mercury sable hard to start - sometimes

I have had this problem for the past couple of months with a 1994, 3.8 Mercury Sable. From time to time, after sitting hot for some time the car is hard to start.
It will start eventually, but takes several cranks. It happens usually when weather is hot. Two days ago I gave up and went to the dealer, they replaced the idle control valve, 300 bucks and today I could not start it again. It was around 20C/68F. The idle is a bit rough, tacho neeedle mover up and down a bit. Fuel pump comes on, fuel pressure seems OK, new spark plugs, wires, fuel filter. Until now, there was never starting problem. It starts OK when cold. I am stumped and the dealer has no idea what to do except wanting to replace more stuff at random. No codes in the computer, by the way. Rides well, no stalling or lack of power when running.
Stan
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stig opined in

Is the idle ALWAYS rough.. or just after the problem manifests? and rough as in erratic / missing or hunting for right rpm?
Off the top of leetle pointy head, your symptoms point to a bad fuel pressure regulator.
Next time it doesnt want to start.. let sit a minute key off, then floor accelerator and crank it.
If it starts readily, that is probably the problem.
If it wont start then.. next pump the pedal and see what happens.
Other possibilities:
a flaky Engine Coolant Temp sensor
flaky ignition module.. does tach bounce while cranking ?
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In posted on Thu, 30 Sep 2004 17:01:47 -0400:

That's one thing that bothers me about taking the car to the shop. I've completely stopped making suggestions and giving opinions. I basically say, "My car does this and does that, and it shouldn't." I leave it at that. Then that's a good starting point. When they charge me $300 to replace a part and that doesn't fix the problem, I can bring it back and say, "I still have the same problem." Then they get to try again, but any further "replacement of parts" should be covered by my original $300. I came in to have a problem fixed, not to have parts replaced in a trial-and-error situation.
I ran into that once when having a fuel economy problem. I spent nearly a thousand dollars trying to have the problem fixed and each time I paid again and again to have this part and that part replaced. I was really screwed long, deep and hard on that. I won't let it happen again.
Damaeus
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