Mass Air Flow (MAF) question for replacing
 

So I replaced my MAF on my 2002 Audi A6 2.7t. And it did not fix the problem of hesitation and jerking and bouncing within a range of RPMs.

When I had it unplugged it worked fine. Is there anything special I must do when replacing with a new MAF? I did disconnect both battery terminals is there anything I must do when putting a new MAF on my car?

Keep in mind the old MAF was doing the same thing. If I unplug the MAF it works a lot better and smoother almost normal.

Thanks

Definitely check for vacuum leaks and I don't think you can completely rule out that the new one was good (I'm assuming it was used?). Or who knows maybe the connector/cable is bad? Make sure to clean all the contacts and look for bare wires.

Boost leak.

Do you mean a leak by the turbo boost?

You have a large intake leak after the MAF, so any of the intake plumbing, intercoolers, crankcase ventilation system, or intake manifold leaks will cause big problems. Disconnecting the MAF makes the engine run on preset values and leads me to believe its something between the MAF and throttle plate and not a manifold vacuum leak.

Ok, got some of that. I disconnected it again and runs 10 times better.

Possible places I could check for leaks? I do not have pressure test system. Could I use smoke from a cigar? Any suggestions?

Trying to get my hands around what you said. So with preset values even with leaks how does that happen to still run smoother with MAF disconnected? Should I try cleaning the new MAF I received? Or return it for another new one from where I got it? The error codes I am getting are P0103 and P0175. MAF error and system 2 rich bank 2.

Now my car has 155k miles, should I be concerned about the Diverter valves and N75 valve? Change those at this mileage? are they known to go?

Thanks for the help.

So the MAF reads air coming through the intake to the engine. If the engine pulls air through a different location, like a boost hose blew off under the car, then there will be no/lower MAF signal, no MAF signal, you get codes and poor running. You unplug it, then its running on preset values, not being fooled by the lack of MAF signal.

Actual engine vacuum leaks really affect mixture directly, so even on preset values it may run too lean and run poorly. Doesnt mean thats its impossible though

Ok that makes sense.

Being I don't own a pressure test system. What "DIY" could I use to help determine where leak is? Also do you think at a 155k the Diverter Valves and N75 should be replaced regardless? DO they last a long time?

Thanks for the help and understanding.

Agreed...check for leaks and codes with VCDS. Had the exact same symptom so I purchased a new hitachi maf (now I have two because I went to a larger MAF so I have the original MAF, and a brand new Hitachi). Found it was a simple boost leak. The intercooler hose blew completely free.

Search and you will find a cheap DIY on how to test for boost leaks. You used a 3" rubber plumbing coupling, a 3" pvc cap, and a compressed air hose fitting. Very easy and cheap.

Just check all the boost hoses. There are ones from the turbos to the intercoolers that blow off and loosen up the clamps. Theres hoses from the top of the intercooler to the throttle body, theres the big Y intake on top of the engine with the DVs plumbed in. Dont just look, grab and try to pull on the rubber pipes.