1997 E39 523i - Extreme power loss - Page 2

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  1.  
    #11
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    318is-joe's Car Details
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    Agree that it could be a blocked CAT - however the rotten egg sulphurous smell does not mean it is Knackered in it's own right - brand new cars often have this smell from the CAT and it is normal enough at certain temperatures.

    a very basic and simple test for a blocked pipe is - yes you guessed it - hold your hand or piece of paper at the tailpipe, and have a friend blip the throttle - there should be a noticeable surge of gas with the rev - if it remains constant - it is likely blocked and is choking the engine.

    The reason I didn't think it was a CAT problem was that the _carouser stated - the engine does rev out, but that it felt like it was not getting to the wheels.

    Blocked CAT's usually do not allow the engine rev freely - usually they struggle to get over 3,500 / 4,000 revs.
    That's my story and I'm sticking to it
     
     

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  3.  
    #12
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    the_carouser's Car Details
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    Would a blocked exhaust cause the engine to contain heat? I have had overheating problems and am on my 3rd radiator in the year and a half of owning the car. New radiator, hoses, thermostat housing (Metal). The other day, after driving and allowing the car to cool down for over 2 hours in cool evening weather, the radiator hoses were still rock hard with a build up of pressure. Not sure if this is normal.

    The other thing is shouldn't a knackered cat show an error code from both pre-cat and post-cat O2 sensors?
     
     

  4.  
    #13
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    318is-joe's Car Details
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    Quote Originally Posted by the_carouser View Post
    Would a blocked exhaust cause the engine to contain heat? I have had overheating problems and am on my 3rd radiator in the year and a half of owning the car. New radiator, hoses, thermostat housing (Metal). The other day, after driving and allowing the car to cool down for over 2 hours in cool evening weather, the radiator hoses were still rock hard with a build up of pressure. Not sure if this is normal.

    The other thing is shouldn't a knackered cat show an error code from both pre-cat and post-cat O2 sensors?
    OK - might cause the engine to run hotter (dunno in Australia I'm sure the ambient temp is a lot hotter to our climate) - but not over pressurise the cooling system. Sounds like there are a few smaller problems also. I would try replacing the expansion bottle (Coolant) cap if you think it is over pressurising - you shouldn't be going through radiators at that rate, and your mechanics should have tried changing the coolant cap.

    Yeah - pre and post O2 going off the scale or showing imbalance from poor flow should give up a code - my guess is that the CAT is not the problem.
     
     

  5.  
    #14
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    the_carouser's Car Details
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    Car is at the Indie at the moment. The diagnostic machine showed everything was in order with no error codes. Hard revving the engine in neutral exposed the burbling engine at high revs. Not something I did myself as all I knew the car started fine and idled fine, just drove like S*&t. The mechanic's first synopsis was that it seemed like I put diesel in the tank. I assured him I only use premium unleaded and no way that could happen. They still can't find the immediate problem. They suspect it's the MAF, and have taken it to test the calibration so they can rule it out. As far as the engine is concerned, all the electrics and mechanics are fine.

    I inquired about the transmission, but they say it is not the main problem. Once they get the engine running properly they will diagnose the transmission as a poor running engine could cause transmission faults. They thought it best to methodically deal with what is at hand than change every part to no avail (oh bless...looking after my interests & wallet?)

    I mentioned the exhaust blockage as an aside in the event the MAF checks out OK. He didn't rule it out as a possibility. They were out of ideas anyway. Meanwhile they gave me an '84 318i courtesy car to get around. After my car of late, it is a zippy little beast


    Should know more tomorrow.
     
     

  6. e39 1999 auto 2.8i TU engine 
    #15
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    patrickpears's Car Details
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    Hi

    I couldn't help not responding to your message.

    Does anyone know for sure if when you change the MAF if you have to have BMW diagnostics to clear fault codes before it will run ok ? I had a similar problem 2 or 3 years ago and a vac hose had gone and mechanic never cleared off fault codes, it then ran ok but mpg still poor, I insisted he did clear them and the mpg improved immediately so wonder if one has to do same for MAf.

    I have the above car and have had similar problems with 2 speciaists look at it . CCV valve, and some vac hoses changed, plugs, most injection parts cleaned such as Idle valve and Throttle Body.

    Mine has same problems, Even drove it without MAF connected, it was consistantly poor on power whereas normally it is poor low power and engine at all times is coarse almost like running on 4 or 5 cylinders.

    I then cleaned the MAF 3 times with non lubed Contact cleaner from Maplins, it did improve it a lot, thought best to also disconnect battery and leave for a period of say half to 1 hour to hopefully lose settings it has run on previously which did help.

    I was finding that when I slowed down in traffic I smelt the bad eggs and it wasn't me but the car.
    I had decided to replace MAF after mastercard state date and the previous weekend I took MAF off to give it a clean once more as nearly right. In putting it back my neighbors kids ran out from the side of the car startling me and I broke screen of maf which damaged the filament so had to change it.

