Ok so i have a 92 ranger 2.9 liter, and when it idles (especially when the engine is cold)the engine surges, like my rpms go up then down, and repeat, if its cold it will sputter out and die so i gotta restart it, it still does it when warm just not nearly as bad, plus when the rpms drop my battery gauge drops to, its not my alternator belt ive replaced it, anyone have this problem? I was told maybe its my timing, but i really dont know, let me know what you think, and how much it can cost

 

Clean the IAC(idle air control) valve
google: clean iac valve

Warm up engine, let it idle and disconnect the IAC Valve wires, idle should drop to barely running or engine may even stall, either is GOOD, it means no vacuum leaks.
If idle stays high then you have a vacuum leak.

After that check the spark timing, you need a timing light and you need to find your SPOUT connector, it will be near distributor passenger side
Google: ranger spout connector images

Engine needs to be warmed up, and off
Hook up timing light
Disconnect SPOUT
Loosen bolt that holds distributor tight, at the base of distributor, just needs to be loose enough to rotate distributor.
Start engine.
Set #1 spark timing at 10 to 12deg before TDC mark

If idle is still surging when cold the you will need to replace ECT sensor, $7.
Fuel injected engines have TWO engine temperature devices.
ECT(engine coolant temp) sensor, has TWO wires, only used by computer

ECT sender, ONE wire, only used by dash board temp gauge.

You need to change the TWO wire sensor

They are located near each other above thermostat housing