So my B5 a4 has been running really rough as of late. I took it in to get the codes scanned and autozone told me it was an issue with the idle control valve. Having a 1.8t I can't find any mention of an ICV in our cars, and so I did the suggested cleaning of the throttle body, but I am still have issues.

When I push the gas pedal down, the car will rev to about 3500 RPM and then lose all power and go back to a low idle at 500 RPM and keep jumping up and then back down in a cycle. If i floor it (clearly not good at this point) it will go above 3500 RPM and I can engage the clutch and drive. If at any time I drop below 3500 RPM the car loses all power and slowly decelerates until it stalls, or I can push in the clutch and try to rev the engine back up, but again, clearly not good for the car. I have like I previously said cleaned the throttle body, replaced all the vac lines, spark plugs, even gave it an oil change, but I am out of ideas. Obviously I missed the smart opportunity by not getting the exact code number from autozone, but Iwas wondering if anyone had any ideas.

Thanks

 

O2 sensor, maybe?

 

I'm wondering if the TB is misaligned - it can't hurt to do a throttle body alignment. It could also be the throttle position sensor going out on you (although I figure that'd throw a code).