Hi, I have a 1998 A4 with the 2.8 and recently, it has been running very rough intermittently. A lot of times, it runs perfectly normal but at random times for random lengths of time, it will loose power, run rough, and change to a much deeper pitch sound. It almost feels like a large intake leak post maf sensor. I thoroughly checked the intake from throttle body to Maf. I checked the maf connection. I checked the seal and the connection of the sensor further down the intake just outside the throttle body. I checked the breather hose connection to the intake just outside the throttle body. From there I checked over the entire breather hose system. The ENTIRE system. Also, I replaced every hose with 5/8" I.d. Heater hose that is much smoother and more durable than the ribbed oem plastic ones. I did this last spring. I then went over the ENTIRE vacuum hose system, which I also replaced with nicer vacuum hoses last spring. The ENTIRE system. With all that said, what could be causing the car to run rough and go back to normal at random for random lengths of time? Also, every time the car hit 5,000 rpm's, it will start running that way and then stop at its convenience. It does it at random when driving normal, but does it every time I hit 4 or 5,000 rpm's, then goes back at random. Some times it does it for a long time, other times not so long. But not once since it has started doing this, has it caused the car to stall or stop running. it just runs rough and weak and looses power and rpms wont raise and acceleration is very slow. Please help me with this. Thank you.

 

Can you get the codes pulled and post them for us along with what they indicate?

That would be most helpful.

 

It never wants to do it when I have a scanner tho. When it runs like that, the CEL blinks so I don't think it's gonna throw the error code when the problems not acting up. I need it to start misbehaving right as I pass an advance auto parts. Lol.

 

Have you scanned? I'm guessing no from your comments. Scan and post codes.

 

P0134 P1196 P1197 P0102 P1432 P0300 P0303 P0304 P0305

 

Are we supposed to know all the codes by heart...or were you expecting each of us to Google them in our attempts to help?

 

Sorry about that, Guru. Based on all your other abundant knowledge inposts in countless help threads, I really did think you had them memorized. Lol. Anyway, here we go.
P0134 - O2 sensor bank 1 no activity
P1196 - Slow response from oxygen sensor bank 2
P1197 - Slow response from oxygen sensor bank 1
P0102 - Mass Air Flow Circuit low input
P1432 - Secondary Air Injection Valve Open (this one has me the most curious)
P0300 P0303 P0304 P0305 Random cylinder misfire in cylinders 3, 4, and 5

 

P0102 MAF low. Next time your car runs bad, get out, open the hood, and disconnect the MAF. Report back what happens.

 

I agree. It does look like it could be a bad MAF. You could also check the MAF using Bentley manual testing procedures.

It might also be interesting to clear the codes, drive a day, and see what comes back.

 

To turbo: ok, I will, but what should I be looking for.
To Guru: P1432 is a secondary air injection valve open. When I googled it, it showed me a gold disc like object that I immediately recognized as a part on the back of each cylinder head that I plugged a vacuum line into. It looks miserable to reach with tools. Do those go bad often or is it more likely that all of these error codes are caused by a bad MAF?
To everybody else: Thanks for all advice. This is by far my favorite forum ever.