Hello, ive been driving the wheels off the plymouth now that the weather is getting nice. ive tuned the car but lately noticed the mileage is not what it had been , as well as the trans doesnt seem to kick down when i step into it. Is this a symptom of a faulty vacuum advance? Any easy way to rule this out? Also checked all the hoses which appear to be intact.
Thanks in advance. RUSS

Trans kickdown is via mechanical linkage, and based completely on how far the accelerator is pushed — nothing to do with vacuum. If your trans won't kick down and you've got sluggish performance and reduced economy, your kickdown linkage is likely maladjusted or disconnected.

A dead vacuum advance will certainly cause poor performance and lousy mileage, but it'll usually also create driveability faults (pronounced hesitation/stumble, etc.). Easy enough to check this; disconnect the advance hose at the carb end and suck on it. If you can suck air (won't hold a vacuum) then the advance or its hose is faulty and needs replaced.

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