180q

The reason that I ask is this: I took my Mass Airflow Sensor out, and thought I was cleaning it. I put it back in, and went for a test drive. The car isn't making anymore boost. It just peaks at a certain point, and just stays there. The revs also dip pretty low when coming to a stop. Any ideas?

Thanks,
Chad

Audiboy

as in any Audi cars (using later MFI and Bosch Motronic) to determine how much air is going into your cylinders, along with some temp sensors to recalibrate the density.

No MAP (manifold air pressure) sensor on these cars regardless of what other folks may tell you. So, if you took away the functionality of a very important piece, then chances are your car is running in limp mode, a fixed program to get you home and based on throttle position sensor only. No boost, just a slightly rich mixture. Now, you don't have a check engine light on? BTW, not a good idea to touch that MAF. That thin wire is quite fragile to non-careful hands, plus it comes with it's own dust burner on shutdown.

Style12v

My guess is that there would be an engine light on if your MAF was broken. I don't know from experiance, and the manual doesn't say anything about it...

If you are in limp mode, which would probably be the case if it was broken...
I don't know about A4's, but on my A6 you cancheck it by seeing if cruise control works, if you can switch into 1st, 2nd, 3rd gear (on an automatic tranny of cource)

If this isn't the case for A4's, it should mention it in your manual.

xr4tic

I don't think it ever needs to be cleaned. The ECU determines boost by checking the readings of the MAF. If it gives off readings that are too high, then you wont have any (or less) boost.

also check your vacuum lines going to the wastegate and frequency valve. Maybe one broke or got knocked off.

dingster

Most MAFs are just a glowing wire. It determines the mass of air going pass it by detecting the resistance through it due to the air cooling the wire. I think on most cars with MAFs after you shut off the engine it glows to a very high temperature to burn off any oil or residues on it much like self cleaning ovens. I don't think it's a good idea to clean it urself.

It may very well be the cause of your drivability issues. At WOT the ECU determines timing/boost/fuel based on the reading from the MAF and some other sensors. It could affect drivability dramatically.

Audiboy

Yes glows red after as you said, so I called it a dust burner