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  #11  
Old 11-23-2019, 09:58 AM
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And the DME is in the ebox - top, rear of engine bay on passenger side, correct? Where the IVM is?
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  #12  
Old 11-23-2019, 09:59 AM
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Quote:
Originally Posted by fishhouse4 View Post
I will check the connections on both ends.

The only two ideas my tech had was a new engine wiring harness (which would address those connections you just mentioned) OR a new DME. Both are stupid expensive...

Ok, help me here...this is what I don't get about the wiring/connection possibility:

It's just a wire, correct? It simply transmits the signal from point A (MAF) to point B (DME). Like... all or nothing, I would assume. So if the wiring or connections were damaged, then the signal wouldn't go to the DME. Which would be the exact same as having the MAF unplugged. So I would think in that case you would not get MAF signals to the DME regardless of if it was plugged in or not.

Or are you suggesting that the wiring/connections could be damaged in a way that could somehow degrade or corrupt the signal from the MAF??
The terminals can be dirty, corroded or even loose. Just visually inspect the terminal contacts and make sure they are not spread making a soft or poor contact on the MAF connector and on the DME connector. If you have an ohmmeter, check the continuity of the wires from one end to the other. It doesn't cost anything but a few minutes of your time to rule that out or validate an issue.
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  #13  
Old 11-23-2019, 10:03 AM
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Same on what brand MAF you are using...I ran into a similar problem with my e39 when I was trying autopart/eBay Maf's. Finally fixed when I purchased an "OE" MAF from Range Rover. (back when they had the m62's in them and were $200 bucks cheaper straight from dealer) I would still check connectors/terminals as you may have a working MAF that's not sending the correct readings.
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  #14  
Old 11-23-2019, 01:46 PM
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Quote:
Originally Posted by fishhouse4 View Post
I will check the connections on both ends.

The only two ideas my tech had was a new engine wiring harness (which would address those connections you just mentioned) OR a new DME. Both are stupid expensive...

Ok, help me here...this is what I don't get about the wiring/connection possibility:

It's just a wire, correct? It simply transmits the signal from point A (MAF) to point B (DME). Like... all or nothing, I would assume. So if the wiring or connections were damaged, then the signal wouldn't go to the DME. Which would be the exact same as having the MAF unplugged. So I would think in that case you would not get MAF signals to the DME regardless of if it was plugged in or not.

Or are you suggesting that the wiring/connections could be damaged in a way that could somehow degrade or corrupt the signal from the MAF??
First, I think the fact that 4 different MAFs all give the same result means they're all fine. More likely for that to be true than for all to be bad.

When the MAF is unplugged, the control system figures out how to manage things (engine and AT) based on what sensors and system model it has. Many different ways to do something like this, not sure on specifics. But the fact that it runs just fine with the MAF(s) unplugged suggests the rest of the car is good. Engine, even the ECU.

Just a thought, maybe when it switches out of MAF closed loop mode or whatever it is, it also switches out some other sensors (e.g., O2 sensors) while it runs open loop. If you can get good info on how the open and closed loop circuits work, that may be helpful in deciding where else to look for the root cause.

On the connector / cable problem I suggested, I expect they are just wires. But for example, what if one of the (two?) pins with the actual MAF signal is bent / wire broken internally / etc. but other connections within the same connector / harness / cable are still good. Could it be that the ECU gets enough to think the MAF is there and working, yet it's actually getting garbage or no data on that line? Smarter fault detection methods could help in this, but maybe they kept it simple (for once, LOL).

So I would start with a careful visual inspection of the connector, making sure all the contacts look good. Then the easiest thing to do to check for a wire issue is to get the car running (with MAF connected, so running badly) and wiggle the wire as far as you can see it, hoping you intermittently restore something to make it run differently. Think about where an internal wire failure is likely to happen - at the connector, bends, any place it may have been pinched, etc.

After that, it's trying to find the other end of the MAF connector wires, and testing continuity through the whole wire.
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Old 11-23-2019, 04:15 PM
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Ok new update for today:

While researching “resetting intermediate levers”, I came across some other N62 owners with similar rough idle and hesitation issues. Several of them mentioned that they unplugged their VANOS solenoids and saw much improvement.

I figured it couldn’t hurt...quick and easy. Noticed a couple of the outsides of the solenoids were caked in oil residue and dirt. When unplugged I could see that the inside of the connections were coated on wet oil.

So I left all 4 vanos unplugged AND plugged back in the MAF. It runs!! Stumbled for a brief second at start but quickly smooths out. Idles great. Took it for one quick test drive and it ran awesome - no hesitation at all!

Sooo I think I might be on to something. Could have been the bad VANOS connection all along?!

I replaced all the VANOS last year. Must have not seated one correctly or have a bad o-ring. Going to clean the connections and retest. I can swap back in the old ones if necessary as well.

Stay tuned...fingers crossed!!
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  #16  
Old 11-23-2019, 10:17 PM
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Quote:
Originally Posted by fishhouse4 View Post
I will check the connections on both ends.

The only two ideas my tech had was a new engine wiring harness (which would address those connections you just mentioned) OR a new DME. Both are stupid expensive...

Ok, help me here...this is what I don't get about the wiring/connection possibility:

It's just a wire, correct? It simply transmits the signal from point A (MAF) to point B (DME). Like... all or nothing, I would assume. So if the wiring or connections were damaged, then the signal wouldn't go to the DME. Which would be the exact same as having the MAF unplugged. So I would think in that case you would not get MAF signals to the DME regardless of if it was plugged in or not.

Or are you suggesting that the wiring/connections could be damaged in a way that could somehow degrade or corrupt the signal from the MAF??
Nope. Mass air flow sensor measure the amount of air going through it. How does it do that? It's a wire (or a film) that's heated by electricity and the air passing through it will cool the wire down.

The DME can setermine how much air is passing through the MAF base on the temp of the wire after it has cooled down.

Unplugging the MAF and the DME default to a preselected mixture base on the engine coolant temp and the incoming air temp.

I know on a 3.0 M54 engine the MAF is a Siemens unit, and not a BOSCH unit. Cheap MAFs on eBay or Amazon are known to cause more problem than what you save on buying them.
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  #17  
Old 12-01-2019, 09:51 AM
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Quote:
Originally Posted by fishhouse4 View Post
And this would only show symptoms when the MAF is plugged in?


Correct, the owner would unplug either MAF or valvetronic to get the engine to run until it warmed up. In his case, the motor would run ok once warmed up.


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