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Discussion Starter #61 (Edited)
I swapped the MAF tonight. No change. There are times it seems like the idle speed just drops by 200-300 RPM. If I disconnect the IAC valve, it behaves in a similar way. Sometimes when at fast idle, it will move up and down. I took the IAC off, cleaned it again, and oiled the shaft. But, the car was getting too warm for a real test. I swapped in another IAC valve earlier in the year, but the problem remained.

So, might I have a chicken before the egg problem. Is the drop in idle speed the cause or the effect? If it's the cause, then I need to look at the idle control side of things.

So, the question is, what sensors drive the idle speed? Coolant temp is probably one. Air temp, maybe. That's in the MAF, so I can rule that out. Vacuum? RPM? What does the PCM use for RPM readings? What else? Simplistically, does the idle control circuit strive to maintain RPM X at temp Y?

I should probably probe the voltage going to the IAC valve. If it's fluctuating, then the valve is okay and something else is driving that.
 

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Discussion Starter #62
Another go-round today. Replaced PCV hoses and elbows, and the PCV valve. Also, the throttle body and IAC gaskets. Also, the hose on the underside of the intake manifold that connects to the tube going to the DPFE sensor was cracked. So, that got replaced as well. Finally, I replaced the engine coolant sensor.

Fired it up, and no change. Fast idles fine, but won't slow idle until warmed up. Fudge!

I messed around checking vacuum hoses while it chugged along intermittently. Once it got warmed up, it was idling fine. Once it was warmed up, I got a can of carb cleaner and sprayed it where the LIM mates to the heads. Every time I sprayed, the car would stumble for 1-2 seconds. I sprayed cylinders 1,3,4,5,6. Same thing which each one. What the heck??? Is every cylinder leaking? All the intake manifold gaskets were replaced a couple of weeks ago. I checked the LIM bolts I could reach, and everything was tight.

Short of the bolts not being torqued correctly, was else could it be? Is it possible for the LIM to be warped?
 

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Discussion Starter #63
Even when warmed up, the LTFTs (both banks) are in 15-20% @ idle, 10% @ 1500 RPM, and 5% @ 2500 RPM. All indicative of a vacuum leak somewhere. STFTs are in the -5% to +5% range.

It might be time to seek professional help (for the car and me!).
 

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Discussion Starter #64
The shop says MAF. I'm not too optimistic that's the problem, since I put a used one in and it didn't alleviate the problem. What are the odds of having 2 bad ones? We'll see if it runs for them in the morning.
 

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Discussion Starter #65 (Edited)
We'll they confessed today that it wasn't the MAF, but the lower intake manifold gaskets. The "Ford guy" took a crack at them today and declared success. He drives a newer Taurus, so maybe that'll bring me better luck! Supposedly, not stumbling when they spray brake cleaner at the gaskets. That's an improvement. We'll find out in the morning. Maybe this saga will be over.
 

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Discussion Starter #66
RESOLVED: Getting Cranky in the Morning

Well, the last attempt at replacing the LIM gaskets has solved to problem. Been over a week and low temps into the 50s and not a single sputter or stall after starting.

Now onto other problems!
 

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Discussion Starter #68
^ Were you ever getting p0171/174 lean codes?
Nope. Never had any codes, except for a cylinder 3 misfire once last winter. The LTFTs would be around 20%. Don't trip any codes until they reach 25%.
 
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