cause a misfire, or the a/c system not running to cause the car to not misfire. Its most likely a coincidence.

    As for why the AC system used to work and now doesnt - I have no idea. Without knowing what you or your father took apart and put back together (which clearly is the cause as it was working before) I wouldn't know where to start aside from checking to make sure the clutch compressor is getting power when the AC is turned on.
    01 330Ci 5spd / 07 Honda Pilot EX-L
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  6. #6
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    My Father has the exact same car its a 2000 323i only difference is that his a/c works great and has 175k on it. apart from that no difference... with that said i pulled his car into the garage and checked his psi levels for the a/c they were lower then what my car had originally. with this said releasing some of the pressure was needed because now the a/c unit engages and works but does not make the odd loud noise... and unfortunately no cold air blows out.

    As far as the spark plugs go I have delt with the family owned import business for 4 years now not only with this BMW but with my previous 323i and my brothers 2003 325i. They assured me that they were the exact same plugs that i put into my previous car and ran great. I wont rule out their mistake, if that is the case but will make sure to check the part number.

    Think one of the coils could have gone bad instead? They are the original coils on the car

  7. #7
    hooRAH is offline Certified Ziptie Mechanic
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    Whats the high side pressure of your AC system?
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  8. #8
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    Something with your spark plug change has led to the misfires. Verfiy that plugs are NGK BKR6EQUP and are properly torqued down. Also verify that the coils are propely seated on the plugs, the electrical connectors at the coils are properly seated, and that the ground straps are securely fastened. By any chance were the codes for lean misfires?

    A grinding noise from the A/C compressor, assuming that's where it actually originated, is a very bad sign. Subsequent problems may or may not be related to tinkering by you or your father. The compressor is likely toast at this point, hopefully it hasn't contaminated the entire system although that is a distinct possibility.
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  9. #9
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    I verfied that plugs are NGK BKR6EQUP and they are properly torqued down. Also verify that the coils are propely seated on the plugs, the electrical connectors at the coils are properly seated, and that the ground straps are securely fastened.

    The only thing that he took off was the A/C belt and one of the caps behind the compressor that had a spring inside. It did not decompress the system though so after he put it back together checked the system as it was running and was at the critical point on the gauge. before releasing pressure he checked his on his 2000 323i and it said it was normal so at that point he went over to my 1999 323i and released some of the pressure which is now where it is supposed to be unfortunately this lead to the cold A/C to stop blowing out even though the system engages no problem, but seems to have gotten rid of the griding noise when the A/C is on as I am driving.
    Last edited by Raceman2244; 06-02-2011 at 02:43 PM.

  10. #10
    hooRAH is offline Certified Ziptie Mechanic
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    So the AC compressor clutch engages, the static pressure is near 100psi (system off), the low side pressure drops to around 35-45psi while running, and the A/C is not blowing cold?
    01 330Ci 5spd / 07 Honda Pilot EX-L
    Will read/reset SRS codes in South Florida for beer money


  11. #11
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    yes all of the above is correct ^

    Any other ideas?
    Last edited by Raceman2244; 06-02-2011 at 09:03 PM.

  12. #12
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    I have the exact same problen on a 99 323i.Car runs great until you turn the A/C on.That was until the compressor took a dive.Im a mechanic who works on these things reuarly.I just bought this car knowing it had a run issue.I've replaced everything.From plugs to coils MAF sensor,oi lserperator valve and all hoses can't find a vaccum leak either.I've spoke with a few people who seem to think that the vanos is acting up causing the car to run bad when a/c is engaged not allowing timing to be changed properly.Has anyone else seen the vanos issue before?

  13. #13
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    You can try replacing the vanos seals. http://www.beisansystems.com/procedu..._procedure.htm
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  14. #14
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    +1 on the AC compressor tango uniform. The miss-fire codes you were getting is from the engine ping/knock sensor that detects engine rattles and pings. As the knocks get louder the engine attempts to adjust the firing rate which results in miss-fires and codes. I had this problem with my a couple 100,000 miles ago and ended up replacing my AC compressor, because the bearings were shot and when this happens you have to replace the compressor unit. Just my two and a half cents worth.
    V/R Zachary Pullins Sr.
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  15. #15
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    Well the A/C compressor fixed my air and the misfire problem.I would've never guessed it but it did.

  16. #16
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    Had the same problem with my bimmer so I figured based on your symptoms that you were having the same issue. Glad I was able to help...
    V/R Zachary Pullins Sr.
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    2016 Cadillac SRX & 1999 E39 540i/Sport
    " Vision without resources is just hallucination"

  17. #17
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  18. #18
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    Zchild, that is the best answer and description of this problem that I have found. I believe the biggest problem is some of the cheap aftermarket compressors (that some are selling at full markup).

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