Help!!! 645i Engine issue? Odd one!
Discussion
My father inlaw has a 54 plate 645i with 48k on the clock. Last week it threw up an emissions fault and was taken to his local indy straight away. After the weekend i phoned the indy to find out what codes had been pulled. This is the only code that showed itself:
27b8 - Differential pressure sensor, intake manifold, not plausible. Testing of the system was showed that there was a massive pressure error.
Some research suggested some simple possible fixes such as, MAF dirty, Inlet clogged with oil and dirt, Failed Sensor, Air Leak somewhere, Failed air pump, and finally a fulty alternator causing spurious ECU messages.
With some on-car investigation we found that two gaskets on the inlet manifold had split so we replaced them immediately. On turning the ignition the faults cleared and with a positive result we left the car to warm on tick over. Once the cold start ended there was a return of the error and the car was idling roughly. Oops!!
As far as i understand, during cold start and warm up the engine uses the throttle butterflies to adjust the fueling and air flow. Once the car reaches the required running temperature it switches from the throttle butterflies to the variable valve / valvetronic system. Its at this point that we are having our problem.
Testing the system and monitoring its processes it seems that the valvetronic system is running in reverse. Instead of opening the valves it appears to be locking them closed, creating massive overpressure and potentially damaging the internals. This overpressure is obviously the reason why the gaskets blown before. We've changed the ignition control module with a module we know is working with no success. We dont have a decoded ECU to try so as yet we cannot rule out the ECU as the culprit.
Does anyone have any suggestions? BMW have been asked and they cannot find a reason along with every other specialist and diagnostics guru we know. Short of stripping the engine down we cannot see anything else that could be at fault. Smoke tests shown no leaks and good pressure, but every time we run it up to temp it locks up and the car goes into limp mode.
One thing i will add is that a few weeks ago the IDrive froze for the day. He had a blank screen and had no radio, climate, nav or phone. Could it be an electrical issue or failed loom? I had a broken loom on my E61 M5 and it played havoc with all sorts, but i cant see the comfort wiring affecting the engine directly?? Heeeellllllppppppp!!
Eddie
27b8 - Differential pressure sensor, intake manifold, not plausible. Testing of the system was showed that there was a massive pressure error.
Some research suggested some simple possible fixes such as, MAF dirty, Inlet clogged with oil and dirt, Failed Sensor, Air Leak somewhere, Failed air pump, and finally a fulty alternator causing spurious ECU messages.
With some on-car investigation we found that two gaskets on the inlet manifold had split so we replaced them immediately. On turning the ignition the faults cleared and with a positive result we left the car to warm on tick over. Once the cold start ended there was a return of the error and the car was idling roughly. Oops!!
As far as i understand, during cold start and warm up the engine uses the throttle butterflies to adjust the fueling and air flow. Once the car reaches the required running temperature it switches from the throttle butterflies to the variable valve / valvetronic system. Its at this point that we are having our problem.
Testing the system and monitoring its processes it seems that the valvetronic system is running in reverse. Instead of opening the valves it appears to be locking them closed, creating massive overpressure and potentially damaging the internals. This overpressure is obviously the reason why the gaskets blown before. We've changed the ignition control module with a module we know is working with no success. We dont have a decoded ECU to try so as yet we cannot rule out the ECU as the culprit.
Does anyone have any suggestions? BMW have been asked and they cannot find a reason along with every other specialist and diagnostics guru we know. Short of stripping the engine down we cannot see anything else that could be at fault. Smoke tests shown no leaks and good pressure, but every time we run it up to temp it locks up and the car goes into limp mode.
One thing i will add is that a few weeks ago the IDrive froze for the day. He had a blank screen and had no radio, climate, nav or phone. Could it be an electrical issue or failed loom? I had a broken loom on my E61 M5 and it played havoc with all sorts, but i cant see the comfort wiring affecting the engine directly?? Heeeellllllppppppp!!
Eddie
Ok, we took the car to my favourite dealer, Scotthall Southampton this afternoon (they look after my E61 M5 fantasticly) following the Indy's reluctance to persue the issue any further. Not really thier fault, just seemed too big and unusual a problem for them to get heavily involved in (£344 bill for the work they did though). Anyway,
We sat down with the service rep and i explained everything we had tried and continued to push my belief that the valvetronic motor was out of sync due to the ECU possibly being a bit misguided or in need of a reflash. It turns out the Indy did not reflash the ECU as they didnt have the facility and did not want the responsibilty of the risks involved. As per normal with Scotthall they were more than happy to hear the theories of the punter and i left them an A4 sheet of scribbles to keep them occupied. It kind of makes sense when you break down the problems and symptoms, along with the fact that the IDrive plays up. Wiggly amps galore in these things and its always linked somehow.
We left feeling more confident (well i did anyway, the father in law cried) and awaited the call following the diagnostics pull. By 3.30pm we'd had a call from the rep and sure enough they could see that the ECU was in need of a reprogram ref the valvetronic motor and sensors. The reflash will take a few hours so they are going to leave it overnight to download the appropriate files. If its works then it'll be a low cost repair, heres hoping and fingers crossed for my father in law.
