Truck starts but stalls until warmed up.

[VTChavez]

I have 97 ranger that starts fine but will not stay running until engine is warmed up. It’s worse on cold mornings but it will warm up and run fine. It’s throwing codes P0171 and P0174 again. I had the intake manifold gaskets replaced and the IACV replaced and no codes for about a year. Any suggestions? It didn’t start the stalling until after the work was completed. The codes are more recent.

 

[RonD]

Welcome to TRS

You will need to replace the ECT(engine coolant temp) sensor, its reporting warm engine when its actually cold, so you are not getting a Choke mode, rich mix and high idle
Your description is kind of a classic sign of a failed ECT sensor

On a 1997 4.0l OHV engine
Look on lower intake behind thermostat housing you will see TWO temp units screwed into the lower intake

ECT sensor will have two wires, one is a grey/red wire, this is a 5volt sensor, and only used by the computer

The other temp unit is 12volt and used by dash temp gauge, usually has one wire, red/white


You will need to drain some coolant out before removing the ECT sensor

 

[VTChavez]

Thank you RonD for your quick response. I will check this out in a couple of days. This is a big help. Thanks again.

 

[VTChavez]

Finally got around to replacing the ECT sensor. Same problem. Any other ideas anyone?