I have a 2007 750i with 83K miles. when I got it, it was running rough and gave me a code that a couple of cylinders were misfiring. I repalced all the spark plugs and coils. I then got cylinder 5 misfire. I put some cleaner in the tank, ran a full tank to clean carbon. still had cylinder 5 misfire. I swapped the injectors between 5 and 6, got cylinder 6 misfire. I replaced the injector, car ran a lot better but latter gave me cylinder 5 misfire again. I unplugged the eccentric shaft sensor(driver side), left it off, engine runs perfect. Plug back sensor, reset and recalibrate, car runs great. One day later car is running rough again(better than at first) with cylinder 5 misfire again. What could br the issue? is it the sensor?
Note: When i got the car, I noticed that the passenger side eccentric shat sensor was compltetely missing the gasket/washer and had a vaccuum leak there. I since then put on the gasket. I wonder why that gasket was missing and if the previous owner had work done on the sensor. could this have something to do with it? Any help would be greatly appreciated.
Thanks in advance:tsk::tsk::tsk:
I checked CCV, no tears. Had a vacuum leak before, replaced missing gasket took care of that. Did smoke test no leak. Did block test(blow by), not head gasket issue. Runs good when eccentric valve is unplugged. Valvetronic set at 0.8 mm valve lift. Don't have the right software. I work for a Lexus dealer. Don't know what else to do.
Tough to diagnose these complex engines without the BMW software ....
When you disconnect the eccentric shaft sensor, it defaults to maximum valve lift, 9.7mm (and obviously Valvetronic is NOT active), and the throttle body is used for the air/throttle management.
You've already checked everything that would cause a misfire on a single cylinder like injector, coil and plugs. Any other thing associated with ignition, timing etc is common to all the other cylinders and would not explain a misfire on a single cylinder.
The only thing left to do is a compression test on that cylinder... There is a good chance at this point that's what the problem is.
I guess that would do it if air is only coming in at that point into cylinder 5 only. Is that bank running slightly lean? I guess if the other cylinders are fine then it might be difficult for the catalytic converter to pick up anything in the exhaust.
ralph, for my curiosity, how did you discover the small leak in the VCG ? Was there a visible chunk or rubber gasket missing ? Why didn't (or wouldn't) the smoke test have seen this void ?
Turns out the leak was from the gasket from the injector not sitting properly. Not the gaskets. Car is running a lot better, still some hesitation present at high torque demand. We found some rust at the connection of the DME and and small wire harness. I'm now being told that the DME needs to be replaced. Not sending signal to cylinder 5. What do you guys think?:dunno:
unplug both eccentric shaft sensors and drive it. This will put the valvetronic in failsafe giving you maxium valve lift. If the misfire goes away the problem is in the intermediate-accentric shaft-rocker arm assy
"The ECM has eight Final Stage output transistors that switch ground to the eight injector solenoids. The Injector "triggering" is first established from the Crankshaft Position/RPM Sensor.
The ECM is programmed to activate the Final Stage output transistors once (per cylinder) for every working cycle of the engine (Full Sequential Injection). The ECM calculates the total milli-second time to open the injectors and triggers them independently."
"The ECM has eight Final Stage output transistors that switch ground to the eight injector solenoids. The Injector "triggering" is first established from the Crankshaft Position/RPM Sensor.
The ECM is programmed to activate the Final Stage output transistors once (per cylinder) for every working cycle of the engine (Full Sequential Injection). The ECM calculates the total milli-second time to open the injectors and triggers them independently."
supposedly, the transistor for cylinder 5 is bad. It appears due to water damage. We found rust where the wire connects to it. When I first start the car, it runs fine. Shortly after, 5 min or so, it stars hesitating. If I shut the car off, it resets and runs fine for a while. Does that sound like the DME?
I found out that is not the valve. Still trying to find out what's going on. So far we've ruled out: the valves, coils, plugs; changed the valvetronic sensor, swapped the motors from each side; even swapped the control module, still doing it. No solution so far.
hey i am having the same problem with my 7. we have not found the problem and it have been in the shop for a month. it all started with me changing the knock sensor, spark plugs and coils. have anybody found a solution to why these cars misfire????? S.O.S
i have measured pressure of oil, it jumped. (1,5 bar to 3 bar). Next, i have dismont engine, i've noticed, that it is coverd up on pans... drama....I must change engine to new-used.. No it's ok At last...
I just got my 7 back from the shop because of misfiring on cyinder 5 after I changed the spark plugs and coils. It turn out to be the MAF and number 1 fuel sensing unit telling the car it was empty. We changed them both and the car is running and responsing nice
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
BimmerFest BMW Forum
11.4M posts
754.1K members
Since 2001
A forum community dedicated to BMW owners and enthusiasts. Come join the discussion about Bimmerfest events, production numbers, programming, performance, modifications, classifieds, troubleshooting, maintenance, and more! Bringing the BMW community together.