There's your update for the day, i'll post up tomorrow when i know more.
Eddie
p.s. Just a point of interest. The pressure in the inlet manifold should be around 45 to 55mbar. We were seeing over 530mbar which gives an indication of the problem.
We sat down with the service rep and i explained everything we had tried and continued to push my belief that the valvetronic motor was out of sync due to the ECU possibly being a bit misguided or in need of a reflash. It turns out the Indy did not reflash the ECU as they didnt have the facility and did not want the responsibilty of the risks involved. As per normal with Scotthall they were more than happy to hear the theories of the punter and i left them an A4 sheet of scribbles to keep them occupied. It kind of makes sense when you break down the problems and symptoms, along with the fact that the IDrive plays up. Wiggly amps galore in these things and its always linked somehow.
We left feeling more confident (well i did anyway, the father in law cried) and awaited the call following the diagnostics pull. By 3.30pm we'd had a call from the rep and sure enough they could see that the ECU was in need of a reprogram ref the valvetronic motor and sensors. The reflash will take a few hours so they are going to leave it overnight to download the appropriate files. If its works then it'll be a low cost repair, heres hoping and fingers crossed for my father in law.
There's your update for the day, i'll post up tomorrow when i know more.
Eddie
p.s. Just a point of interest. The pressure in the inlet manifold should be around 45 to 55mbar. We were seeing over 530mbar which gives an indication of the problem.
Ok, we've got the car back now and with a very positive result. As per my suggestion it looks like the ECU had got confused and was causing the Valvetronic Timing Motor to desynchronise, reversing /misguiding the timing to a point where the inlet manifiold was under immense pressure. The cars variable length manifold could only operate over a certain range as a result, but it could have been worse given the fact that it could have completely killed itself had the timing been completely out.
The solution was to do a complete reprogramming of the ECU and all other ancilliary modules. It took a whole night and day linked up to a laptop to do it but the result was as intended. On top of that the 2004 Idrive screen now shows the latest display and some of the other functions have been modified to a more recent spec. Engine and gearbox software now also have all of the latest tweaks. Apparently, according to the father in law you can actually feel the difference when going through the gears.
The father in law is very happy as you can imagine and the drive home was a pleasure. To top it off the cost was only £134 inc a full valet.
This is why i take my M5 there. Hots off to Scotthall yet again.
Eddie
The solution was to do a complete reprogramming of the ECU and all other ancilliary modules. It took a whole night and day linked up to a laptop to do it but the result was as intended. On top of that the 2004 Idrive screen now shows the latest display and some of the other functions have been modified to a more recent spec. Engine and gearbox software now also have all of the latest tweaks. Apparently, according to the father in law you can actually feel the difference when going through the gears.
The father in law is very happy as you can imagine and the drive home was a pleasure. To top it off the cost was only £134 inc a full valet.
This is why i take my M5 there. Hots off to Scotthall yet again.
Eddie
Thanks for updating us. Seems a weakness that the electronic systems can lose their mechanical reference somehow, i wonder if the reflashing is as much about updating the software to avoid this problem in the future as correcting the immediate mal-synch problem. Can't be the first time this has happened in the field, did you get the sense you weren't the first time they'd seen this.
I quite fancy one of those 645ci's as they approach 8k territory.
I quite fancy one of those 645ci's as they approach 8k territory.
I dont think its something they will have seen a lot of given the fact that there were not many 645s made. If they had then surely the Indy that was used first would have been able to shed more light. Had i not seen the US recall bulletin for the 745i (and later the 545i) i think the process would have lasted a little longer too. A full diagnostics pull would have found it for sure but my suggestion / theory did speed things up a little.
Other than that Joes 645 has been a bullet proof purchase, only requiring the Idrive to be replaced a couple of years back under warranty. £8k is a bargain for a car that cost him £50k in 2005.
Eddie
Other than that Joes 645 has been a bullet proof purchase, only requiring the Idrive to be replaced a couple of years back under warranty. £8k is a bargain for a car that cost him £50k in 2005.
Eddie
Indy garages are great for simple stuff and basic servicing, but for complex motors and fault finding, main dealers are often the best bet in my experiences. Whilst you may begruge paying for diagnositics, you often end up paying twice at indys and main dealers are usually more willing to look at issues again free of charge if they dont get it right first time.
Glad you got a positive outcome on the 645i anyway
Glad you got a positive outcome on the 645i anyway
Interesting. I had my car (2005 650) serviced last week by my BMW Specialist and asked if he would check the SW. He did and informed me that 23 of the modules had updates available, so it is in for a SW update.
I will report back on any improvements I notice.
The reason I wanted the latest SW is that on my 1999 740, I thought I was in for a big bill, as sometimes when accelerating hard down a slip road, the kick down was occasionally very abrupt. A quick SW update made it creamy smooth, difficult to believe it was the same car afterwards.
I will report back on any improvements I notice.
The reason I wanted the latest SW is that on my 1999 740, I thought I was in for a big bill, as sometimes when accelerating hard down a slip road, the kick down was occasionally very abrupt. A quick SW update made it creamy smooth, difficult to believe it was the same car afterwards.
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