92 2.3L Occ'l rough start/Hwy hesitation

[av8boy]

OK. Wit's end.

92 Ranger 2.3L (injected, obviously, with the dual ignition). 180,000 miles. 2wd Sport. I'm religious about starting it up in the morning and letting it warm up before driving to work. Change the oil every 3K miles or less.

Part 1: It has been starting right up in the morning... no change there. However, when the weather is especially hot (I'm in inland northern California and I'm talking 90 to 105+ degrees F), it hesitates AFTER it gets warmed up. For instance, cruising down the freeway at 65 the power just drops off, comes back, drops off, comes back, and then runs normally. I also have to occ'ly baby the engine by slipping the clutch leaving stop signs, etc. This might or might not happen even when it is very hot outside. However, I expect ot see it at least a couple times a week.

Part 2: Common afternoon... I drive 45 miles from work to home and stop at the grocery store before getting home. I'm inside for 20 minutes. I come out and try to start it. Cranks forever and finally starts, but doesn't want to run at first. Lots of gas smell. Runs rough for a few minutes (almost like it's flooded) but I can clear it by revving it a bit for a few seconds.

Note: A/C is not a factor in this. No freon. Recently fixed a leak in the system and charged it with Nitrogen to see whether it will hold (seems to be holding) but no coolant so no A/C.

Done this:
Changed plugs (yes, gapped correctly. Old ones didn't look bad).
Changed plug wires.
Changed fuel filter
Changed coolant and flushed system.
02 sensor and PCV valve 1 year old
Changed oil and filter
Changed air filter
Cleaned throttle body (didn't take it apart... just used approved throttle body clearner in throat)
Checked for vacuum leaks (although can't be certain)
Alternator and serp belt 1.5 years old

Considering possiblity of head gasket (problem worst when hot, etc) but don't see obvious indicators... truck does not leak ANYTHING. No gas/oil/water cross-contamination that I can find in any fluid.

Even tried Marvel Mystery Oil (both gas and oil) and some injector cleaner (but fearful of introducing new problems...)

Obviously I've tried to keep from having to go to someone else, but I've reached about the limit of what I can find working in my driveway. HELP! I gotta believe that somebody's going to say, "Oh yeah. I know EXACTLY what THAT is!"

Dave

[stagefright13]

Mine ran like that for a year. If ya stopped it hot would have to rev it to clear it out. Also would load up in the morning for a minute then run fine. I thought it was the head gasket myself cause I have been using some antifreeze. Now I can't even drive it. So I went thru the entire electical and fuel system. It was the fuel pressure regulator. I almost put a head gasket in too! Not saying this is your problem but they are easy to install and don't cost a ton...

[stagefright13]

Oh BTW a quick way to check for vacumm leaks is to spray carb cleaner on all suspect areas while engine is running. If it stalls or idle goes down you found it. The carb cleaner will get sucked in and richen the mixture. Don't catch your car on fire mind you! Just spray a spot at a time then let it evaporate. Only works with flammable type sprays so be careful.