I have a 200 Ford ranger XLT 4.0 and for the last week and a half it's cranked up hard and not wanted to stay idled. But if I put my foot in it and keep the engine goin and have my foot on the brake it will run okay. After a few mins on the road it goes away, and it's no where near as bad as it is on start up. Now I have noticed in my driveway if the front end is slanted upwards a little bit it will crank up fine and not have a problem. I've changed the fuel filter, throttle position sensor, throttle position valve, put seafoam in it and I'm about to check the MAF because it says the same symptoms I'm having on my ranger. If anyone's got any idea of what it could be I'd truly appreciate some feed back.

 

Welcome to the forum

Assuming a 2000 Ranger?
So a 4.0l OHV engine

2001 and up Rangers used a different 4.0l SOHC engine

Could be fuel pressure, cycle key on and off 3 times then try to start engine

Could be ECT sensor, it tells the computer when to Choke the engine, and how much Choke, based on engine temperature on start up, not an expensive sensor

IAC Valve(throttle position valve??), is used by the computer to set high idle when Choke is on, these can only be replaced with Motorcraft IAC Valve, 3rd party will not work

 

Its a 2000 ranger. And just asking why do I need to go back straight with motorcraft? Is it just a default in the ranger? And what is the ECT, I'm a learning mechanic and Im still trying to learn all I can.

 

Ford brand is Motorcraft
Like Chevy is Delco

There have been many complaints the 3rd party IAC Valves don't work well, wandering and high idles, and because its "new" people end up chasing their tails trying to fix a problem they just caused themselves, lol

ECT(engine coolant temp) sensor is used by the computer only, it tells computer if engine is cold so it will Choke it and run a higher idle until it warms up
Its a 2 wire 5volt sensor
If the ECT sensor was telling the computer the engine temp is say 160deg, even though its 50deg then computer would just think its a re-start(ran into the store) and engine would run very poorly until it got up to 160deg

There is also a 1 or 2 wire ECT SENDER, it is for the dash board temp gauge, its a 12volt sender, they look similar but are not the same
Sender will always have a red/white stripe wire, so if you see that its the wrong one to change, unless dash temp gauge stops working, lol