^^^ This is indicative of flooding, and right at the top of the list of common causes on engines of your vintage would be caused by failure of the FPR.

^^^ See the word, "history" and the words "check the FPR to make sure the diaphragm hasn't ruptured" up there?

There is the explanation as to what failure of this part does. Flooding normally = hard start, but the BIG clue/hint/observation to take note of on yours is that it only happens on a warm engine, not a cold start (per your first post).

Never did hear if you TESTED this part BEFORE replacing. If it tested good, I'd have pointed you on to another quick way to check for suspected flooding on a warm engine. With very few exceptions, never buy parts without knowing that the part you are replacing will take care of the concern; it's both a waste of money and time.

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2004 Ranger FX4 Level II, 5R55E, Sonic Blue Pearl

Proudly JAP/RICE free since March 2000

I have a similar problem, only my 04 Ranger runs rough when in neutral with the throttle fully pressed it will only turn 3200 RPM and surges. The exhaust smells like it is running rich. The CEL is on and the code says there is a misfire on cyl 4. When on the highway it seems to accelerate well with no surging or missing. I forgot to mention this is a 3 L engine 2WD auto trans. Could this be a MAF sensor problem?

The computer is not allowing to over rev it in neutral

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1999 Ranger 4.0 and extreme Snap-on tool fetish

I have the same exact same issue on my 96 4.0L. I have replaced the fuel filter, and also cleaned the plug harness at the MAP sensor with de-oxidiser. No improvements so far. I'm going to try the FPR next.

^^^ Suggestion RE FPR....before replacing, after driving, let the vehicle sit for 5-15 minutes and pull offf the vacuum line leading to the FPR. Now smell that line for the presence of gas as well as look for dampness. There should be no fuel odor or dampness/wet, ever. If there is, you've found the reason for hard starts on a warm engine.

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2004 Ranger FX4 Level II, 5R55E, Sonic Blue Pearl

Proudly JAP/RICE free since March 2000

Nice, thanks for the tip. I'll check it out.

my truck did this exact same thing a few years ago. It would run great cold or hot but if you let it sit for a few min it ran like turd till it warmed back up. After wasting hours upon hours fixing not broken parts I discovered that I had a vac leak. Ended up pulling the intake and replacing the gasket. I also did a bunch of other stuff while I was in there but the new gasket fixed my old truck

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Matthew Vogt
96 Mazda B4000
4.0 4x4

If the women don't find you handsome, they should at least find you handy

The gasket at the manifold or at the TB?

Upper and lower intake manifold gaskets. I also changed the valve cover gaskets because why not and replaced the o rings on the injectors and cleaned them again because I was in there but that ultimately was the resolution to my problem. I had tried everything to resolve this problem and finally this fixed it. It took a good day to do it all but I also cleaned in the intake and tb as well as replaced a bunch of other stuff it didn't need simply because I was in there. Spark plugs are way easier to do with the friggen intake out of the way

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Matthew Vogt
96 Mazda B4000
4.0 4x4

If the women don't find you handsome, they should at least find you handy

I've tried to smell around on the FPR hose, but no luck. The conditions weren't warm though. I also found one hose that was a little loose and pushed it on. I then checked around for a vac leak with carb cleaner but no luck. I'm going to carry some carb cleaner in the truck and try it out on the spot next time I have the issue occur...and I'll sniff the FPR hose too.

I know with mine the carb cleaner didn't work. I knew it has to be a vac leak but couldn't find it. I don't remember how we came to the conclusion it was intake gaskets but it was the correct conclusion. Oh and by the way... 2 year it took me to figure it out. Drove me Fricken nuts

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Matthew Vogt
96 Mazda B4000
4.0 4x4

If the women don't find you handsome, they should at least find you handy

I was looking at how to do the upper intake gasket. Seems pretty straightforward, and like you did, there's plenty of "while you are at it" stuff that can be done.

Yeah I replaced a bunch of crap simply because the parts were cheap and it was much easier with the intake off.

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Matthew Vogt
96 Mazda B4000
4.0 4x4

If the women don't find you handsome, they should at least find you handy

Pulled the IAC, used carb cleaner and cleaned it out, let it dry, reinstalled it and let the truck run and warm up. Shut it off for about ten minutes and cranked it up. Still ran rough.
DangerRanger37 - what should I expect the truck to do if I pull the plug on the IAC?

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1994 Ford Ranger
4.0 V6
5spd
Bone stock!

i had the same issue recently vacuum lines cracking and replaced intake gaskets. but in all the mis fire was do to the cam and crank sensor usually starts with one cylinder and then to the next. but i went though changing plugs fuel filter oil iac valve clean the mas flow sensor and it came down to them two sensor cam and crank. these 6 cyl are fun aren't they