Since I have had my Ranger (185 000 km), it would always rev up to about 2000 sometimes 2500 rpm once started and then come back down to normal (1000-1500 RPM if I am correct). Now, the problem is that sometimes I will start the truck and it will want to die and then it kicks up to 2000 rpm. It only does that sometimes. Most likely when it is cold. Any causes for all these strange startups?

 

The IAC is responsible for maintaining idle speed & is a common problem part when it gets mucked up with deposits, so it belongs on your suspect list.
Maybe consider removing & cleaning it internally with a plastic safe cleaner like CRC QD, or MAF spray cleaner & see how it goes. Keep the little black cap part upright to prevent the cleaner from getting into the little foam filter underneath. Cleaning the IAC may not last, it didn't for me & is probably why Ford recommend replacement when they act out, but cleaning was a good trouble shooting step for me. Let us know how it goes.

 

I cleaned it last year in May. It didn't do much. I'll clean it again and if that does nothing I will get a new one. Also, it doesn't seem to have any gasket anymore. Is the IACV suppose to have a gasket (between the upper plenum and IACV)?

 

The OEM IAC has a black rubber "O" ring laying in a machined or cast in chanel on the flat mating surface in a sorta lazy 8 configuration. Some aftermarket IAC have a smooth mating surface & conventional paper gasket seal, so yes there should be some sort of seal there, or you'll have a downstream unmetered unfiltered air leak that the MAF sesnor isn't sensing & that'll mess with fuel trim & suck in unfiltered air, all a vicious circle, so get the IAC gasket question resolved asap.

While your resolving the IAC & gasket question, remove the battery B- cable to wipe the corrupt fuel trim & idle strategy tables. Then after the repair perform the base idle relearn routine here https://www.ford-trucks.com/forums/s...9&postcount=12, so the computer can quickly relearn its cold & warm idle strategy & begin to build new fuel trim tables without the IAC gasket air leak & the cleaned or replaced IAC valve & see how it goes.

If the IAC gasket is missing & has been for some time, I'd seriously consider an oil & filter change after getting things put right, as that unfiltered air leak will suck in plenty of unfiltered air, so your crank case lube silicon/dirt count will likely be high & that will wear away on moving engine parts, not a good thing.

More thoughts for consideration, let us know how it goes.

 

WOW!!!!! I've never though of that! I've been driving this thing without that little paper gasket as long as I've had the truck. I can actually see an oppening. Alltho, the lean codes are there since November 2012. Maybe this could explain the lean banks. I really wonder who removed the gasket. Strange things happened on this truck. The previous owner also did an EGR delete...

 

SO, your saying the IAC OEM lazy 8 rubber "O" ring gasket is missing????