Mazda truck - high idle speed

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Have a '92 Mazda B2600i (not a ranger clone) w/79.8k miles on it. Few months ago, had problem with intermittant stalling. Had a new Idle air control bypass valve put on. Also at the time had thermostat, and fan clutch replaced. no more stalling, but....

Now engine has started idling high, intermittantly. When first started in morning, it blasts to about 2000 rpm, then slowly comes down to about

1500. Stays there for a few minutes then seems to settle about 1000. Manual says about 750 is normal, i think. It will vary, however, between 1000 and 1250 for duration of drive, no matter how far/long. (note all rpm notes are from tach on dash). I also note that if idling and fan is not on, when turned on rpm increases by a couple hundred, tho not every time. If idling with fan/ac on, then turning off, rpm barely and rarely goes down. Of course, gas mileage is down. On occassion, it will idle just under 1000rpm, then slide up to about 1200, whether accessories are on or off.

Is this just a matter of adjusting idle speed? or more serious? New TPS needed?? or somthing else entirely?? (like a new truck??)

Thanks for your help.

-- Regards, X

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