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Just coming across this glorious thread.

So if your block secondary air ports are clogged with carbon, which then kills your pump, is buying a replacement pump completely useless at that point and the only real solution to plug the holes up and tune the SAP out?
 

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Love this thread, finally finished making my way all the way through it.

The only thing I can contribute here is that I am in agreement that the massive carbon buildup on the original engine pics has to be from oil blow by on the piston rings. My wife had a 2001 E46 325iT wagon and she made many many frequent trips just down the street to bring the kids to school, to pick up something random, go to the store, we only live about 2-3 minutes form most stores. I am pretty certain that this exacerbated the known piston ring issue on the M54's and she had consistent oil burning on that car after we had it about 3-4 years. Opening up the valve covers on this car did show some carbon buildup around the vanos area, but the external vanos housing is a non-moving part and it was not a big deal there. Cams and lobes all looked totally fine and anything that would move a lot had zero carbon chunk like this, but I never inspected the piston heads or actual valves on that car. I assume they were pretty bad. I pulled the plugs once and it looked like the bottom of a shrimp boat they were so bad, almost like barnacles growing on the plugs! That issue turned out to be a bad crank sensor that was causing the car to run rich and toss carbon into the cats which ultimately destroyed the cats. Car would randomly backfire on the highway and it felt like the transmission was going to drop out of the car.

Plug pics for reference:



My point is, that car had many trips where the engine was not properly warmed up and that allowed the condensation to mix with oil and cause some sludge that likely contributed to the piston ring blow by issue and made it worse. BMWs in particular need to be warmed up good, the CCV system isn't necessarily optimal, but it's way better on the S62 than it is on an M54 engine.
 

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Here were the plugs on my 2001 E46 330i back in 2008 with about 120K on them, original plugs, minimal oil burn, just for comparison:
 

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hi all, well i just got the stupid low flow code, fixin to round up materials and get ready to perform the bypass. fingers crossed and hope it works, thanks sailor
 

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If it just popped up diagnose it. The code does not just pop up. It appears you clear it, then it does not show again for a bit. When the blockage is just at the threshold it will not be a constant code. If a vacuum line fails or your fan is weak, a valve is sticky then it will be constant, but those issues are sortable.
Good luck and don't forget just coding out the code is an option. Just because it does not work with my form of OCD does not mean it might not work with your version.
 

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I am about to pull the engine to inspect clutch and rod bearings. Car has 150k miles. I wonder if it is worth pulling the heads to clean out the SAI ports, get the heads rebuilt. What does a typical head rebuild cost? Thanks.
 
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