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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 08-26-2013, 05:33 AM
sheppy sheppy is offline
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Mein Auto: e39 m52 528i
Persistent Hesitation Problems

I seem to have the BMW from hell and would appreciate any advice. It's a 1997 m52 automatic 528i and I've been experiencing extreme hesitation when accelerating under load for some time, although it can be an intermittent problem. At times when driving uphill, I have to manually select second gear and floor the accelerator to get it to move. There is hardly any power until the engine gets above about 5000rpm, then it will kick into life and surge forwards, at which point I can shift back to drive. Other symptoms are a rough idle at times, which occasionally wanders a little.

I initially suspected an air leak on the intake, or a faulty MAF sensor, so I replaced that along with the intake manifold gaskets, and checked all the hoses for leaks. This did not solve the problem.

Next step was a trip to the dealer to get the fault codes read. It showed a vanos mechanically jammed fault and a faulty oxygen sensor. I ordered new Teflon seals for the vanos, and two new oxygen sensors (genuine) and got the dealer to install them for me. This did not fix the problem either, and the same fault codes were present. The BMW dealer tried to run a test on the refurbished vanos, but they were unable to get the test to run, apparently due to its jammed condition. Because it was not new, they blamed the vanos still.

Next I ordered a completely refurbished vanos from Dr Vanos, and this time fitted it myself. The car still has the same hesitation and fault codes present. I'm just about out of ideas now, and am rapidly running out of cash too! Can anyone suggest anything that may be the culprit? The only thing I can think of is the engine management module itself.

Thanks for any advice.

Last edited by sheppy; 08-26-2013 at 05:35 AM.
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  #2  
Old 08-26-2013, 05:36 AM
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dtadrian dtadrian is offline
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Mein Auto: 1999 BMW 528i T Wagon
Persistent Hesitation Problems

Have you smoke tested?


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  #3  
Old 08-26-2013, 05:38 AM
Burning2nd Burning2nd is online now
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  #4  
Old 08-26-2013, 05:40 AM
sheppy sheppy is offline
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I asked the BMW dealer to check for air leaks after I replaced the intake manifold gaskets and hoses, but they found nothing. I assume they tested using a smoke test but can't be sure.

I also checked and cleaned the ICV, but it wasn't stuck.
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  #5  
Old 08-26-2013, 05:45 AM
sheppy sheppy is offline
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At the time I didn't have the tools to lock the timing in place, so got the dealer to do the job. It's not easy to find specialist tools in New Zealand, but I've since purchased them from the USA. I even had to visit four local auto stores before I managed to find a set of female torx drivers so that I could slacken the exhaust cam sprocket. Nearly all cars here are Japanese.
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  #6  
Old 08-26-2013, 08:17 AM
rdl rdl is offline
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Sheppy
Your car has an engine & transmission different from my 530, so my suggestions are general, not specific to your car.

Since new O2 sensors & VANOS didn't eliminate the codes, one does suspect either an ECU/DME fault or damaged wiring harnesses to those components or perhaps a bad VANOS solenoid (assuming the new VANOS didn't include that)
What are the all the DTC Pxxxx codes being found? Which are active/current vs old vs pending?

Does your engine have the DISA in the inlet manifold? If yes, I'd confirm that it is intact and functioning correctly. It's supposed to switch at ~3,800 RPM which isn't quite the same as the 5,000 you describe, but perhaps might be involved. See the Best Links thread for info.

You mention sluggish on a hill. Is it also sluggish pulling away from a stop?
Because I'm also suspicious of the transmission since it doesn't downshift on it's own when you are losing speed while climbing a hill. Every automatic I've ever driven would downshift at some point as I depress the throttle to maintain speed on a steepish hill. I don't mean to max RPM passing gear, but a downshift of one gear, say from 5th to 4th, then if necessary again from 4th to 3rd on a very steep hill - just enough to maintain speed. I've never had to manually force a shift to a lower gear to maintain speed on a hill.

So perhaps a silly question, but did the scan for DTCs include the transmisson?
Will the transmission downshift to passing gear on its own if you floor the gas pedal past the kickdown detent?

