Low Idle Speed and Cold Start Stalls

[luvmonterey]

My 1994 XLT is currently experiencing low idle speed at start up and frequently stalls unless I feather the accelerator pedal. Idle seems to be 400-500 RPM. Normally, with a cold start, the engine will idle at about 1100 RPM, and then adjust down to about 600 RPM after a minute or two. Currently, even when warmed up, the idle will remain low when I come to a stop. When the idle speed is low, the alternator gauge shows low voltage and the turn signals run slowly. When I put my foot on the accelerator, everything adjusts to normal. Sometimes, upon engine re-start, the idle speed will be normal, or when idling slowly, something will seem to "click", and the idle will adjust to normal. I have checked the ODB1 codes several times over the last couple of weeks (Key On, Engine Off), and no codes are returned. I hate to just start replacing parts without any codes returned. Any assistance would be appreciated!

 

[MrQ]

Unfortunately what you describe can be attributed to many different issues with a first gen. The OBD1 system is notoriously unhelpful in diagnosing problems.

Could be a bad IAC (Intake Air Control), CTS (Coolant Temperature Sensor), or IAT (Intake Air Temperature Sensor), or MAF (Mass Air Flow Sensor). Could also be a fuel pump or fuel filter (check the rail for 35psi at idle).

I would start with the IAC.

 

[luvmonterey]

Unfortunately what you describe can be attributed to many different issues with a first gen. The OBD1 system is notoriously unhelpful in diagnosing problems.

Could be a bad IAC (Intake Air Control), CTS (Coolant Temperature Sensor), or IAT (Intake Air Temperature Sensor), or MAF (Mass Air Flow Sensor). Could also be a fuel pump or fuel filter (check the rail for 35psi at idle).

I would start with the IAC.

Thank you

Unfortunately what you describe can be attributed to many different issues with a first gen. The OBD1 system is notoriously unhelpful in diagnosing problems.

Could be a bad IAC (Intake Air Control), CTS (Coolant Temperature Sensor), or IAT (Intake Air Temperature Sensor), or MAF (Mass Air Flow Sensor). Could also be a fuel pump or fuel filter (check the rail for 35psi at idle).

I would start with the IAC.

Thanks for the information. When you say Intake Air Control, are you referring to the Idle Air Control Valve? I picked up a new Idle Air Control Valve today, but am holding off on installing it until I get clarification. If I have the wrong part, I will return it. Thanks again!

 

[MrQ]

You are correct, I meant the idle air control valve.

 

[luvmonterey]

You are correct, I meant the idle air control valve.

Thanks for the clarification. I replaced the IAC yesterday, and it seems to have fixed the problem. Thanks for your assistance!