Triumph Repair: Very low mpg, idles high at 1500, poor mileage, spitfire 1500

Question
My '76 spitfire 1500 idles at a high 1500, i was lead to believe it should idle around 950? how can i achieve this? Also it is getting a lowly 10 to 15 mpg, this is very saddening as i bought this car to drive to college and work and i barely can get back and forth without refilling its small gas tank. What are a few suggestions for increasing my mpg?

Answer
Hi Sam,
1500 RPM is too fast for an idle which may be caused by many things.
A sticking throttle pedal, cable, linkage or a problem in the choke system.

When the car is warmed up and idling at 1500 RPM have someone give the throttle a few quick blips to a higher RPM while you stand behind the car looking at the tail pipe. If you see puffs of black smoke then the choke is most likely the problem with the fast idle and the poor fuel mileage.

As you know fuel mileage is affected by driving conditions but even poor conditions should net you a lot more than 10 to 15 MPG.

If your choke was not the problem you need to have someone do a test of the engine and the ignition and fuel system.

When I was brought a car for just poor mileage I had to first run a compression test then adjust the valves and set the ignition timing accurately and after all that was corrected, Then and only then would I adjust the carburetor. That is the only method I know to get what ever fuel mileage that car was capable of.

Howard