Last, intermittent problems can be a real challenge to say the least. It might be worthwhile taking the diagnostic system for a drive while monitoring key engine and transmission data, i.e. try to catch the problem "red-handed." In the interest of safety, two people: one to drive & one to monitor.
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  #7  
Old 08-26-2013, 08:22 AM
mda185 mda185 is offline
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Two things come to mind. Have you or the dealer inspected the crankcase ventilation system parts? Otherwise known as CCV. On your engine, I believe it is just an air/oil separator buried under the intake manifold with a drain going to the dipstick tube and another line going to the intake manifold or intake boot. Any leak here is a vacuum leak and can cause the symptoms you describe. If yours is old, just replace it proactively. Leaks in this system cause massive hesitation on my 530i. The other thing that can cause this but is not very common is a crack in the plastic valve cover. This is also a vacuum leak. I am not even sure if a smoke test will find a cracked valve cover. Leaking valve cover gasket would also potentially cause hesitation.
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Old 08-26-2013, 09:01 AM
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mjalloul11 mjalloul11 is online now
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What about your spark plugs? Have you check them? Also there is a small air valve on a tip of an air hose next to the purge valve and intake manifold which you press to open. mine was jammed open with the same results, a vacume leak.
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  #9  
Old 08-26-2013, 02:14 PM
sheppy sheppy is offline
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Thanks for all the suggestions so far. My car does not have a DISA fitted, and I didn't really consider the CCV as a possibility as it was replaced about two years ago. I did check the mounting rubber and the hoses for leaks on it when I replaced the manifold gaskets, and they all seemed ok. Also there is a slight inward pressure when you remove the oil filler cap with the engine running, and no appreciable pressure at the dip stick tube. I suppose it is still a possibility though.

The spark plugs are brand new - I changed these recently and experienced no change in behaviour. Not sure about the air valve near the intake manifold, but I'll take a look and see if I can locate it thanks.

Regarding the transmission, there may well be an additional problem here as it doesn't automatically downshift when the hesitation occurs and the car loses speed. However, when I manually switch to 2nd gear, the hesitation still occurs until the engine finally makes it above about 5000rpm. Also there is a rough idle when the car is misbehaving, and it does hesitate from a standstill as well sometimes. I haven't had the transmission codes read, but it may well be worth doing so. But I'm inclined to think this isn't the main problem.

I don't believe there is a leak on the valve cover. I had to remove it to replace the vanos, and noticed no cracks. I replaced all the gaskets and mounting bolt rubbers when I reassembled.

The only two current fault codes registered were the faulty oxygen sensor, and jammed vanos ones. Not sure of the historic ones as the dealer cleared them before giving the car a short drive and retesting.

Thanks again for all the help so far.
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  #10  
Old 08-26-2013, 02:37 PM
mda185 mda185 is offline
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The only other fault that is vacuum related that I can think of is a leaking diaphragm in the power brake booster. That also will cause driveability problems and hesitation. It does not happen often but probably should be checked out. Easiest way i can think of to test this theory is to disconnect vacuum line going to booster and plug it. Try a short drive somewhere safe without traffic and pedestrians around because you will not have power assist on your brakes. If hesitation stops, you know what to replace. If it doesn't I don't know what else to suggest.
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  #11  
Old 08-26-2013, 04:48 PM
sheppy sheppy is offline
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Thanks Mda185, I'll check the brake booster today. I'm pretty much out of ideas as well, unless the ECU is faulty, though I would have thought the dealer's diagnostics would have revealed that when they read the fault codes, unless it's an unusual failure that causes the ECU to output faulty data that is within a plausible range.
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  #12  
Old 08-26-2013, 05:25 PM
pshovest pshovest is offline
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How many miles?
Did you replace the rubber boot between MAF and throttle body?
Does it run better w/MAF disconnected?
Can you check fuel pressure at the rail?
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  #13  
Old 08-26-2013, 05:47 PM
poolman poolman is online now
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You kept getting codes that said the Vanos was jammed--is there power getting to the Vanos solinoid? sounds like you have already taken care of vacuum leaks--
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  #14  
Old 08-26-2013, 06:51 PM
sheppy sheppy is offline
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The BMW dealer said that they had checked the cables leading to the solenoid, and the connection was fine. The solenoid has been tested and activates correctly, and has the correct resistance (again according to the dealer).

