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Help with misfire on cylinder 5

20K views 37 replies 9 participants last post by  N2Motion 
#1 ·
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:
 
#2 ·
Do you have a complete dump of error codes ?

You should likely be getting other error codes .. possible related to the sensors.

Did you check the 2 bank2 Camshaft sensors next to the eccentric shaft sensor ?
 
#6 ·
There is a DIY on misfires
http://www.bimmerfest.com/forums/showthread.php?t=432390

You've done some of the ignition/fuel related ones. Did you check the other common vacuum related items ? CCV or any other unmetered air issues ?

What software are you using ? INPA or DIS ? Check your Analog 1-3 readings (INPA) ..... Upstream O2 sensor readings, Fuel adaptations, MAF #,...
 
#7 ·
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.

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#12 ·
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.

Here are some good links .. .check the last link in past #1 titled Engine Diagnosis:
http://www.bimmerfest.com/forums/showthread.php?t=709673&highlight=diagnosis

Still could be related to intake ... MAF sensor ..
Or fuel pressure ...
Try swapping the camshaft sensors to bank1..

But doesn't explain why only #5 is misfiring ...
 
#13 ·
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.
 
#16 ·
I think we may have found the problem. Small leak in the valve cover gasket near cylinder 5. Going to replace gasket (both side) and see what happens.

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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.
 
#20 ·
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:
 
#21 ·
It is strange that you didn't get a code regarding the injector in the beginning !


My 2008 750LI has rough idle too with these codes :

P0305
P0204

One of the codes means cylinder #5 misfire.

The other code means Cylinder #6 injector circuit problem " probably the injector" .


I bought a new coil & injector before even starting the repair .


Will give you a feedback once finished
 
#24 ·
ralph, is the DME fault new ?

From the attached training manual (pg. 32) :

"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."

View attachment 02_Part 1 ME 9-2 DME.pdf
 
#25 ·
ralph, is the DME fault new ?

From the attached training manual (pg. 32) :

"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."

View attachment 403957
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?
 
#29 ·
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.
 
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