Problematic behaviour
I’m having problems with a 2007 BMW 325i M-line with 80,000 miles. The car was bought a few years ago in excellent condition, but has been problematic since then.
When starting from cold in the morning, and also when the engine is warm after 100 miles or so, it starts driving very roughly, as if it’s not running on all cylinders or the mixture is very rich or poor. When this happens in the morning after starting, the EOBD light illuminates and you can’t drive faster than 30-35mph. The trick I developed is to stop the engine and restart it. In 80% of cases it then drives fine, but in the other 20% the EOBD light still illuminates and the engine does not run as it should, although power is restored.
When the engine is warm after a long run and you stop, say for a traffic light, the EOBD light turns on within 15 seconds. The engine runs roughly, but not as badly as when it’s cold. The rev counter dances on the scale, but when you continue driving, all is normal again. Sometimes the EOBD light remains lit for three days at a stretch, but the car runs fine.
The problem may not manifest itself for two to three weeks, petrol consumption seems normal and it’s using half-a-litre of oil every 1300 miles. I’ve also noticed that the exhaust pipe is very black. On the motorway, when I overtake another car and have to make power, there is a lot black smoke from the exhaust.
I had the car diagnosed locally and found that the injectors on cylinders 1 and 2 were not working properly. All six were sent to an outside firm for cleaning, but when the problem returned, the injectors on cylinders 5 and 6 were to blame. Six new injectors were fitted, but it has made no difference. I also replaced the fuel pressure sensor and all of the coils and plugs. In spite of the new injectors, the diagnostics reader still says the injectors for cylinders 5 and 6 are not good, but replacing them with the good ones from cylinders 1 and 2 makes no difference. The car was then sent for three days to a German Bmw-dealer/garage to be repaired there. They said that the injectors on cylinders 1 and 2 – which were new – were at fault, not 5 and 6!
I have established that other people with same car/engine have the same problem. Do you think there is a solution? Rolf Knijff My first comment is that the injectors should be coded to the cylinder – hopefully, this should have been done by the dealer, but will have been upset by swapping the injectors around. The coding data is printed as a six-digit number on the injector body.
however, be related to the ABS pump/ module unit or one of the other sensors in the system. For this reason, the only way to narrow down the problem is to list any fault codes in the system. If no
I am also assuming that the dealer checked the fuel pressure regulator and that this is correct for the vehicle. This is very important with the injection system on your BMW and official literature says, with regards to such problems, to always to confirm the fuel pressure. This is a check that the dealer should have carried out to ensure the fuel line pressure is sufficient. It should always be maintained at a higher pressure than the regulator is set. Also, If you have not already done so, I would replace the fuel filter.
When the injectors fail they over-fuel. The ECU then detects the rich mixture from the reading given by the 02 sensor. As the 02 sensor does not specify which cylinder is over-fuelling, only which bank, the fuel to all three injectors in the bank is reduced. The result of this is that the two good injectors are not putting sufficient fuel into the cylinder. This fault codes are present, Autodata advises you to “Re-program ABS/ESP control module with upgraded software. To carry out an effective repair a software upgrade will be required – refer to manufacturer.” can result in a misfire detected in the two cylinders with good injectors. The simplest test to discover which cylinder is over-fuelling is to remove the spark plugs. The over-fuelling cylinder will have a black, sooty spark plug.
The injectors in the direct injection system are prone to carbon buildup. As you have had all six injectors replaced, as well as the plugs and coil packs, I would check the continuity and integrity of the injector plugs and loom, as well as the coil pack plugs and loom. Another point to ponder is the fuel quality – you should certainly consider only using a premium fuel, if possible.