I have a 1992 Ranger with the 3.0 engine, automatic, and about 80,000 miles. It generally starts fine and runs great hot or cold except for one problem that started recently and is happening about 95% of the time. Otherwise a great truck since it was new...

When the engine is cold even if it's 75 or so outside, it starts fine and the idle immediately goes to 1200rpm or so but then drops to about 300rpm and surges back to 1200. It does this several times, then stalls, unless I hold the throttle open enough to get it above 1500rpm, then it runs smooth. If I then lower the rpm to less than 1200, the surging starts again. If I can get it in gear without stalling, it runs great after a 1/4 mile or so, even if the engine is still cold. When hot or after sitting for 3 or 4 hours it still runs fine. This started suddenly and has been very consistent for a while now....

If it stalls, I usually have trouble getting it to restart, and I've found it restarts best if I open the throttle while cranking for 10 to 20 seconds, as if the engine flooded, but no obvious black exhaust smoke...

I'm guessing it's related to the throttle body, an air temp sensor, the throttle position sensor, or the idle air control valve. Resetting the computer by unhooking the battery didn't help, and a new air filter didn't help either. Neither did reseating electrical connectors to the throttle body sensors & valves. Haven't cleaned the MAF sensor, idle air control valve or anything else yet. Any thoughts or suggestions??

Thanks in advance

 

Welcome to FTE!

Try pulling the codes, you don't even need a scanner:

http://www.thorssell.net/hbook/eectest.html