    It doesn't seem to have made much difference and now hesitates a bit at low revs but does once on the cam fly - albeit coarsely. The engine ticks over as smooth as silk but coarse once you start to pull or put load on.

    If you put your foot down , it hesitates a second and then goes, I would have thought if it was an inlet manifold leak or vac leak it would have been lumpy.

    Perhaps you should try disconnecting the battery for a little while and re-conn then.
    However don't close boot or wherever battery is ( mine is an estate as you cannot open the boot then and have to climb over seats.
    you may get locked out.
    I am still trying to resolve my issue and believe that perhaps it is a cam sensor or lambda but have had no faults show up.

    I want o check out the first question I raised re clearing fault codes after new MAF fitted first.

    hope this helps
    Pat
     
     

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    #16
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    Latest Update. It was a blocked Catalytic Converter. I can't report any more as they had to order it in from interstate and didn't arrive till late today. It was a recommended after market unit that still cost me $1,010 just for the CAT. Double for the OEM version.
    Tomorrow is the weekend so not sure when I can finally talk to the mechanic about it and see how it drives.

    I did some research on dead CATs and was said it is not enough to just replace the CAT without finding out the cause of what may have killed it. I don't understand how any problems did not show up on the diagnostic machine if indeed the CAT was not performing. If the faulty CAT changed the fuel air mix, then wouldn't the O2 sensors be part of the equation and report that the levels measured wound not be acceptable and report a fault. I have never had a fault light come on in my dashboard for any problems I have had with the car. Correction, there is one fault light permanently on- that dreaded occupancy mat sensor fault light. Amazing, that the thing that is a waste of space and an unnecessary expensive repair (IMO) is the only thing that would always be in my face.

    Hope to have further news soon. Please let me know if anyone has any experiences regarding dead CAT causes that I need to get checked out.

    Cheers
     
     

  8.  
    #17
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    The Beast is Back!!!!

    Drove to and from work today and I had incredible power in the stop start traffic. I've had this issue so long that I forgot what the car used to be like. Thank you everyone for your input in resolving the problem. Three separate garages had the opportunity to drive and find the fault, but with no error codes on their fancy code reading machines, they failed to diagnose the problem. I followed Disco!!!'s lead to get them to look at the exhaust system which lead them to finding the problem. I don't know if mechanics knew the problem, but use the excuse of having to change everything else before they fix the actual problem.

    I am still a bit worried about the transmission even though I was given a clean bill of health . Although it seems fine, and haven't any of the slipping type issues that I was experiencing earlier (or thought I was), I did have it stuck in a single gear accelerating from standstill when I went out for lunch today. It was maybe 2nd or 3rd gear and used the steptronic to gear up. Eased everything down and all was fine again. Hasn't played up in the 1hr drive home....stop and start...but much faster...

    I am getting the transmission serviced soon from a dedicated transmission mechanic. I explained the problems that I had with CAT and how it was affecting the transmission. The transmission mechanic said that it was a common problem with blocked cats that give the impression that the gears are slipping. The car has 187,000 km on the clock and as far I know never been serviced. From what I've read, it is better to get it serviced before fatal problems arise, otherwise it could dislodge all the gunk that held it together stopping it from totally collapsing.

    Thank you again for all the suggestions and thoughts in diagnosing my problems. This is my first post and it is great to have a resolution, although still expensive, but could have cost me heaps more otherwise.
     
     

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    #18
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    Don't run the car low on fuel, that can block a cat.
     
     

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    #19
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    How does low fuel affect a cat?
     
     

  11. Bmw e39 523se 1998 sudden power loss 
    #20
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    0llie's Car Details
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    Hi i have a BMW e39 523SE (2.5) 1998

    I got the car and it had an over heating problem so once i had bleed the system and got all the air locks out all fixed YEY!!!

    Then the other day i was enjoying a ride around town for around 30mins and the temp gauge was sitting in the middle all fine. then suddenly LOSS OF POWER the engine starts to stutter and i cant run over 2000RPM, so i pull over engine stalls, start it up straight away again problem GONE.

    Now this has happened 3 times in this weekend, and the revs on idle sit very low around 450-500rpm with car rocking with the engine feeling like it struggling, and generally running rough.

    But the confusing part is on the motorway its drives fine getting around 35-50MPG lovely and smoothly. i have driven 1 hour 30 min in one go with no problem.

    update i was driving the car today on the motorway with the cruise control on the suddenly heard a click and then, no power, car starts slowing down, and i cant speed up. so i pull over on the hard shoulder, the engine is still running but around 250rpm. i switch it off, start up again a second later -- all fine im able to get to 70 in a matter of seconds.

    overall i feel like the car as lost some power it feels more sluggish.

    any ideas on my problem would be most appreciated thanks guys.
     
     

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