Upon the initial startup the idle is erratic and surges up and down for about half a minute then idles smooth at a bit higher idle for another half minute. It makes restarting after driving sometimes finicky to restart. Normally not but sometimes. I'm at a loss to find the source of this erratic idle at cold startup. I've been driving this truck since 1998 and it's never done this before. I gave it a change of MAP sensor and idle position sensor plus checked the fuel pressure regulator and idle control. Any ideas on what to check next???

 

I would check for OBD codes and inspect for vacuum leaks. Also, do you know how many miles are on the oxygen sensor? When cold it should be ignoring that because it’s not sending a signal, but still could be an issue. Have you looked at the spark plugs and compared them to photos of rich, lean and about right?

 

Well I thought of a vacuum leak but the surging/odd idle quits after about a minute of higher than normal idle. Then it idles just fine. The O2 sensor was changed recently a long with MAP sensor and the throttle position sensor and I cleaned the throttle body plus inspected the idle valve. This truck has been a steady performer for 27 years and still gets 20 mpg. I bought it from a dealer when it was 10 years old. It's always started by just turning the key. Now I have to give it a little throttle before turning the key then let up on throttle once it starts.I gave it a tune up not that long ago when issue began. I have 3 more Ford trucks and I do all the work on this one myself. It's sort of a challenge to keep it running and my friends say to junk it. The other trucks are older trucks and I have a hard time thinking about a newer truck. No one can recommend any of the newer trucks. The newest one is a 2005 FX2 Level2 Ranger and the others are both F350's. The F350's are like driving an aircraft carrier into grocery store parking lots plus I like an old beater for hauling dirt, gravel, and long lumber.
I'm starting to think I may have to live with the issue till something more definitive developes.
Thanks for the input. The mental rease goes on.

 

If it won't start with your foot off the throttle but it does when you give it some throttle, it sure sounds to me that the idle valve (IAC, ISC) isn't opening when the system is in crank mode. Maybe you don't have enough voltage when cranking (battery is shot, starter brushes are worn down and it's hogging all the battery power?). There should be a way to test if voltage is normal. The IAC may also just need a cleaning, the whole intake gets pretty gunked up from crankcase ventilation.
The attached images are from a book on The Ranger Station about the EEC-IV system. There are tests specific for the IAC solenoid and the circuit. Note that DMM stands for digital multimeter. KOEO for key on engine off amd ER seems to be engine running.

 

You may be on to something. Over the past year the Bendix for the starter has had trouble kicking the gear out far enough to engage the flywheel. Maybe the 37 year old starter needs to be replaced. The battery and alternator are both up to snuff. I'll do some checking on that idle valve issue. It sure runs good after a minute of running. I never thought there was a voltage issue to the idle valve solenoid. I checked it out in a static setting and it seemed to power the solenoid just fine. I'm just amazed how sturdy these older machines are compared to the newer vehicles. This old ranger must have 400 K on it. Rebuilt the front axle spindle to spindle back in 06 and changed the water pump and clutch as they wore out Still hauls a lot of riff raff and is great in 4x4 in the winter here in Alaska. From what I read and see in the media, the new generation of trucks are junk and all have inherent problems. My old 96 power stroke is a hard one to replace. The new diesels are all iffy.
Thanks for the input.

 

I don't think these early ranger starters use a bendix. Check out this video and note how he talks about these starters using a lot of battery current. I've got about 260k miles on the original starter but I know the brushes have worn down to about the minimum thickness (see image). A brush set can be purchased for about $20 and it's not a big job to pop off the back of the case and have a look.