Bad idle, stalling on cold start-up.

A

AnthraxBird

Registered
Well, every fall / winter the 97 mark idles funky. A very loopy idle, dropping and raising a few hundred rpms, sometimes stalling, etc. It will happen unless the engine is at full operating temp. I've replaced the IAC twice (it's from Autozone... =/) and little to no difference.

Now, the valve covers slowly leak oil into the spark plug galleys, so I am going to replace the gaskets and plugs and clean it out in there to start out with but I could use other advice if it isnt that.

The car has new Coils and a new IAC with relatively new Motorcraft iridiums. (about 20K on em)

What else could cause a bad idle when the car is cold? IMRC's? DPFE? EGR? Clogged Cats? I could use a little input. Let the diagnosis begin!!!!! :fart
 
Cold idle usually means more fuel and timing. I would start there.

Also the IACV is usually open 100% (or close to it). The valve may be fine but you may have a clogged passage in the throttle body.
 
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Cold is defined by the ECT. During warmup it is more rich. When it's cold enough with a partially clogged passage, it could be TOO rich.
 
Very true. When it's warm, the ECU would usually pull back some fuel and therefore run better. I'll try and seafoam the crap out of it first.
 
Isn't there an intake air temp sensor too? Perhaps it's reading artificialy low temps, and in as the weather cools, it gets so low it doesn't know what to do.
 
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