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Discussion Starter #1
Ok... here's the story (see the TL;DR at the end if you don't like reading):

A couple months ago, I noticed that my M6 (167k miles) was very gradually sipping oil, as well as idling a tad rough. I read the PCV valve was the likely culprit. Fast forward to a couple days ago. I replaced the PCV valve and hose (kept the old o-ring). The old PCV hose had totally imploded; there's no way it was doing anything. But, that's fixed now, and the card idled smoother than I had ever seen it.

After fixing it, I got an oil change.

Later, I noticed that when I would accelerate (especially in the lower RPMs), the car would seem to stutter. Before replacing the PCV valve and hose, I had not noticed this. I read that the MAF sensor could need to be cleaned or replaced. So tonight, I disconnected the battery, unplugged the MAF sensor, and removed it. Upon examination, the temperature sensor looked a little dirty, but the airflow sensors seemed perfectly clean (as far as I could tell. I was trying to be very careful, so I didn't touch the sensor at all.) But I decided that I would clean the sensor even though it didn't appear to be dirty.

So, I decide that I'll drive to AutoZone to get some Mass Airflow Sensor cleaner. I put the sensor back in, plugged it in, and connected the battery. I go to start the car. It basically immediately stalls. I try several more times. No luck. I try again, revving the engine up right after I start it. Now, I'm able to get the car to idle appropriately. (Also, while doing this, it didn't seem that the engine was revving as high as it should be, given the amount of throttle I was giving it.)

Anyway, I shut the car off. I try to start it again (without giving it gas) and it stalls again. So I took the MAF sensor out to check for damage that I may have done (I was very careful when I took it out, but who knows). Didn't see anything. So I put it back in, and start the car.

This time, the car starts and appears to idle smoothly like it had been. I put some load on the engine (turn on AC, lights, etc). Now, the engine seemed to stutter like I mentioned a couple paragraphs back, but it seems much worse this time. (Previously, I had only noticed stutter during acceleration.)

I should note that there are no audible vaccum leaks. Also, when I had the intake manifold removed while replacing the PCV valve/hose, the hoses all looked remarkable, with the obvious exception of the PCV hose, which I replaced. (I'm wondering if the previous owner had the hoses replaced... they look very good for a 15 year old car.) My plan now is to buy a new sensor tomorrow morning and hope that fixes it.

Does anyone have any other ideas? Or, why would simply removing the sensor and putting it back cause it to go bad?

TL;DR - Car was slowly burning oil and had a bit of a rough idle. I replaced PCV valve and hose - problem solved. Now, the car stutters while accelerating. Removed MAF sensor to examine it, put it back in without doing anything to it. Car immediately stalls upon starting. Planning on replacing the MAF sensor tomorrow morning. Any other ideas?

Super Moderator
17,296 Posts
Sorry to hear about the problems.

Are you getting any codes or lights on the dash when it's starting up/stalling?

If you can find a MAF for a good price, I would start by replacing it, since it's the last/only thing that has changed in the car's environment that could be attributing to the stalls.
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