Issue starting when cold

[diverdwn]

I have a 1998 ford ranger 4 cyl, 5 speed with 133k miles that has an issue with starting when it's cold. There doesn't seem to be an issue when it's warm. I think its due to a choke issue but don't know enough about it to be sure or what to check. When starting it does crank but you need to work the gas pedal for it to continue running until it warms up, then it's fine.

Also, I have noticed that sometimes the motor will rev and then drop to close to shutting down over and over again even if the gas pedal is pressed. It has done this to me at a stop light as well as a parking lot.

The engine light is not on.

I have replaced the Throttle position sensor as well as the Idle control Valve and removed the battery cable so the sensor would reset, and I still have the issue.

What do I try next?

 

[SenorNoob]

I think the closest thing to a "choke" on that new a model is the Engine Coolant Temperature (ECT) sensor. It's a 2 wire sensor connected directly to the computer. Computer controls everything based on that.

Hopefully somebody can explain it better than that.....

 

[RonD]

You explained it pretty good

Fuel injected engines do not have "jets" so a standard choke plate can't be used to suck extra fuel into the engine when it is cold.

So the ECT sensor was added, it looks similar to the temp sender for the dash board temp gauge but it has two wires and the sender only has one wire, that's how you can tell which is which.
The PCM(computer) sends 5volts to this sensor, the return voltage "tells" the PCM engine is cold or warm, if cold PCM runs injectors rich, raises idle RPM and advances the timing, just like the choke plate and step cam did.

You can test this sensor with an OHM meter, if engine is cold, outside temp about 70deg, OHMs should read about 35

Engine warmed up, 200deg, OHMs should read about 2

So OHMs go down as engine warms up.

There would be no CEL if ECT failed in this way, what is happening is that it is "telling" the PCM that the engine is warmed up every time you start it.

So if OHMs are low with engine cold replace ECT sensor.

On the 4cyl I think the ECT is under the intake toward the front.

The '98 also uses OBD II so if you can get a live scan you can see what the ECT is reporting as the engine temp, if it is reporting 200deg when engine is cold.....replace it.

Could also be a wiring issue or even a MAF sensor issue, so don't just replace the ECT, test it.

 

[Road Angels]

Make some one else do the work, take it to an autozone or O'reilys and have them scan it for free, if you dont have a meter or reader, if you get the correct readings from the coolant temp switch, cause you have a meter, then as RonD says something else, check the connector for corrsion some times the seal rings go bad, and let moisture in, rare but free to check

 

[diverdwn]

Solved

Turned out to be the Mass Air Sensor. My brother came over, he is a mechanic, and after a little poking around came to that conclusion. I replaced it, $89 + a $14 dollar core charge at the local parts store. My daughter put it in, took her maybe 5 minutes and now it runs as it should. Started just fine this morning after sitting all night.

Thanks for the helpful advice and tips on where to look!