Hello All,

Long time lurker, infrequent poster!

So, I am totally stumped on this one and I am seeking help from the ‘Hive!’

As the title suggests, I have a 2007 750Li that has been relatively good to me for years. The issue started when the step daughter called and said the ‘car is smoking out the tail pipe’. I told her to pull over and shut the car off and I would be there shortly. I grabbed some oil and some coolant and headed on over expecting to see the car puking some sort of vital fluid. To my surprise nothing. I checked the dipstick and she was down about half a quart but she had been burning oil for quite sometime as she had 190,000 miles on the odometer. Checked the coolant tank and it was fine too. So I jumped in the car and headed home with the chase car following just in case it gave up the ghost.

We made it home and yes it was smoking (more so at slow speeds and less at faster speeds). Check the forums and came to the conclusion it was the CCV diaphragms so I popped them off and pulled them and sure enough both were ripped about half way around. Yay, easy fix (or so I thought). Replaced both diaphragms and no more smoke out the tail pipe but the idle was waaaaaaaay off. She used to be rock smooth at 550 rpm when I used to drive her (about 6 months ago) and the step daughter never complained about the idle so I suspect it had something to do with diaphragm replacement (perhaps). The idle now hunts only in Park and Neutral (500 rpm to 750 rpm, up and down, rhythmically). If I just leave it for a while, like 10 minutes it will make its way up to 1,500 rpm. Put it in Reverse or Drive and it drops down to 550rpm. I put the NT510 code reader on and it was throwing a MAF sensor error. I pulled the MAF and the idle seems to calm down a bit. Well there you go. I will just replace the MAF and she will be as good as new (unfortunately not). I put the new Bosche MAF on and no change. Now I start to get worried.

Ok, must be a vacuum leak right? Unmetered air getting in and throwing things out of balance? I do the smoke test several times and nothing is getting sucked in anywhere (front, back, sides and bottom of engine). Hmmm. So I think maybe the Idle Control Valve, seems logical, except the car does not have one. The idle is controlled by the Valvetronic system. So, I pull the Valvetronic actuators (yes I drilled the hole out on the top and unwound them), then tested them on the bench and they both spin in both directions. Ok, maybe itÂ’s the eccentric cam position sensor on one of the banks. Pull the connector to each one and see if it throws a code and yes it does. Plug it back in, clear the code and and re check-no code thrown. So I donÂ’t think it is either of those.

How about Cam Position Sensor? I pull the electrical connector on bank 5-8 (intake) and she starts but just barely. Plug it back in and starts just fine but idles like it is starving for something.

How about spark? Ok, changed all 8 spark plugs with Iridium ones still no difference.

Thought about maybe a head gasket as she was consuming coolant, but after replacing the CCV not a hint of white smoke comes out the tail pipe.

Electrical? Pulled the IVM (Intermediate Voltage Module) and tested all fuses and they were fine also sprayed it down with electrical cleaner just in case! No change same issue.

Any speed above 25 mph and you would not know a thing. Pull up to a stop and you get a slight hesitation but no real stumble. Pull away and she is certainly underpowered until you get north of 25 mph and then all is right with the world.

Any further places I should look? I also pulled the VANOS (Intake and Exhaust) on bank 5-8 and cleaned them, just in case.

Some last odds and ends. The NT510 is a pretty basic scanner but it does show the Adjust Angle (cylinders 5-8) at 0 degrees and the Adjustment Angle (cylinders 1-4) at 1.4 degrees. This discrepancy led me to believe it was the eccentric cam position sensor on cylinders 5-8.

This one has me baffled and any guidance would be appreciated.