I recently purchased a 1999 A4 2.8L Quattro Avant with 49,XXX miles. It had been sitting since 2008 and I've been able to get it up and running with a minimal amount of repairs so far. I'm still running into one problem that I need some help with. And first, if this is already a running thread, I apologize. I don't intend to create redundant posts and made an honest effort to see if this topic had been addressed.

When driving at speed (no particular speed) and the car begins to go uphill, the tach will bounce. Not very much. Maybe 100 revs. I can feel the car bouncing as if I'm tapping the accelerator. Also, when accelerating such as on an on-ramp the car sometimes seems to "stick" at about 2500 RPM's, but only for a second or two and then powers through. The two problems seem to be related. I'm decently handy and hoping this is something I can fix myself.

I honestly appreciate any advice that you might be able to give. This is my first Audi and I'm glad to have the generous help and expertise of this community.

If I've left out any pertinent details, I'll gladly post whatever may be required.

 

Do you have a vag com or do you have any codes? Sounds like it could be as simple as a vacuum leak somewhere to me....or it could be something worse, but if you had some codes, it may help.

 

I apologize for not getting back to you sooner and I appreciate your input. It didn't throw a code until last night. P0411 (evaporative emission incorrect purge flow), which I've come to find means there's an issue with a solenoid that's located near the air filter box. However, I don't think that this is related to the bouncing tach. Unfortunately, there are no other codes that were listed on the scan tool. Any further thoughts are greatly appreciated.

 

The code is related to the SAI pump...has to do with emissions....usually when they go bad, or the pipe/hose is disconnected or there is a leak, the rpms increase on their own up and down (engine is louder etc...but stops when warmed up)...it's NOT what you are describing, but it could cause loss of power (like you said going uphill etc) and your idle bounce as well if you think about it (vacuum, clog etc). It may just be your hose came off...but who knows...

Here's a link to a SAAB, jerky idle, cruise shutting off etc...almost like yours...and it's related to the SAI pump or check valve.

Issues Connected or Same Problem? Slipping, Cruise, P0411 [Archive] - SaabCentral Forums