I have a 1975 914 2 litre that has just come up with a new problem that includes stalling during idle and hesitating while driving. Seems to only happen when engine is cold.

A little history on the car first. Vehicle has 35000 original miles and is completely stock other than a pertronix ignition system and the removal of the air pump system. Fuel pump is new and fuel filter was replaced within the last 2000 miles. Gas tank has been professionally cleaned and does not have any rust issues.

Just recently took the vehicle on a 1200 KM 3 day vintage car rally where it performed flawlessly. 3 days of hard driving through the interior of British Columbia with all sorts of vintage vehicles was a blast.

Now 2 weeks later its developed a bit of a problem. When vehicle is first started it seems to idle smoothly but if I let it sit and idle for a a few minites it will occassionaly stumble and possibly stall. It will start right up again and continue this pattern. Once vehicle is warmed sufficiently the problem seems to be gone.

Suggestions?

Does the engine do it's normal high idle then stumble when dropping to the 950 range? or what?

Vehicle's high idle seems to be working normally. Stumble or stall happens when it's come down to it's normal idle range. What would be a normal time for the high idle?

Depends on temp. Here is Socal 4-7 min's from dead cold to first drop on AAR valve. Where you are, I honestly don't know......10-12 min's? Are you saying it won't stabiolize at about 950 rpm after the idle speed drop?

Vehicle idle definitely won't stabalize around the 950 range. Would a faulty AAR valve cause hesitation when driving before engine has reached proper temp? I don't think my high idle has ever stayed on for even the 4 - 7 minute range.