I have been troubleshooting an issue with my 2000 ranger 3.0 flex fuel. Since weather turned colder my ranger when it's 10 above or lower doesn't want to start properly and I end up having to flutter gas pedal almost at floor. Changed fuel filter full tune up etc. I am no throwing any codes. Cleaned mass air sensor. My IAC valve is working as I pulled wire harness and engine dropped to 500 rpm however I remember the truck idling higher on cold start and then dropping as engine warmed. That higher idle is not happening and engine has intermittent sputtering have to rev it to keep it clear. Seems like I'm running lean but fuel pump is good and new filter so I'm stumped.. help plz

 

Does it run normal after it's warmed up.
From what you described, it sounds like the coolant temperature sensor is failing, or failed.
It looks similar to the gauge sender, except that it has two wire coming from it, not one as for the gauge.
Be sure and get the correct one, as they look very similar.

 

thanks for responding Jeff. having some issues with it even when warm but mainly at cold start. As i had mentioned its fine above 15 degrees for starting but still has a sporadic misfire but its subtle i have done a complete vacuum diagnostic on it and all of that is good. I did replace intake vacuum hose for pvc. I too have been suspicious of the coolant temp sensor.

 

You may want to replace it just to get it off the table, it's not expensive.
Rock Auto has them all mixed it with the gauge units, some are listed as senders, switches or sensors, you want the one listed as "sensors".

https://www.rockauto.com/en/catalog/...+/+sensor,4748

 

Thanks Jeff i will replace it to eliminate that possibility but still baffled about the issue sporadically doing it after engine is at operating temp. Air fuel mixture issue it seems like but if that sensor is wacked out the computer is trying to sort out fuel based on coolant temp. I ran full vacuum check to rule out lean out due to unmeasured air intake.

 

Ok so i replaced the coolant sensor and truck started at 2 below farenheight.. Progress indeed but i still dont have a higher idle which i should have. Is the IAC valve still having a problem altho it checked out in diagnostic. ???

 

When the truck is cold, remove the IAC valve and note where the position of the plunger is, have it plugged in and have a helper turn the key on.
You should see the IAC valve move significantly for high idle.
They can and do get dirty/sticky.
Some here have used brake cleaner with some success.

 

The ECT sensor tells the computer how much Choke to use to start a Cold engine, all gasoline engines need to be Choked on cold start, Choke means extra Rich fuel mix

The IAC valve is used by the computer to set idle RPMs, cold engine would usually idle at about 1,100rpms
The computer will open IAC Valve all the way with key on, warm or cold, this is why any fuel injected engine should REV to 1,500rpm or so on start up then drop to "target idle"
Computer has a temp/idle list, i.e. 1,100rpms if temp is under 80deg, 900rpm if temp is under 140deg, 700rpm above 140deg, these are target idles, and examples, not exact, lol

If you think your idle is low when engine is cold, there should be a code set in memory, because computer can't raise idle to target level, this doesn't always turn on CEL

Yes, your IAC Valve is closing all the way when unplugged, but that doesn't mean it can open all the way

 

Thanks Ron. Tomorrow ill be spending some time on that IAC as i too feel its not opening all the way. I will also be checking throttle assembly idle set screw spring as i know they can get weak altho im sure IAC doesnt use that as far as what ive read. I may just replace IAC if i cant sort this. Thanks again Ron for the guidance. Mike

 

If you decide to replace IAC Valve only use Motorcraft(ford) brand, I have also read Hitachi IACs will work on Fords, but no other brands do

 

Update. Was sucessful today unlike last week finally got a code P1504 which confirmed IAC valve. Changed it and computer relearned and truck is running perfect. Thanks again to Ron and Jeff...

 

Thanks for the update, glad you got it sorted !