I have a 94 Formula A4 stock except for K&N CAI.
When I am stopped at a light after warming up, my car surges
from600 RPM'S to 1000 RPM's then drop immediately back down to 600 RPM's. This will happen quite a few times with no particular pattern.
If I don't keep my foot pressed on the brake fairly hard it will lunge forward.
One more thing the air is not on and it dosen't matter if its night or day.

Any clues?

 

Might check the map sensor on top of the engine,or it's connector.My02

 

i have been having the same problem. but i havent figured out what it is yet ether so sorry im not any help. hopefully i will have it in the shop soon.

 

Might try cleaning out your idle air control valve, also look for like a small vacumme leak.

 

check your 02 sensors

 

Thats what I was thinking. The IAC was bad on my car and Idle quality was very poor. It would be all over the place sometimes, and not stay running others, or run perfect

Definantly a PITA.

 

IAC first, or MAP. my .02

if not those, it could be a number of other things.

 

Might try this;spray ever so gently some carb cleaner into the little hole in the throttle body where the iac sucks it's air from,then(like cleaning a rifle bore),use Q-tips (Plastic only,the wood kind break off),and stick them down into the little hole one at a time and twist them as to clean as much black stuff out as possible.This may take one half a box or so,but see if this helps.Hey,do the cheap stuff first.My02
(Like cleaning a rifle bore I ment clean it till you can see no more black stuff)Hope this helps.

 

Or you could just spray the Q-tip itself,and do it that way.(Outdoors for ventilation).My02

 

I'd be willing to bet anything that it's the optispark.

My car was doing the EXACTLY the same thing that you described. We replaced the optispark while doing a waterpump swap and it hasn't surged again once since then. That was 1.5 years ago.

Not good news, sorry

Charlotte

 

Thanks for all your help.
I'll try the solutions you all suggested, starting with the cheapest first.
Again I really appreciate your help.