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sorry to say but if your oil pressure is max 30 according to gauge and DROPS from that on idle; engine is worn or something is wrong.
my 174000miles driver has min.40PSI, at idle it might drop to that.

of course the gauges arent the exact truth but Your oil pressure is too low.

Just did an oil change, and put a qt of Lucas oil in it. now runs ~ 45 psi at speed fully warmed up, ~ 35-38 psi at idle.

That was one of my original thoughts....low oil pressure, so the ICM wasn't getting the signal to fire. As I've read, it has to detect oil pressure while cranking for it to start. Still haven't ruled out low compression when hot - however, I would have also suspected a drop in performance too ... owned other beaters with worn engines, and you could tell when you got off the freeway that the car was dogging it.

In a healthy engine, you shouldn't need lucas, or any other additives. Thickening the oil with lucas is only going to give you a false reading of higher oil pressure. Higher oil pressure in this case is only indicating it's getting more backpressure, trying to move thicker oil.

My vote is for the MAF sensor being faulty. When you cleaned it, were you careful to only use MAF sensor cleaner, and not bend the air flow sensor elements?

The only other thing I can think of, is maybe your fuel pump doesn't like to be re-started after running, if its failing. That's a stretch, but it is possible it won't build pressure if its having issues until it's cool again.

Went out with the fam' to Trader Joe's, came back out and it wouldn't start. :( So went and had a beer at a local pizza parlor and chilled for 30 minutes.

When I cleaned the sensors, they were all very clean - don't think that is the source of the problem.

Agree with the comments about oil/warm engines, but I've run my share of beaters with worn main bearings for many miles on a little thicker oil with no problems on restart....don't think that is the issue here.

However, since I replaced the temp sensor the temp gauge says it IS running warm .... I'm guessing about 220-230. I'm going to replace the T-stat (again!) and do a flush in fill to see if that will get it down to normal operating temps. If not, I'll take it to my trusty indie mechanic.

Cheers,
Mike

Took it to a local indy mechanic. Said it was an O2 sensor and the fuel pump (pressure was reading low...which I knew; about 34 psi) to the tune of $860. O2 sensor made sense.. I could see heat sink issues effecting this. Fuel pump didn't; why would it pump fine 15 min after shut - off, then not pump fine for the next 30 min, then pump fine after that!?

I asked if he could be certain this would fix the problem, and he said no. I only had him replace the O2 sensor.... we will see.

did you already change your fuel filter, if its clogged it might affect the fuel pressure?

Yup - replaced the fuel filter two weeks ago.

Replaced the fuel pump this past weekend and this seemed to resolve the hard start problem, and as a bonus the engine def. has more power; will pull right up to red line at WOT before shifting, before I think it would pull to about 5500 (maybe less).

However, now it idles rough on occasion, and the engine lite goes on and off. Really wish this was either a true OBD 1 or better an OBD II ... instead of this blasted GM OBD 1.5 - I don't have the scan tool to read it. Not sure if it is related (i.e. I did something wrong), or a coincidence that this occurred shortly after I replaced the FP.

I was a little disappointed to see the fuel pressure only go up 4 psi to 36. I paid extra $$ to get a A/C Delco (or was it Delphi?) fuel pump ... whatever it was, it was specified by NAPA to be the OEM replacement. Also had to replace the fuel sending unit as well as all the lines were badly rusted - however, went with a cheaper aftermarket unit on this part.