89 Crown Vic idle surge

I have a regular, pulsating engine speed surge at idle. It occurs only when the engine is at operating temperature. The idle air control valve has been replaced. The engine is a 5.0 liter and is a California gasohol experimental vehicle according to the emmissions label. Any suggestions on a cure?

If it's a special vehicle, i'd see if you can't trace down the folks that made it a special vehicle and ask them what they would suggest. If it's a regular 5.0L i'd have the idle checked, it may be a little high.

If it's a carburated motor (but i think they had done away with carbs by then?) then i'd say ur butterfly valve on the carb is sticking.

Hope that helps somewhat...

I have had a problem with the MAP sensor which is located on the passenger firewall. You should check that the vacume line is not leaking. A quick fix a mechanic friend told me about was take the handle of a screwdriver and give the map sensor a rap. If the MAP is the problem it should stop surging. if not make sure the IAC wires are plugged in, I have had a car where the plug was bad causing all kinds of problems. As far as a special vehicle, and that it was a test car for gasahol I doubt thats the problem, most gas has up to 10% alcohol in it. I did buy 2 Methanol fuel cars from the state, and there was no difference, I even used the computer from those cars on others.