Running rough

02 jetta automatic w/ 195K mi starts and idles perfectly fine. When I put in gear and go it hesitates a bit then 'kicks in". When driving on the highway about 70mph and hit an incline i give it some throttle it again hesitates and then "kicks in" causing a huge cloud of black smoke.
The exhaust recently broke right after the cat converter, I drove like that for about 1K mi before I fixed it.
I am headed to Autozone to see if there are any codes, my check engine light is on but has been on for a long time before this started happening. I know I should clear the issue but after addressing the glow plug code a few times decided to live with the light.

If the MAF is bad I would assume there would be a code to indicate such?

I am planning to replace the air filter and noticed in the forums I should check the "snow screen". Where is this snow screen?

Anyhting else i should be looking into?

Any help is very much appreciated

Find a knowledgeable 'guru' close by, there have to be several.

The hesitation before moving on sounds more like transaxle hesitation than engine related. But people with more experience with autos will have to chime in. Suffice it to say the autobox with that many miles on that year car does not enjoy a reputation for lasting long; indeed people may tell you that you are extraordinarily lucky and you should start looking for a 5-sp swap replacement.

A bad MAF may give itself away with a code; however I would not want to predicate purchase of expensive parts on the reading from a non-VCDS (i.e. generic OBD-II) device. Get to the guru to find out what the real codes are.

The snow screen will be located in the tube that runs from the airbox toward the front, under/around the battery to the inlet at the top left of the grille. It tends to catch small bugs, twig pieces, sand, grass pieces, and anything else that gets blown in or sucked in and can't crawl back out on its own. The screen clogs, and then you have a pumping loss from the engine having to suck through a small door inside the engine bay with a spring loaded door.

If you just follow the tube out the bottom of the airbox, keep removing parts, you'll find it eventually.

Check for sticky vanes, sticky actuator, a leaky actuator, or leaky hoses.

The vanes are in the turbine housing, and its control arm with actuator assembly are mounted to the middle of the turbocharger unit, between the compressor and turbine housings. The whole assembly is integrated with the exhaust manifold. You can see the actuator through the space between the suction tube and the engine block, and you can easily fit your arm between the engine and the firewall to reach the actuator. Or, you can put the car on a lift/ramps and mess with it from below, where it's very easy to see/touch.

To isolate the actuator, a small spring clip attaches the vane adjustment arm to the actuator arm. Be careful when removing it, so it doesn't fly away. It works best if nudged off slowly and finally pulled off by hand, rather than prying it off completely in one motion. The actuator itself attaches with two 10mm (wrench size) hex nuts.

Also check for excessive clogging in the intake manifold. If clogged, it must be removed in order to clean it.


A VCDS performance test is very revealing in these situations.

I have codes
P0102 Mass or Volume Air Flow Circuit Low Input
P0402 Exhaust Gas Recirculation Flow Excessive Detected
Is this indicative of a bad MAF?