Just bought my 2000 Ford Ranger 2.5 a couple months back and tried to do some routine maintenance to it, but now it's not running well. I've changed the plugs and wires, flushed the cooling system, cleaned the ICV valve, replaced the PCV valve and thermostat, and replaced the hose to the fuel rail. It seems to want to die when it idles sometimes and when I shift into drive. I tried to adjust the idle but it constantly seems to be either running to rich or lean, and the exhaust manifold gets pretty red. This leads to another problem cause my temp gauge doesn't seem to move unless it's been running for like 45 minutes. All the hoses are hot but no heat is coming out of the vents!!!

 

Welcome to the forum


Start engine cold and pop the hood
Feel upper rad hose at the radiator end, should be cold of course
Let engine idle for 2 or 3 minutes then feel it again, should still be cold
If it is warming up with the engine then thermostat is not closed all the way, stuck open, which is what it is suppose to do when it fails, so replace thermostat.
Use 192-195degF thermostat
2.5l doesn't generate alot of heat so really needs the thermostat to stay warmed up.

After engine has been running for 10 minutes or so turn heat to hot and pop the hood feel the two heater hoses where they go into the firewall.
One will be hot the other cold, if heater core is clogged, or by-pass valve is bad
If both are hot then Blend Door in the cab is broken.

Dash board temp gauge uses a SENDER located on the drivers side of the engine towards the back, so gauge will read low but still should be above 1/3 when engine is warmed up.
Most temp senders are located near upper rad hose at engine end where coolant is the hottest.
These will read just below 1/2 at warm up

Once you solve the low heat issue engine should run better, so that is the first thing to do.

 

Did you put the thermostat in the right way with the little nib pointing either up or down? thats important. I think its a hole that allows small amount of coolant to pass thru.

Have you bled the air out of the system? easy way is to park on a hill and make it overheat so it boils over, or you can run it until hot then let it cool down and open the radiator cap and you'll hear coolant get sucked in each time

I also had a bad IACV and got one from advanced and it was WORSE than the one i removed! got a different one on ebay and problem solved as to the idle problems

 

also you're not supposed to adjust the idle, that covers up the problem usually...something is wrong if you're needing to adjust the idle screw

 

Hole in thermostat plate is called "jiggle valve", it allows air out while refilling cooling system, so should be placed at 12:00 position, where air would be if trapped behind the plate

No idle screw on fuel injected engines, looks similar but is called anti-diesel screw, and you are correct you should never adjust that screw for idle RPM reasons