I have a Canada model 1992 Ford Ranger, 4WD, 2.9 L V-6, A.T., (no A/C), about 110,000 miles.
Had the truck 2 years and couple of months ago began to idle like the engine has a high performance cam in it, it lopes up and down and up and down about 300rpms.
I have replaced the IAC, the TPS, and sprayed either all over the vacuum lines while the engine is running in order to try and find a vacuum leak.
Brand new spark plugs wires distributor cap and rotor about 10,000 miles ago. This truck was made in Canada and does not have a MAF sensor.
I need help to figure this thing out!!! please.

 

Welcome to FTE.

Will see if I can get things started. Good vehicle detail, maintenance & trouble-shooting info that might help figure in on the anomaly.
Did the problem come about suddenly after some event???

Scan for trouble code clues & post All code Numbers as they can also help focus a trouble shoot.
This year/model is OBD-1 diagnostics, so you don't need a code reader, or scan-tool to retrieve trouble codes but they do make it easier, faster & more accurate to come by any pending or set trouble codes & a scan-tool can also provide live data which is helpful on a trouble-shoot. I have & use a Actron CP-9145 in my CP9150 scan-tool set, on my 94 OBD-1 Taurus under hood DLC, to retrieve codes & monitor live data feeds that sure have helped trouble shoot its woes over the years.
You can also use one of these wiring hook-ups Ford OBD/OBD2 Codes – TroubleCodes.net, to come by any pending or set codes & they will have the in dash check engine light blink the codes, or the added in lamp, analog meter, or 12 volt buzzer blink, wave, or sound the codes & might be easier to get more accurate numbers that way, if you have problems coming by a code reader, or scan-tool that'll hook up to your under hood OBD-1 DLC system connector.

EDIT: Forgot to add this link for some good input on OBD-1 systems that has come in handy on the Taurus, Ford Fuel Injection » Home (archive.org)

Some initial thoughts for consideration, let us know what you find.

 

Ive got a similar issue, been trying to track it down on and off for years. I've brought it to mechanics and tried to get the help of people on ford forums like this and everyone always ends up stumped. When does the idle surge? When its warm? When its cold? All the time? In park or in drive? both? Mine only surges while warm and idling in park.