I have a 2000 ranger 4cyl (dual plugs) 5spd 2wheel drive,when I start it it will idle fine then when I take off and stop at the end of the block it starts missing real bad . It does this at every slow down or stop till it gets warm and then idles great. At higher speeds it doesn't (when cold ) do it. After it has run 10 mins or so it seems to run great
I have changed filters - IAC valve.
Any ideas?

 

Fuel injected engines can't use Choke Plates, but cold engines still need a richer fuel mix, advanced spark timing and higher idle.
So the ECT sensor was added, ECT = engine coolant temp

This is a TWO WIRE sensor, not to be confused with the 1 wire Sender used for the dashboard temp gauge.

Normal cold start without touching gas pedal
Engine starts and RPMs go up to 1,500+
Computer has opened IAC valve all the way for starting
Computer closes IAC valve to set COLD idle, about 1,100rpms
1,100 rpms is set by ECT sensor temp, colder temp higher idle, warmer temp lower idle

As engine/ECT sensor warms up idle will slowly drop to 650 on manual, 750 on automatic

If your engine is doing this then ECT sensor is fine, if it isn't then change it, under $8

If ECT is telling the computer engine is always warm, like you just stopped at the store and restarted engine, then it would run poorly until it actually warmed up

On lima 4cyl it is usually on the drivers side front, below intake

 

Thanks I will try this

 

put in new sensors for ECT and sending unit stills misses. It will start and idle fine and it seems if you drive real slow the first 4-5 miles or 8-10 minutes it does okay. If you take off normal it runs fine thru the first 2-3 stop signs then when you come to the next one and push clutch in it starts to miss sometimes so bad it dies.
After 10 minutes it seems to run just fine no issues.
Please anymore suggestions

 

Hit an auto parts store and get them to read the codes, it will have current and history codes, WRITE THEM DOWN.
That should tell you if computer see a problem.

And it is possible you just need to clean the MAF sensor, on the 2000 it serves two purposes, air flow meter and air temp reader

 

Have cleaned the mas sensor and it's not showing any code

 

That is odd, unless recently cleared the computer should have a few history codes?
Does the CEL(check engine light) come on and then go off when key is first turned on?

Try unplugging the MAF sensor and then starting the engine, the CEL should come on fairly soon after.

 

the CEL comes on and goes off when started , I have never seen CEL since I've had it (2 1/2 years) and two people have checked it with hand held devices and said it showed no codes. The dealer I bought it from did mention something about having to order something to clear a light . I had heard that rangers were bad on some co2 sensors so I figured that was it.
I did unplug the MAF and let idle for about 7-8 minutes and CEL did not come on but it did idle rough.
What is weird is if you start it and let it idle it does fine, it seems when rpms go up and come back down to idle (at stop sign) is when it starts missing.Then 4-5 minutes later it smooths out and runs good. Starting and stopping while it is warm there is no problems.

 

If you don't get a CEL with a main sensor like the MAF unplugged then there is a computer problem.
Can't see any way around that.

That's what the CEL is for, computer uses voltages from sensors to operate engine, when a sensor returns voltage that is too high or too low CEL will come on, when there is no voltage CEL should come on pretty fast.

 

Haven't had chance to get to dealer but have noticed something weird / odd about ranger problem-- if I stay under 3000 rpms the truck runs FINE. Yeah ,if I stay around 2500 rpms in the first 8-10 minutes of operation it will not miss a beat when I pull up to the stop signs coming out of subdivision . So it seems if I go over 3000 rpms and slow to 2500 or under this is what causes the missing /sputtering , again the truck runs fine after 8-10 minutes . Could this be the throttle positioning sensor?

 

Doesn't read like a TPS issue, and that would effect operation warm or cold.