I inspected the MAF-throttle boot and it was fine, so didn't replace it. I did replace the throttle body-manifold gasket. I've sprayed the entire inlet area with brake cleaner and noticed no engine surges, so I'm fairly confident that there are no inlet leaks.

The car does run better with the MAF disconnected, but I've already replaced the MAF and it made no difference to the running of the car once reconnected - even after hundreds of miles of driving. As I understand it, disconnecting the MAF causes a whole lot of other feedback systems to be disconnected as well, so is not a reliable test of the MAF condition. Is that an incorrect assumption? It's something I read somewhere previously.

The car has done about 130,000km (80,000 miles). Fuel pressure was checked by the dealer, which they said was good. There are no error codes stored that might indicate ignition coil problems either.
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  #15  
Old 08-26-2013, 07:12 PM
pshovest pshovest is offline
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Disconnecting MAF is not a reliable test of the MAF. But cars with new MAF's that run better w/ MAF disconnected often are ingesting air that didn't pass thru MAF. This air is enterring thru leaky/cracked intake boots, CVV hoses, etc. Air that the MAF doesn't know about results in lean conditions. If you inspected intake boot by removing completely, then look closely at CVV hoses. If you didn't remove intake boot, do so and check for cracks between corrugations. Also check boot at ICV. Lean conditions can cause O2 sensor codes.

Quote:
Originally Posted by sheppy View Post
..........The car does run better with the MAF disconnected, but I've already replaced the MAF and it made no difference to the running of the car once reconnected - even after hundreds of miles of driving. As I understand it, disconnecting the MAF causes a whole lot of other feedback systems to be disconnected as well, so is not a reliable test of the MAF condition. Is that an incorrect assumption? It's something I read somewhere previously.............

Last edited by pshovest; 08-26-2013 at 07:13 PM. Reason: typo
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  #16  
Old 08-26-2013, 07:22 PM
sheppy sheppy is offline
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Good to know, thanks. I did completely disconnect the CCV, ICV and throttle body (hence the intake boot as well) when I replaced the manifold gaskets. I'm confident that the seals and hoses are ok. But maybe as a precaution I should replace the CCV and ICV mounting rubber seals, perhaps even the CCV itself, even though it's only about two years old.

Quote:
Originally Posted by pshovest View Post
Disconnecting MAF is not a reliable test of the MAF. But cars with new MAF's that run better w/ MAF disconnected often are ingesting air that didn't pass thru MAF. This air is enterring thru leaky/cracked intake boots, CVV hoses, etc. Air that the MAF doesn't know about results in lean conditions. If you inspected intake boot by removing completely, then look closely at CVV hoses. If you didn't remove intake boot, do so and check for cracks between corrugations. Also check boot at ICV. Lean conditions can cause O2 sensor codes.
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  #17  
Old 08-29-2013, 08:17 PM
sheppy sheppy is offline
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Smile

Thanks for all the received suggestions. It turns out that the new vanos from Dr Vanos did clear up the error code, but only after a few days. Perhaps the new seals were sticking for a while until they bedded in.

The O2 sensor issues were caused by a missing gasket on the throttle housing, which I replaced last year, but has mysteriously disappeared since then. I suspect the garage might have forgotten to reinstall it when I asked them to check for air leaks some time ago, but I have no proof.

Anyway, the main thing is that it's running well now for the first time in months! Thanks again for all the responses.
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  #18  
Old 08-29-2013, 09:05 PM
AH673000 AH673000 is offline
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Mein Auto: 1997 BMW 528i
Persistent Hesitation Problems

Thanks for sharing.... Great job of sticking with it..... Your OBD2 codes certainly had you pointed toward the correct faults which is good to know .


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