My car has been weird ever since the swap over a year ago. The engine has a reletivly new optispark and i just replaced the plug wires. It idles very good and runs even better. The problem i am having is when sitting at a stoplight it will sometimes just totally bog out then the rpms will almost imediatly come back up and the car will launch forward. It kinda scares the crap out of me when it does it. Also, on decel i can kinda feel it do a more subtle chug. This is an A4 car and thougts of the tranny causing this are starting in my head. Could this be or should i just slap a new opti on it first?

 

what stall do you have?
what kind of tuning?

 

Could be a vacuum leak. Hows your vacuum?

 

Stock stall, custom tuning done locally. Just started doing this about a week ago when i got it out of storage.

I will check the vacuum today. That is a possibility!

 

Could be a motor mount. If you've got a broken motor mount, this can cause the car to just launch forward.

 

I had the same problem,sitting at a fast food drive through,and all of a sudden,the car has a mind of it's own,reving up ,so I throw it in neutral,then it comes back down.Didn't happen for a while,then it did it again,so I say,screw this,took it to the dealer,and guess what?,the wires on the pass side of the manifold were toast,leading up to th iac,and map sensor,so $150.00 later,problem was solved.Been a year now and everything is good.Hope this helps.