012 AMM: engine stalls and runs very rich

Well I finally found the solution: relocating the amm from pre turbo to cold side intercooler did solve the issue. Now I would like to know why...? I do have to say that the turbo is pretty worn out and it's a cheap ebay one. But I never heard of a turbo thats leaks air or vacuum...the intercooler and the piping are fine.

I have seen many a turbo that leak, the backing plate seal on garrets and mitsu's are known to leak and cause issues.

Either way a pressure test with some soapy water can find all kinds of leaks.

If that's LH 2.2 try running lower fuel pressure such as BMW 2.5 Bar (actually 2.7 Bar) fuel pressure regulator.

thelostartof said:

I have seen many a turbo that leak, the backing plate seal on garrets and mitsu's are known to leak and cause issues.

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How could a leaky China-bay turbo cause an idle issue? Certainly I understand leakage under load, but not at idle when his turbo is far off the operating "islands". Anyone with specific experience about compressor side leaks, please share......

Directionally, I like the idea of the AMM right in front of the intake on the cold side of the FMIC...... makes me wonder why the factory engineers didn't do it that way (as on the NA versions). Certainly they had their reasons.

Is the OP running an IAC valve, or not? I missed that detail.

DET17 said:

Directionally, I like the idea of the AMM right in front of the intake on the cold side of the FMIC...... makes me wonder why the factory engineers didn't do it that way (as on the NA versions). Certainly they had their reasons.

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I know as the oil starts coming from your turbo it'll make its way onto the hot wire scewing the readings or potentially damage the wire. 012 amms aren't the cheapest either (compared to 016s)

Maybe just clean it way more often if your turbo is leaking a little oil.

Yep, It does have a AIC valve.
The intake system is checked for vacuum leaks. Found a couple of small leaks and the backing plate seal of the turbo was the only one I was not able to fix.
However, I really dont believe this small leak made the engine running so badly. Most leaks I found were there probably for years and I never really noticed them (i do have a RSI cam which is a bit lopy on idle).
Now I read on some import forums that it does matter how far your AMM is located from your turbo compressor house. In my mind it doesnt makes a lot of sense though.
Does anybody have knowledge or experience with the AMM being too close to the turbo and causing issues because of that?
Im just trying to understand this situation.

My tune changed when I swapped from the original airbox to a K&N filter, even when I had a long section of tubing between AMM and filter.
It could have to do with a change in the velocity profile in the tubing, altering the reading of the AMM.

For example: a bend directly before AMM gives a different reading as a longer straight section at the same airflow. At least this is my experience.

The AMM is really sensitive to differences and can change AFRs a lot. I suppose the chips were burned with the AMM on the hotside after that transition coupler seen in the first pic?
I use a similar coupler system on my 012 AMM, but on the cold side, with the stock air box and bend. First, I had mounted the coupler a bit too "deep" on the bend by mistake, so that the smaller diameter pipe continued 1-2cm in the larger section of the coupler. The chips I used were made custom for the car with this setup. I noticed my mistake when changing the air filter and then shortened the bend pipe so that the transition to bigger pipe size was where the coupler actually gets larger, so 1-2cm futher away fram the AMM. My AFRs changed drastically and had to get new chips.
So the only thing that changed that affected the AFRs was the length of bigger diameter pipe before the AMM and got the car running correct AFRs with the new chips.

All of us Engineers learned, when discussing compressible flow, that "the system determines the flow, not the fan (turbo)". I have no doubt what you describe is absolute truth..... you've changed the system on the suction side of the turbo (fan). Once the system is established "fixed", then the fueling tables would be adjusted to match those conditions and provide optimal AFRs.