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Thread: Intermittent slow acceleration - potential causes?

  1. #1
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    Intermittent slow acceleration - potential causes?

    Hey guys. I know a 528 isn't the fastest E39 but at suspense filled 20 seconds to get to 100kmph, something is really off. I had the codes read 3 weeks ago and got a code for the VANOS and a code for an air sensor. Both codes were cleared and just the air sensor returned, so I replaced that and things seemed better. However, now it's going really sluggish again but it happens intermittently, and sometimes it seems to figure itself out at higher RPMs.

    I don't fully understand VANOS but I do know it has to do with lower end power, though with no codes appearing again, I'm not entirely sure it's VANOS related. I'll also check for vacuum leaks but the intermittent nature makes me wonder if it's that either. Any thoughts on what it could be or what else I should check?

    It's worth noting there's no misfires or anything of that sort. The engine feels smooth, just slow, as if I'm barely on the throttle at all.

  2. #2
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    What was the vanos code? Sounds like your seal(s) could be bad in it. The piston could be hanging up in there. High rpms helps it along.

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    Quote Originally Posted by WBAD530i View Post
    What was the vanos code? Sounds like your seal(s) could be bad in it. The piston could be hanging up in there. High rpms helps it along.
    I actually don't recall, I think it was something was getting stuck so that might be it. Is doing the VANOS seal a big job?

    It seems to have power again once I hit the high RPMs but it takes a while to get up there. Today I tried full kickdown from a standing start and had absolutely nothing then suddenly sprang to life and took off like a rocket, but later on it went back to slow again all the way to 100. It's very strange since I'd gone two weeks without a single problem.
    Last edited by CarterH; 02-16-2019 at 12:26 AM.

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    Your description lines up with the symptoms. Also check the DISA valve as it can do similar things. Rebuild that with one of the aluminum flap/screw kits and never worry about it again unless the diaphragm breaks in it.

    The vanos job is very easy and well documented if you look around. If you are just getting into DIY jobs on the e39 this is an excellent start. Also get something you can read codes with yourself. A simple cheap reader that displays the P code and brief description would suffice. Having one of these in the car at all times is ideal.
    Last edited by WBAD530i; 02-16-2019 at 01:10 AM.

  5. #5
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    Quote Originally Posted by WBAD530i View Post
    Your description lines up with the symptoms. Also check the DISA valve as it can do similar things. Rebuild that with one of the aluminum flap/screw kits and never worry about it again unless the diaphragm breaks in it.

    The vanos job is very easy and well documented if you look around. If you are just getting into DIY jobs on the e39 this is an excellent start. Also get something you can read codes with yourself. A simple cheap reader that displays the P code and brief description would suffice. Having one of these in the car at all times is ideal.
    I'll take a look at some kits, I recall the valve gasket needs to be done when doing this so at least that'll be another item off the list. I'd heard the VANOS job can be a few hours minimum but it'll be nice if it's nothing too massive and doesn't take that long.

    I was going to get PA Soft but I'm wondering if I really need it since I won't be doing much coding and only planned on having it for fixing my cluster. Are there any good code readers I can get off eBay? One that can also reset the service lights would be great too since I have the brake fluid clock symbol currently.

    Oh and there's also no noise from the VANOS. Not rattling or marbles noise like some people report.
    Last edited by CarterH; 02-16-2019 at 01:56 AM.

  6. #6
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    What year E39?
    Check out Rajaie's site. He has the VANOS seal R&R procedures listed for both single & double VANOS:
    http://www.beisansystems.com/procedures/
    Ed CT
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  7. #7
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    geargrinder is offline Having No Trouble Here BMW CCA Member
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    Quote Originally Posted by WBAD530i View Post
    Your description lines up with the symptoms. Also check the DISA valve as it can do similar things. Rebuild that with one of the aluminum flap/screw kits and never worry about it again unless the diaphragm breaks in it.

    The vanos job is very easy and well documented if you look around. If you are just getting into DIY jobs on the e39 this is an excellent start. Also get something you can read codes with yourself. A simple cheap reader that displays the P code and brief description would suffice. Having one of these in the car at all times is ideal.
    I agreed 100%... sounds very much like VANOS but DISA could be a candidate too. Worth looking at anyway to be sure you're in good shape there.
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  8. #8
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    Quote Originally Posted by Ed CT View Post
    What year E39?
    Check out Rajaie's site. He has the VANOS seal R&R procedures listed for both single & double VANOS:
    http://www.beisansystems.com/procedures/
    I have a late 1997 build with single VANOS. I had a look at the guide and saw "P1519 (BMW 212, 0xD4): Vanos mechanically stuck (jamming)" which is indeed the codes description that I had cleared, so VANOS it is then. I'll have the codes read again today and see if it's returned. That guide looks great and tonnes of pictures it's just the way I like it.

    Quote Originally Posted by geargrinder View Post
    I agreed 100%... sounds very much like VANOS but DISA could be a candidate too. Worth looking at anyway to be sure you're in good shape there.
    I'll check that out too. It doesn't seem to be making any noise like in some videos I've seen but I'll take it off and see if it's opening and closing okay. I took the car for a drive last night and went along some walls with the windows down and did hear a slight watery burble noise on acceleration, I'm not sure if that's related in some way. My old E34 had a similar burble noise so it may just be normal? The only cars I've had for the last 5 years have been BMWs so I don't know much about other cars anymore

  9. #9
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    A few updates:
    I have no DISA valve, it seems early ones didn't.
    No codes have returned or appeared, the car has accumulated none over the last few weeks and there is no check engine light.
    I've been to an indie mechanic that has no idea what it could be and I had roadside assistance come on a bad day of sluggish driving and they said it might be the MAF and had no idea what else to say, since it didn't go sluggish when either of them were inspecting it.
    Using the transmission in steptronic doesn't seem to make much difference (if at all).

    I drove it on an ice cold night and it performed like a bullet, but then again maybe I just got lucky since it's intermittent? It mostly goes bad on hot days as far as I can tell. Either way, when it turns to a slug, it feels like I'm pulling an invisible weight with it. I find it strange that there's no codes, lights on or strange noises since others usually report that when it's VANOS.

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