Hello,
I continue to have cold start idle issues with my 5.0 '90. The engine will not stay started when cold unless you give it gas for a couple minutes. I have replaced the iacv as well as the ecu. The car does not have the air pump, egr, or charcoal canister. The KOEO test gives the following codes:

31 egr
81 secondary air diverter
82 secondary air bypass
85 canp canister purge circuit failure
87 fuel pump
84 egr

What can be done to allow the car to cold idle? Can resistors be used to mimic the missing sensors or is the an issue somewhere else? Any input will help. Thank you

 

Try replacing your ECU's temp sensor. Its the one on the heater hose manifold. The engine does not know it needs to warm up if it does not know its cold.

-Jason

 

Thanks, I will pick one up tomorrow and give it a try.

 

If this works, please let us know. Mine does the same thing but has not been a real issue but would be more convenient if it would idle without giving it gas for the first five minutes. One question: would the E303 cam mine has have anything to do with the lack of idle when cold. Someone suggested that this might be the case but I have doubted this because when warm it lopes but will idle fine.
Jason, thanks for taking the time to share your knowledge on this board..

 

The new sensor did not make a difference. The resistance value is the same as the old sensor. Any more ideas?

 

Have you correctly set the base idle?

 

I have in the past. Can you please provide a link on how to do it correctly?

 

Help me create the "Surging Idle Checklist" | Mustang Forums at StangNet

Here you go.

 

If you don't have power to the heater wires on the O2 sensors it will take a while for them to get hot enough to function correctly.