Hunting at lights when cold

[falconsforge]

My 99 SOHC explorer has developed an interesting fault with the arrival of colder mornings. Starts ok and idles ok at the first set of lights about 100m from home. At the second set of lights approx 1km down the road (the motor is still cold) when i pull up after 20-30 seconds the idle starts to hunt quite strongly. Putting the truck into Park settles the idle. After the truck warms up there is no problems. The problem does not seem to occur in the afternoon when its warmer even though the engine is cold. Morning temps are around 8-10 C afternoons 25-28 C. After the first occurence the CEL light came on but I dont have a scanner to read the codes.

 

[James909]

The codes would definitely help. Go to Autozone and they will read the codes for free. My first thought though is a bad/dirty IAC valve.

 

[falconsforge]

Should mention Im in Australia

 

[corkey]

dampness in the air ?
moisture in the mass airflow sensor, ?
the code is the key,, mine when it gets cold throws the code for the intake air circuit low input , or po112,, and when it does the idle is a bit weird,,

 

[James909]

Yeah I would definitely try to get that code if possible. Is there a whining noise coming from the engine bay? If not than it is probably a lower intake manifold leak. The check engine light is probably on because of the lean condition.

 

[falconsforge]

No whining noise, I do get a ticking sound under load which my reading suggests issues with the EGR valve or manifolds

 

[gijoecam]

If you have the 4.0 SOHC motor, I would highly suspect the lower intake manifold gaskets. While you're in there, swap out the cam chain tensioner and install the oil gallery volume reduction plug included in the 00M12 service kit. Any Ford dealership should be able to get you the kit.

-Joe